Alistair
16-10-2007, 07:14 PM
Paint Your Wagon… A Guide to DIY Respraying Cars
This is not intended as a complete and professional guide. This is a guide to painting a car at home. Don’t think any of the steps are optional. If they were I’d be missing them out myself. Believe me, I am as impatient and lazy as the next guy. Probably more so. I am assuming you want to paint the whole of your car or a sufficiently large part of it that you can’t really just go for it with rattle cans and optimism. Painting a car is one of those tasks where everyone has their own way of doing things and what works for one will not for someone else so I’m going to be as general as I can while still being relevant and I’ll advise you not to take too much advice as much of it will be contradictory, best to get out and have a go…
1. Attitude and aptitude
One question you should ask yourself before you even start is “why am I doing this?” One painter’s manual I read once had this as their opening line. Their contention being that if you are painting your own car to save a few quid you will end up with a substandard job and would be better working some overtime or taking a bar job in the evenings to pay a professional to do it. Doing a repaint on your car is a time consuming and often frustrating experience which requires a degree of patience and commitment otherwise you’ll just end up cutting corners and it will show in the finished product. Its also true that this is an art not a science. Theres some people who read every book there is going, practice, do everything “right” and yet still never seem to get a good job. Then there are the guys who seem to be able to use old house paint thinned with turps and their cars come out looking OK. Practice helps but you have to have the feel for it.
2. Facilities
You don’t need a heated booth with airflow management and all the professional mod cons to paint a car and get a good finish. It is getting harder to “get by” without, especially if you want to use the latest modern paints (more of these later) but its quite possible to get a good finish painting in a normal garage at home, so long as you have enough space in it. Within reason its also possible to get an excellent finish spraying your car on the drive at home (and I have even sprayed a car in the street with acceptable results) but be aware that these days people are getting more and more nosey about what their neighbours get up to and more and more concerned about the environment and the effect of pollution on their health and generally being kill-joys (some places now you need a permit to own a caravan at your own house let alone spray cars there…)
What facilities you have at your disposal will affect the paint you use, not the job you do…
http://img.photobucket.com/albums/v221/alistairk/estate/DCP_0345Medium.jpg
http://img.photobucket.com/albums/v221/alistairk/estate/DCP_0371Medium.jpg
If you do have a garage at home and you intend to use this to spray in , it must have good light and ventilation (the former is harder to achieve than the later, which can usually be accommodated simply by opening the door, although that allows dirt and dust to blow in…) Of course you r garage also needs to be big enough. How big is big enough? You need sufficient space that you can walk around the car completely unobstructed. If you can’t then you may get away with spraying the car a side at a time if its not a metallic finish, but realistically with most British domestic single garages you will be spraying on the drive…
Some form of folding gazebo may be an idea to keep the worst of the dust and insect off, but be careful not to create a moisture trap where condensation may form. And you shouldn’t spray outside in the rain regardless of if its in a gazebo or not. Although, once again, I have to admit to having painted a car in the rain… Not the pouring down rain, but still…
With all home resprays the weather is going to play its part whether you spray indoors or out. If the weather is too humid, too hot, too cold or you have a sudden temperature drop over night as is common in late autumn and early winter your paint job may be ruined. Garages are notoriously hard to heat and even harder to cool down. The home painter always needs to plan his painting around the weather.
3. Equipment
You will need the largest compressor you can get your hands on really. This is especially true when spraying metallic or pearl finishes where smooth application is everything for a good finish. You can survive with less than a 150 litre / 3 HP / 15 CFM compressor (again I know a guy who did a nice respray on his car using a £69.99 from Aldi compressor but you really are asking for things to go wrong using the wrong tools…)
You will also need a moisture separator (a.k.a. a water trap) and a pressure regulator. Save a few quid by buying a regulator with a built in trap…
Obviously you’ll need a spray gun, more on these in a moment.
You can make your life a little easier with a DA sander, a rotary sander, an inline sander, a jitterbug sander, and a range of other tools. These are all fairly air-hungry so you will need that big compressor to keep up. This is especially true of the DA sander. Don’t go wild buying every tool in Machine Mart until you know how often you’ll be doing this and how good you are at it. A set of nice comfy sanding blocks is a minimum though.
You will also need your consumables, don’t forget to budget for masking tape, and make sure you use low-tack automotive tape not the cheap stuff from B&Q or where ever. I’d also recommend using masking paper rather than old newspaper as newspaper by its nature is not dye-proof and paint is basically a dye. You can also buy a special static charged polythene sheeting to put up round your garage, this is supposed to attract all the dust and overspray to the sheet and not to your wet paint. I’ve never tried it but it sounds like a great idea.
4. Types of spray gun:
This is getting to be as complicated as any other part of the job. The first thing I will say is you do not need an expensive gun to start of with. 90% of it is in the use of the gun, not the gun itself so a bad painter with a great gun will get the exact same result as a bad painter with an average gun, but the later will have an extra £300 in his pocket.
There are gravity and suction feed guns and within those types there are also HP, HVLP, LVLP and possibly other proprietary technologies in place such as Trans Tech which is a system by DeVilbis. We will ignore the big production painting rigs which have a pressurised pot which feeds the gun via a wet hose.
The first thing to get right is that none of these “give a better finish”. That’s the job of the painter. HVLP and its ilk are there to save solvent, paint, pollution and reduce costs in a production bodyshop. They are not there to give a better finish. In fact many painters claim that you get a better finish with a traditional HP gun. Fir sure a smaller HP gun is easier for your compressor to drive and combined with their cheaper purchase price you can see why they are still very popular on the DIY market.
