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Expanding Foam - Do's, Dont's and Dangers


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#1 Blade

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Posted 05 Jan 2004 - 22:13

Expanding Foam - Do's, Dont's and Dangers

There is an old saying amongst Sailors and Fisherman... "A man should always maintain a healthy respect and fear for the sea"


The same is true for Expanding Foam. It has the capacity to do an exceptionally good job of both soundproofing, and panel deadening in an Automotive environment, but with the same stroke, it is also able to make a real mess of a car or van, and also ruin your clothes, and make you look like a leper for weeks to come

Despite the risks (which can be reduced or eliminated: explained later in this guide) Expanding Foam can deaden a vehicle in a way no other product can. Myself, and many others have been astounded by the gains in volume achieved by it, and the reduction in “bad vibrations”

I will attempt to explain some of the advantages, disadvantages, and issues pertaining to the use of Expanding Foam, here.


Where To Get It?

Expanding Foam is available from most DIY stores, as well as the obvious B+Q/Focus/Do-It-All chain stores, or online from places like ScrewFix. It comes in an aerosol can, usually with a separate nozzle, which is attached to the top of the fan on purchase. The particular brand I used was packaged with a large nozzle, for filling large spaces, and a smaller one, for detail work.

It should come in a can looking something like this, and cost around £5 for a can… A hell of a lot cheaper than deadening sheets! 2 cans should be enough to comprehensively do the whole bootlid of a single vehicle.

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You do however, need to choose the sort of foam you want to use... You have a choice between regular Expanding Foam/Gap Filler, or Grip-Foam. The main difference is in the expansion size. Regular foam will expand to around 5X its initial volume, whereas Gripfoam only blows up to about 2X its starting size. Gripfoam also seems to set more solidly, and have a higher density afterwards… which is always good :) Personally, I preferred to use "GripFoam"... works pretty much the same, but also makes usage a little more predictable! :)



Benefits of Expanding Foam

When used effectively, Expanding Foam is capable of doing a superb job of cutting down panel vibrations caused by heavy-weight audio systems, at a much smaller cost than sound deadening sheets. Also, whereas deadening sheets area heavy, causing some worries for those looking to minimise weight in high-performance vehicles, Expanding Foam is extremely light.

Sound deadening sheets, such as Dynamat, Dynamat Extreme, and Brownbread, attach to body panels, increasing their weight, lowering their point of resonance, and giving enhanced structural rigidity. However, short of using many many layers, there will still exist large open expanses within the vehicle’s skin, most importantly inside the boot lid, but also between the inner and outer door skins, and in the rear quarter section of the vehicle.

These open areas are prime space for sound deadening material, and this is where Expanding Foam comes into it's own. It will contact with the inner and outer skin of the vehicle, and if used in this way, will pull panels together, and hold them apart as they attempt to resonate in either direction.

Result… Solid as a Rock! :D


What To Expect

After a comprehensive going over with Expanding Foam, you will notice several benefits. Firstly, cabin gain will be dramatically increased- no longer will sound waves be wasted oscillating the rear boot lid, but instead will be reflected back into the vehicle. Also, from the outside, audible vibrations are reduced by a great deal... which as we all know, is a battle we all have to fight! :)

What I found, was that Expanding Foam does not really absorb much sound at all, in the same way as stuffing boot lids with Rockwool, or Pink Panther Loft Insulation. Instead, it forms what I can only describe as a several inch thick “wall” in there… braced either side with the interior and exterior skin of the car. This solid wall, bounces a whole lot more sound back into the cabin