A decent quality HP gun will be streets ahead of a cheap HVLP gun and often cheaper…
One exception to this is the now infamous “eBay blue gun”. This Italian made cheap spray gun is a gravity fed item which claims to be HVLP (but probably isn’t a true HVLP as the air consumption is fairly low). They sell for less than £20 and the results you get with them are excellent for the money and you’d be hard pressed to find a better spray gun under the £70-80 money.
The choice between gravity and suction spray guns is all down to personal preference. I like gravity feed now (I used to be a suction man, ;) ) for several reasons.
They are usually lighter and thus easier to work with on a big job
You can spray lower down – such as sills, etc. without having to jack the car up
You waste less paint as it is all used
You can see easily how much paint is left in the gun
Some claim they are more manoeuvrable and easier to get into tight spots with
.
There are a few specialist paints such as Barcoat, some primers and heavy flakes which are unsuitable for use in a gravity fed gun. But for the most part you can’t go wrong with one. In my opinion…
5. Terminology
Barcoat – (sealer) an inert paint layer which stops new paint reacting with the old paint under it.
C.O.B. – “Clear over base”. A 2 stage system where the basecoat has the colour and the clear coat applied over the top provided the gloss and protection
Candy – a transparent paint applied over a metallic or pearl base.
Drop coat – a light coat applied quickly to metallic and pearl finishes to even out the colour.
Dry coat – a quick light pass not achieving 100% coverage
Dry spray – insufficient thinners, or paint flashing off before hitting the panel
Flash off – the process of evaporation where the solvents leave the coat of wet paint
Flash time – the time taken for the paint to flash sufficiently for another coat.
HVLP – high volume low pressure: an environmentally compliant spray gun which uses a low pressure application technique to reduce overspray and save paint.
LVLP – low volume low pressure: a never version of the above which uses less air.
HP – High pressure: old tech spray gun.
Matt – a paint with no reflection (AKA Flat)
Metal flake – shards of coloured metal which are applied dry or suspended in lacquer.
Metallic – microscopic flakes of metal and other pigments are added to give a reflective sheen.
Orange Peel – a common defect which gives the paint a “dimpled” finish which looks a bit like the skin of the fruit it is names after.
Overspray – any paint which is not where you want it on the panel.
Pearlescent – (A.K.A. Pearl) Mica or other flakes and special pigments are added to give an effect where the colour shifts slightly in the light.
Reducer – thinners for modern paints.
RFU – Ready For Use. Does not need thinners etc.
Satin – a paint with minimal reflection
Solid – a basic type of paint which has no special “effect” properties.
Tack cloth / tacky duster – special adhesive soaked cloths for cleaning panels.
VOC – Volatile Organic Compound. Bad for the environment apparently.
Wet coat – a slow heavy application of paint. Usually full coverage.
6. Types of Paint
These days there are a wide range of paints out there. Some are getting harder to get hold of due to the 2007 EU paint regulations which will finally close the door on non-compliant paints by 31 December 2007. Some are better than others for DIY use. These are listed in rough order of age.
Cellulose: made from shellac, which is in some way a product of crushed up beetles. If that doesn’t put you off using it nothing will. This is the daddy of all car paints. Its completely organic so high in VOC and pretty much banned from all commercial use except specialist restorers of historic vehicles. It is still available for DIY use for older cars or by claiming a non-automotive use. It’s easy to spray, quick to dry and easy to polish up. Its also the choice of driveway resprays as its quick flash and easy working means you get less insects and dust I nit and you can get them out easily. It buffs to a gorgeous deep lustre. It’s not as durable as more modern finishes, and is not available in all colours and effects. It can discolour with age and it is infamous for reacting with off-brand primers or shrinking filler. It cannot be force dried or catalytically improved. You can spray it with very basic mask. Low toxicity. This paint is non-compliant with the 2007 EU paint regulations although certain exceptions are permitted for “historic motor vehicles”
Acrylic Lacquer (1K): one of the first attempts to improve on cellulose. This stuff also goes way back. It was probably invented by DuPont in the 1930s like everything else seems to have been. Acrylic shares most of celluloses properties except it has better durability, better light fastness, doesn’t yellow so badly and if you buy it as a RFU product it is pretty much guaranteed not to react with any primers, stoppers, etc on your car. Pretty much unavailable now sadly except some custom finishes, industrial applications and clear lacquers. Again, low toxicity, basic mask. This paint is non-compliant with the 2007 EU paint regulations and is technically now illegal to supply for automotive use although industrial and other applications remain legal.
Synthetic Enamel: Funny old stuff this. Goes over most things without reacting, but pretty much anything you spray on top of it will react with it. It can usually be cut & polished when newly applied but not when the paint is fully cured (takes 30-90 days depending on weather). Typically has a bright, glossy finish with little depth. Low toxicity, basic mask. It is derived from coach enamel so no surprises it can also be applied by brush. Typical uses for this stuff now is painting floors and chassis not body panels, but I have painted whole cars in it with good results. Depending on the formulation it can last years without fading or discolouring. Fairly durable too. This paint is non-compliant with the 2007 EU paint regulations and is technically now illegal to supply for automotive use although industrial and other applications remain legal.
MS/HS Basecoat: the basic difference between the two is the coverage and MS is already pretty much obsolete. These are solvent based and thus deemed unacceptable due to VOC by the greenies. They are basecoat only products, they are designed to be over-coated with 2K clear but RFU 1K lacquer does the job just perfectly (within the limitations of 1K clear…) They are easy to apply and pretty much all OE repaints and custom effect paint of the last 10 or more years has been in this material from say a BMW silver to Rage Extreme Flip. Ideal for home use, but best suited to spraying indoors as you cannot sand any bugs or dust out of it without wrecking the finish. Low toxicity. This paint is non-compliant with the 2007 EU paint regulations and is technically now illegal to supply for automotive use.
UHS Basecoat: ultra low VOC version of HS basecoat, uses maximum pigment in minimum carrier. This is the new compliant product. It had to be force dried with heat and airflow. I have not used it but anecdotally it appears more expensive and harder to use than HS basecoats. Low-ish toxicity. It does not appear very suitable for home use.
Water-based / Waterborne: ICI and others have been playing with this for decades. Replace the evil VOC solvent in paint with harmless water. Sadly they had to include a bunch of evil other chemicals for it to work so all is not sweetness and light in the garden. Auto Air Colors do a water based paint which is safe to spray without even a mask (apparently!) but all others recommend the standard HSE gear like air fed masks etc. They all need to be force dried with heat and air movement which causes issues for the home user without a booth. The Auto Air Colors needs to be over-coated with 2K clear (I have asked but got no reply if it is suitable to use 1K lacquer) Although there are apparently water based clears now, I have heard that these are very poor durability so most will still be using 2K clear on them. Toxicity varies, IMO unsuitable for home use.
2K (2 Pack) single stage / direct gloss or clear: 2K was brought out in the 1980s as a high gloss, high durability paint. It is available (for now) as a single stage or direct gloss product for solid colours or as a 2K clear which is applied over HS, UHS or water borne basecoat. It is catalysed by an isocyanate compound which is a cumulative poison which causes cancer. This is absorbed through the skin, the tear ducts, your ears, etc. You have to wear proper full body protection and an air fed mask and visor with hood when mixing or spraying it and also when exposed to the fumes from it curing. It has high durability, high colour fastness, excellent coverage and colour matching properties due to standardised formulations. It does tend to look a bit “plasticky” – especially in direct gloss finishes. It is hard to work with when cured and hard to get a deep lustre to. In some cases this paint is now obsolete but loads of exemptions apply while a decent quality replacement is sought. In my opinion it is not suitable for home use.
Recommendation: Where ever possible I use a HS basecoat with a 1K lacquer. For solid colours I use cellulose or synthetic enamel although you can use COB techniques with solid colours as well if you wish. While many of the older traditional paints are technically illegal there are a number of options including grey imports so we can continue to get hold of these paints.
7. Preparation
80% of the paint job is in the preparation. For the most part, especially with solid colours, you could apply the paint with a bicycle pump and still get a great finish if you prepare well and finish properly.
In most cases you do not need to bare metal the car to get a good finish. The small number (or maybe slightly more) where a bare metal preparation is needed are usually one of the following:
Too much paint on car already due to several previous resprays.
Custom paint application will result in too much paint on car unless starting from a bare base.
Old paint is too weak, chalky, pitted, etc. to provide a sound substrate to paint onto…
You have started work and the new paint reacts regardless of what you try.
Bare-metalling a car is a pain in the backside to do, costs you money and can lead to poor paint adhesion if you don’t work exactly to the instructions on the primers you are using. Make sure your base primer is suitable for use on bare metal. To actually get the paint off all or part of the car you need to use you have three basic choices: chemical, sand or blast.
Chemical stripping
Pro: no deformation of metal, quiet, no excess heat.
Con: chemical burns to skin, any residue can cause paint adhesion problems, messy.
Sanding
Pro: quick, controllable, leaves no residue, doesn’t “melt” or contaminate filler
Con: dusty, heat build-up can deform panels, noisy, vibration causes “white-finger”
Blasting
Pro: quick! Gets everything off. Ideal for heavily rusted areas.
Con: dusty, can leave waves or ridges in panels, noisy, less controllable.
It’s also worth remembering that different types of paint react differently to various stripping methods. Some will clog paper or stripping discs very quickly, some will be resistant to chemical attack, etc.
blasting
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sanding
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chemical
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Any areas with paint shrinkage or other evidence of previous paint reaction should always be bare metalled. Areas badly marked with excess stone chips or rust coming through the paint due to porosity of the old finish should also be bare metalled as a matter of course.
Assuming you are leaving the old paint (mostly) on the car and you have completed and primed your repairs or modifications then you can abrade with a DA or a block by hand. Typically 400 grit is about right. You can usually use a finer grade with 2K paints as they chemically bond to the paint and need less of a “mechanical key” to grip to. Ensure the whole car is rubbed down and be careful of edges or mouldings as you can break through to bare metal here and you will need to re-prime and re-sand.
On cars where the existing paint is in very good condition (why are you painting it then?) you can just use a Scotchbrite pad to knock back the gloss and prime over this.
If the car is old, and/or has previous paint repairs etc then an isolator/sealer like Barcoat is a great idea. If you are using Barcoat you will need to use a coarser grade of sandpaper to do the initial prep with. See the instructions on the can for more details…
http://img.photobucket.com/albums/v221/alistairk/Prefect/DCP_1371.jpg
On a lot of cars, especially those with a lot of repairs or modifications, a spray filler may be used in addition to a high build primer. These products produce a far higher level of material on the panel than a normal primer can and will bury minor defects like severe sanding marks, grinder burr, etc. and help level off the feathered edges of filler. They should be used sparingly and not as substitute for getting the body right before picking up the paint gun.
Once you have your primers fully applied you can rub them out. For this you will typically be using a wet and dry paper about 600 grit. It is essential that you use a block or a board if you are not using a sander. Personally I prefer to work at this stage by hand rather than with a power tool. Be very careful of swage lines, mouldings and panel edges. Some people mask over these at this point. If you do, make sure to clean off any residue of tape adhesive with panel wipe before proceeding.
A guide coat is your next best friend. Grab a black aerosol and lightly dust paint over the whole surface of the car body. Once dry you can sand this off gently with a 600 grit and any low spots will remain black. Treat these with stopper and then locally redo the guide coat until the whole car is as smooth as a baby’s buttocks. You have now prepped your car. Strip all the masking paper and masking tape off, wash and clean everything down and ensure all is dry before re-masking. Now the fun bit starts.
8. Application
Primer can be applied pretty much any old how. This is because you always end up sanding the hell out of it. Your actual paint will be treated far more gently and indeed some products such as basecoats can’t be sanded or worked on at all so you have to get them right “from the gun”.
RTFM. Get the paint data sheet and it will tell you how to mix it, how to check viscosity, how to spray it. Follow those instructions not mine…
After mixing your paint set your gun up right. You want a 6” high fan pattern with is a nice narrow ellipse shape when you test spray on the garage wall or masked up windscreen or where ever. Another tip I will share is to make sure you have plenty of paint mixed. You don’t want to have to stop half way though a coat to mix more paint. Whether you use proper mixing cups with lids or jam jars, always mix up about half a litre of mixed material than you think you will need for a full coat.
Build your paint up lightly, many thin coats are always better than one thick coat. Don’t worry if the first coat does not achieve full coverage and looks patchy. Worry if the third coat does this though!
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Build up the coats as the data sheet says. If you are doing a metallic or pearl finish a drop coat may be recommended. You should back off the pressure, back off the distance from the panel and mix the paint wetter for the drop coat and then literally “throw” it on the car with the gun. This makes all the little particles align and give a more uniform sheen. It also looks like you are the sorcerer’s apprentice or something mad if any one sees you doing it. Do not sand basecoat before applying clear coats or lacquer as you will ruin it.
Build up plenty of clear. The more you put on the more you can polish it up.
If you are using a single stage paint like a solid red or white then make sure you put enough paint on that you can polish up later.
And relax. Everything in your garage (or garden) is now colour coded to your car’s new paint scheme and you’ll have bright coloured bogies for a week. But it’s painted!!!!
9. Finishing
Always leave the paint long enough to cure before finishing. Always leave the paint long enough to cure before finishing. Yes, I said that twice, and I did so because its important. Soft paint will sand faster and not polish up right. And if you try polish before the solvent is evaporated it will only dull off again as the solvent does evaporate.
With cellulose and 1K type paints you should leave the car at least a week before going for the cut & polish. 2K and Synthetic Enamel finishes you can (and will have to) attack earlier. With air dry paints (i.e. not 2K) a lot depends on the weather conditions.
Paint shines when light is reflected off its surface. The best and brightest shine is achieved when the surface is perfectly smooth. All that the finishing process (and indeed the “detailing” that people do) is about getting the surface as smooth as possible for the best reflection.
You need to make a value judgement on the state of your paint. Ideally you want to be flatting it off with 1500 grade wet and dry paper used wet with maybe some fairy liquid as a lubricant. However if you have orange peel or other defects you will have to go at it with 1200 or worse. If you have to go lower than this, to say 800 you will have to apply another coat of clear or paint really, if its just localised damage a localised touch up should be fine. You should work through successively finer grades 1200, 1500, 2000 until the finish is as smooth as it can be. It should be vaguely satin like in reflectiveness and uniform in colour. Any sign of “texture” means our old friend Orange Peel and you need to rub that down more. It should go without saying that you should wash the car down every time you change grade of paper too.
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Once the sanding part of the job is done you can get to the really ace bit, the compounding or polishing. There are a bunch of products on the market to do this but I use Farecla G3 Advanced liquid which has to be used with a rotary mop. You can use the G3 paste for hand application. Keep the mop wet and moving or you will burn the paint very quickly. You may prefer to use a hand product on your first paint job. Once the G3 is done you don’t need to do any more but I am often tempted to use some G10 at this point. The G3 Advanced is a “finishing” product so its designed to produce a finish shine. But its hard to resist the lure of more polishing at this point. Final stage is to apply a hand glaze designed for the job. Do not use a wax, sealer or other products associated with “detailing” for 60-90 days depending on weather conditions as these will lead to microblistering due to trapped solvent which continues to evaporate off for some time (30-60 days typically) after the paint is applied.
10. The alternatives
It is perfectly possible to use aerosol cans to achieve a good quality paint finish – even on a whole car. The cost of all those tins is what puts most people off. If you do buy aerosol cans then buy the better quality ones from a body shop supplier which have a fan shaped nozzle on them rather than the ones from accessory shops which have a round spray pattern and are more prone to clogging, spitting and poor colour matching. I’ve seen some really nice jobs done with aerosols. Just remember to put enough paint on.
There seems to be a bit of a craze for applying paint with a brush or roller again now. These are typically using a synthetic enamel product like Rustoleum or Repaint although you can buy Synthetic Enamel in bulk form a body shop supplier. To me this seems like along drawn our process, but if you can’t spray at all for whatever reason it is a method which has been used to paint cars since the dawn of motoring, so why not. Just don’t expect to be able to skip the preparation phase.
Electric sprayers come and go in popularity. They start about £20 and work their way up. If you are thinking of getting one then make sure it is solvent compatible or its innards will melt when you put automotive paint though it. Many say “suitable for cellulose paint”. Remember you tend to get what you pay for…
This is not intended as a complete and professional guide. This is a guide to painting a car at home. Don’t think any of the steps are optional. If they were I’d be missing them out myself. Believe me, I am as impatient and lazy as the next guy. Probably more so. I am assuming you want to paint the whole of your car or a sufficiently large part of it that you can’t really just go for it with rattle cans and optimism. Painting a car is one of those tasks where everyone has their own way of doing things and what works for one will not for someone else so I’m going to be as general as I can while still being relevant and I’ll advise you not to take too much advice as much of it will be contradictory, best to get out and have a go…
1. Attitude and aptitude
One question you should ask yourself before you even start is “why am I doing this?” One painter’s manual I read once had this as their opening line. Their contention being that if you are painting your own car to save a few quid you will end up with a substandard job and would be better working some overtime or taking a bar job in the evenings to pay a professional to do it. Doing a repaint on your car is a time consuming and often frustrating experience which requires a degree of patience and commitment otherwise you’ll just end up cutting corners and it will show in the finished product. Its also true that this is an art not a science. Theres some people who read every book there is going, practice, do everything “right” and yet still never seem to get a good job. Then there are the guys who seem to be able to use old house paint thinned with turps and their cars come out looking OK. Practice helps but you have to have the feel for it.
2. Facilities
You don’t need a heated booth with airflow management and all the professional mod cons to paint a car and get a good finish. It is getting harder to “get by” without, especially if you want to use the latest modern paints (more of these later) but its quite possible to get a good finish painting in a normal garage at home, so long as you have enough space in it. Within reason its also possible to get an excellent finish spraying your car on the drive at home (and I have even sprayed a car in the street with acceptable results) but be aware that these days people are getting more and more nosey about what their neighbours get up to and more and more concerned about the environment and the effect of pollution on their health and generally being kill-joys (some places now you need a permit to own a caravan at your own house let alone spray cars there…)
What facilities you have at your disposal will affect the paint you use, not the job you do…
http://img.photobucket.com/albums/v221/alistairk/estate/DCP_0345Medium.jpg
http://img.photobucket.com/albums/v221/alistairk/estate/DCP_0371Medium.jpg
If you do have a garage at home and you intend to use this to spray in , it must have good light and ventilation (the former is harder to achieve than the later, which can usually be accommodated simply by opening the door, although that allows dirt and dust to blow in…) Of course you r garage also needs to be big enough. How big is big enough? You need sufficient space that you can walk around the car completely unobstructed. If you can’t then you may get away with spraying the car a side at a time if its not a metallic finish, but realistically with most British domestic single garages you will be spraying on the drive…
Some form of folding gazebo may be an idea to keep the worst of the dust and insect off, but be careful not to create a moisture trap where condensation may form. And you shouldn’t spray outside in the rain regardless of if its in a gazebo or not. Although, once again, I have to admit to having painted a car in the rain… Not the pouring down rain, but still…
With all home resprays the weather is going to play its part whether you spray indoors or out. If the weather is too humid, too hot, too cold or you have a sudden temperature drop over night as is common in late autumn and early winter your paint job may be ruined. Garages are notoriously hard to heat and even harder to cool down. The home painter always needs to plan his painting around the weather.
3. Equipment
You will need the largest compressor you can get your hands on really. This is especially true when spraying metallic or pearl finishes where smooth application is everything for a good finish. You can survive with less than a 150 litre / 3 HP / 15 CFM compressor (again I know a guy who did a nice respray on his car using a £69.99 from Aldi compressor but you really are asking for things to go wrong using the wrong tools…)
You will also need a moisture separator (a.k.a. a water trap) and a pressure regulator. Save a few quid by buying a regulator with a built in trap…
Obviously you’ll need a spray gun, more on these in a moment.
You can make your life a little easier with a DA sander, a rotary sander, an inline sander, a jitterbug sander, and a range of other tools. These are all fairly air-hungry so you will need that big compressor to keep up. This is especially true of the DA sander. Don’t go wild buying every tool in Machine Mart until you know how often you’ll be doing this and how good you are at it. A set of nice comfy sanding blocks is a minimum though.
You will also need your consumables, don’t forget to budget for masking tape, and make sure you use low-tack automotive tape not the cheap stuff from B&Q or where ever. I’d also recommend using masking paper rather than old newspaper as newspaper by its nature is not dye-proof and paint is basically a dye. You can also buy a special static charged polythene sheeting to put up round your garage, this is supposed to attract all the dust and overspray to the sheet and not to your wet paint. I’ve never tried it but it sounds like a great idea.
4. Types of spray gun:
This is getting to be as complicated as any other part of the job. The first thing I will say is you do not need an expensive gun to start of with. 90% of it is in the use of the gun, not the gun itself so a bad painter with a great gun will get the exact same result as a bad painter with an average gun, but the later will have an extra £300 in his pocket.
There are gravity and suction feed guns and within those types there are also HP, HVLP, LVLP and possibly other proprietary technologies in place such as Trans Tech which is a system by DeVilbis. We will ignore the big production painting rigs which have a pressurised pot which feeds the gun via a wet hose.
The first thing to get right is that none of these “give a better finish”. That’s the job of the painter. HVLP and its ilk are there to save solvent, paint, pollution and reduce costs in a production bodyshop. They are not there to give a better finish. In fact many painters claim that you get a better finish with a traditional HP gun. Fir sure a smaller HP gun is easier for your compressor to drive and combined with their cheaper purchase price you can see why they are still very popular on the DIY market.
A decent quality HP gun will be streets ahead of a cheap HVLP gun and often cheaper…
One exception to this is the now infamous “eBay blue gun”. This Italian made cheap spray gun is a gravity fed item which claims to be HVLP (but probably isn’t a true HVLP as the air consumption is fairly low). They sell for less than £20 and the results you get with them are excellent for the money and you’d be hard pressed to find a better spray gun under the £70-80 money.
The choice between gravity and suction spray guns is all down to personal preference. I like gravity feed now (I used to be a suction man, ;) ) for several reasons.
They are usually lighter and thus easier to work with on a big job
You can spray lower down – such as sills, etc. without having to jack the car up
You waste less paint as it is all used
You can see easily how much paint is left in the gun
Some claim they are more manoeuvrable and easier to get into tight spots with
.
There are a few specialist paints such as Barcoat, some primers and heavy flakes which are unsuitable for use in a gravity fed gun. But for the most part you can’t go wrong with one. In my opinion…
5. Terminology
Barcoat – (sealer) an inert paint layer which stops new paint reacting with the old paint under it.
C.O.B. – “Clear over base”. A 2 stage system where the basecoat has the colour and the clear coat applied over the top provided the gloss and protection
Candy – a transparent paint applied over a metallic or pearl base.
Drop coat – a light coat applied quickly to metallic and pearl finishes to even out the colour.
Dry coat – a quick light pass not achieving 100% coverage
Dry spray – insufficient thinners, or paint flashing off before hitting the panel
Flash off – the process of evaporation where the solvents leave the coat of wet paint
Flash time – the time taken for the paint to flash sufficiently for another coat.
HVLP – high volume low pressure: an environmentally compliant spray gun which uses a low pressure application technique to reduce overspray and save paint.
LVLP – low volume low pressure: a never version of the above which uses less air.
HP – High pressure: old tech spray gun.
Matt – a paint with no reflection (AKA Flat)
Metal flake – shards of coloured metal which are applied dry or suspended in lacquer.
Metallic – microscopic flakes of metal and other pigments are added to give a reflective sheen.
Orange Peel – a common defect which gives the paint a “dimpled” finish which looks a bit like the skin of the fruit it is names after.
Overspray – any paint which is not where you want it on the panel.
Pearlescent – (A.K.A. Pearl) Mica or other flakes and special pigments are added to give an effect where the colour shifts slightly in the light.
Reducer – thinners for modern paints.
RFU – Ready For Use. Does not need thinners etc.
Satin – a paint with minimal reflection
Solid – a basic type of paint which has no special “effect” properties.
Tack cloth / tacky duster – special adhesive soaked cloths for cleaning panels.
VOC – Volatile Organic Compound. Bad for the environment apparently.
Wet coat – a slow heavy application of paint. Usually full coverage.
6. Types of Paint
These days there are a wide range of paints out there. Some are getting harder to get hold of due to the 2007 EU paint regulations which will finally close the door on non-compliant paints by 31 December 2007. Some are better than others for DIY use. These are listed in rough order of age.
Cellulose: made from shellac, which is in some way a product of crushed up beetles. If that doesn’t put you off using it nothing will. This is the daddy of all car paints. Its completely organic so high in VOC and pretty much banned from all commercial use except specialist restorers of historic vehicles. It is still available for DIY use for older cars or by claiming a non-automotive use. It’s easy to spray, quick to dry and easy to polish up. Its also the choice of driveway resprays as its quick flash and easy working means you get less insects and dust I nit and you can get them out easily. It buffs to a gorgeous deep lustre. It’s not as durable as more modern finishes, and is not available in all colours and effects. It can discolour with age and it is infamous for reacting with off-brand primers or shrinking filler. It cannot be force dried or catalytically improved. You can spray it with very basic mask. Low toxicity. This paint is non-compliant with the 2007 EU paint regulations although certain exceptions are permitted for “historic motor vehicles”
Acrylic Lacquer (1K): one of the first attempts to improve on cellulose. This stuff also goes way back. It was probably invented by DuPont in the 1930s like everything else seems to have been. Acrylic shares most of celluloses properties except it has better durability, better light fastness, doesn’t yellow so badly and if you buy it as a RFU product it is pretty much guaranteed not to react with any primers, stoppers, etc on your car. Pretty much unavailable now sadly except some custom finishes, industrial applications and clear lacquers. Again, low toxicity, basic mask. This paint is non-compliant with the 2007 EU paint regulations and is technically now illegal to supply for automotive use although industrial and other applications remain legal.
Synthetic Enamel: Funny old stuff this. Goes over most things without reacting, but pretty much anything you spray on top of it will react with it. It can usually be cut & polished when newly applied but not when the paint is fully cured (takes 30-90 days depending on weather). Typically has a bright, glossy finish with little depth. Low toxicity, basic mask. It is derived from coach enamel so no surprises it can also be applied by brush. Typical uses for this stuff now is painting floors and chassis not body panels, but I have painted whole cars in it with good results. Depending on the formulation it can last years without fading or discolouring. Fairly durable too. This paint is non-compliant with the 2007 EU paint regulations and is technically now illegal to supply for automotive use although industrial and other applications remain legal.
MS/HS Basecoat: the basic difference between the two is the coverage and MS is already pretty much obsolete. These are solvent based and thus deemed unacceptable due to VOC by the greenies. They are basecoat only products, they are designed to be over-coated with 2K clear but RFU 1K lacquer does the job just perfectly (within the limitations of 1K clear…) They are easy to apply and pretty much all OE repaints and custom effect paint of the last 10 or more years has been in this material from say a BMW silver to Rage Extreme Flip. Ideal for home use, but best suited to spraying indoors as you cannot sand any bugs or dust out of it without wrecking the finish. Low toxicity. This paint is non-compliant with the 2007 EU paint regulations and is technically now illegal to supply for automotive use.
UHS Basecoat: ultra low VOC version of HS basecoat, uses maximum pigment in minimum carrier. This is the new compliant product. It had to be force dried with heat and airflow. I have not used it but anecdotally it appears more expensive and harder to use than HS basecoats. Low-ish toxicity. It does not appear very suitable for home use.
Water-based / Waterborne: ICI and others have been playing with this for decades. Replace the evil VOC solvent in paint with harmless water. Sadly they had to include a bunch of evil other chemicals for it to work so all is not sweetness and light in the garden. Auto Air Colors do a water based paint which is safe to spray without even a mask (apparently!) but all others recommend the standard HSE gear like air fed masks etc. They all need to be force dried with heat and air movement which causes issues for the home user without a booth. The Auto Air Colors needs to be over-coated with 2K clear (I have asked but got no reply if it is suitable to use 1K lacquer) Although there are apparently water based clears now, I have heard that these are very poor durability so most will still be using 2K clear on them. Toxicity varies, IMO unsuitable for home use.
2K (2 Pack) single stage / direct gloss or clear: 2K was brought out in the 1980s as a high gloss, high durability paint. It is available (for now) as a single stage or direct gloss product for solid colours or as a 2K clear which is applied over HS, UHS or water borne basecoat. It is catalysed by an isocyanate compound which is a cumulative poison which causes cancer. This is absorbed through the skin, the tear ducts, your ears, etc. You have to wear proper full body protection and an air fed mask and visor with hood when mixing or spraying it and also when exposed to the fumes from it curing. It has high durability, high colour fastness, excellent coverage and colour matching properties due to standardised formulations. It does tend to look a bit “plasticky” – especially in direct gloss finishes. It is hard to work with when cured and hard to get a deep lustre to. In some cases this paint is now obsolete but loads of exemptions apply while a decent quality replacement is sought. In my opinion it is not suitable for home use.
Recommendation: Where ever possible I use a HS basecoat with a 1K lacquer. For solid colours I use cellulose or synthetic enamel although you can use COB techniques with solid colours as well if you wish. While many of the older traditional paints are technically illegal there are a number of options including grey imports so we can continue to get hold of these paints.
7. Preparation
80% of the paint job is in the preparation. For the most part, especially with solid colours, you could apply the paint with a bicycle pump and still get a great finish if you prepare well and finish properly.
In most cases you do not need to bare metal the car to get a good finish. The small number (or maybe slightly more) where a bare metal preparation is needed are usually one of the following:
Too much paint on car already due to several previous resprays.
Custom paint application will result in too much paint on car unless starting from a bare base.
Old paint is too weak, chalky, pitted, etc. to provide a sound substrate to paint onto…
You have started work and the new paint reacts regardless of what you try.
Bare-metalling a car is a pain in the backside to do, costs you money and can lead to poor paint adhesion if you don’t work exactly to the instructions on the primers you are using. Make sure your base primer is suitable for use on bare metal. To actually get the paint off all or part of the car you need to use you have three basic choices: chemical, sand or blast.
Chemical stripping
Pro: no deformation of metal, quiet, no excess heat.
Con: chemical burns to skin, any residue can cause paint adhesion problems, messy.
Sanding
Pro: quick, controllable, leaves no residue, doesn’t “melt” or contaminate filler
Con: dusty, heat build-up can deform panels, noisy, vibration causes “white-finger”
Blasting
Pro: quick! Gets everything off. Ideal for heavily rusted areas.
Con: dusty, can leave waves or ridges in panels, noisy, less controllable.
It’s also worth remembering that different types of paint react differently to various stripping methods. Some will clog paper or stripping discs very quickly, some will be resistant to chemical attack, etc.
blasting
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sanding
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chemical
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Any areas with paint shrinkage or other evidence of previous paint reaction should always be bare metalled. Areas badly marked with excess stone chips or rust coming through the paint due to porosity of the old finish should also be bare metalled as a matter of course.
Assuming you are leaving the old paint (mostly) on the car and you have completed and primed your repairs or modifications then you can abrade with a DA or a block by hand. Typically 400 grit is about right. You can usually use a finer grade with 2K paints as they chemically bond to the paint and need less of a “mechanical key” to grip to. Ensure the whole car is rubbed down and be careful of edges or mouldings as you can break through to bare metal here and you will need to re-prime and re-sand.
On cars where the existing paint is in very good condition (why are you painting it then?) you can just use a Scotchbrite pad to knock back the gloss and prime over this.
If the car is old, and/or has previous paint repairs etc then an isolator/sealer like Barcoat is a great idea. If you are using Barcoat you will need to use a coarser grade of sandpaper to do the initial prep with. See the instructions on the can for more details…
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On a lot of cars, especially those with a lot of repairs or modifications, a spray filler may be used in addition to a high build primer. These products produce a far higher level of material on the panel than a normal primer can and will bury minor defects like severe sanding marks, grinder burr, etc. and help level off the feathered edges of filler. They should be used sparingly and not as substitute for getting the body right before picking up the paint gun.
Once you have your primers fully applied you can rub them out. For this you will typically be using a wet and dry paper about 600 grit. It is essential that you use a block or a board if you are not using a sander. Personally I prefer to work at this stage by hand rather than with a power tool. Be very careful of swage lines, mouldings and panel edges. Some people mask over these at this point. If you do, make sure to clean off any residue of tape adhesive with panel wipe before proceeding.
A guide coat is your next best friend. Grab a black aerosol and lightly dust paint over the whole surface of the car body. Once dry you can sand this off gently with a 600 grit and any low spots will remain black. Treat these with stopper and then locally redo the guide coat until the whole car is as smooth as a baby’s buttocks. You have now prepped your car. Strip all the masking paper and masking tape off, wash and clean everything down and ensure all is dry before re-masking. Now the fun bit starts.
8. Application
Primer can be applied pretty much any old how. This is because you always end up sanding the hell out of it. Your actual paint will be treated far more gently and indeed some products such as basecoats can’t be sanded or worked on at all so you have to get them right “from the gun”.
RTFM. Get the paint data sheet and it will tell you how to mix it, how to check viscosity, how to spray it. Follow those instructions not mine…
After mixing your paint set your gun up right. You want a 6” high fan pattern with is a nice narrow ellipse shape when you test spray on the garage wall or masked up windscreen or where ever. Another tip I will share is to make sure you have plenty of paint mixed. You don’t want to have to stop half way though a coat to mix more paint. Whether you use proper mixing cups with lids or jam jars, always mix up about half a litre of mixed material than you think you will need for a full coat.
Build your paint up lightly, many thin coats are always better than one thick coat. Don’t worry if the first coat does not achieve full coverage and looks patchy. Worry if the third coat does this though!
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Build up the coats as the data sheet says. If you are doing a metallic or pearl finish a drop coat may be recommended. You should back off the pressure, back off the distance from the panel and mix the paint wetter for the drop coat and then literally “throw” it on the car with the gun. This makes all the little particles align and give a more uniform sheen. It also looks like you are the sorcerer’s apprentice or something mad if any one sees you doing it. Do not sand basecoat before applying clear coats or lacquer as you will ruin it.
Build up plenty of clear. The more you put on the more you can polish it up.
If you are using a single stage paint like a solid red or white then make sure you put enough paint on that you can polish up later.
And relax. Everything in your garage (or garden) is now colour coded to your car’s new paint scheme and you’ll have bright coloured bogies for a week. But it’s painted!!!!
9. Finishing
Always leave the paint long enough to cure before finishing. Always leave the paint long enough to cure before finishing. Yes, I said that twice, and I did so because its important. Soft paint will sand faster and not polish up right. And if you try polish before the solvent is evaporated it will only dull off again as the solvent does evaporate.
With cellulose and 1K type paints you should leave the car at least a week before going for the cut & polish. 2K and Synthetic Enamel finishes you can (and will have to) attack earlier. With air dry paints (i.e. not 2K) a lot depends on the weather conditions.
Paint shines when light is reflected off its surface. The best and brightest shine is achieved when the surface is perfectly smooth. All that the finishing process (and indeed the “detailing” that people do) is about getting the surface as smooth as possible for the best reflection.
You need to make a value judgement on the state of your paint. Ideally you want to be flatting it off with 1500 grade wet and dry paper used wet with maybe some fairy liquid as a lubricant. However if you have orange peel or other defects you will have to go at it with 1200 or worse. If you have to go lower than this, to say 800 you will have to apply another coat of clear or paint really, if its just localised damage a localised touch up should be fine. You should work through successively finer grades 1200, 1500, 2000 until the finish is as smooth as it can be. It should be vaguely satin like in reflectiveness and uniform in colour. Any sign of “texture” means our old friend Orange Peel and you need to rub that down more. It should go without saying that you should wash the car down every time you change grade of paper too.
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Once the sanding part of the job is done you can get to the really ace bit, the compounding or polishing. There are a bunch of products on the market to do this but I use Farecla G3 Advanced liquid which has to be used with a rotary mop. You can use the G3 paste for hand application. Keep the mop wet and moving or you will burn the paint very quickly. You may prefer to use a hand product on your first paint job. Once the G3 is done you don’t need to do any more but I am often tempted to use some G10 at this point. The G3 Advanced is a “finishing” product so its designed to produce a finish shine. But its hard to resist the lure of more polishing at this point. Final stage is to apply a hand glaze designed for the job. Do not use a wax, sealer or other products associated with “detailing” for 60-90 days depending on weather conditions as these will lead to microblistering due to trapped solvent which continues to evaporate off for some time (30-60 days typically) after the paint is applied.
10. The alternatives
It is perfectly possible to use aerosol cans to achieve a good quality paint finish – even on a whole car. The cost of all those tins is what puts most people off. If you do buy aerosol cans then buy the better quality ones from a body shop supplier which have a fan shaped nozzle on them rather than the ones from accessory shops which have a round spray pattern and are more prone to clogging, spitting and poor colour matching. I’ve seen some really nice jobs done with aerosols. Just remember to put enough paint on.
There seems to be a bit of a craze for applying paint with a brush or roller again now. These are typically using a synthetic enamel product like Rustoleum or Repaint although you can buy Synthetic Enamel in bulk form a body shop supplier. To me this seems like along drawn our process, but if you can’t spray at all for whatever reason it is a method which has been used to paint cars since the dawn of motoring, so why not. Just don’t expect to be able to skip the preparation phase.
Electric sprayers come and go in popularity. They start about £20 and work their way up. If you are thinking of getting one then make sure it is solvent compatible or its innards will melt when you put automotive paint though it. Many say “suitable for cellulose paint”. Remember you tend to get what you pay for…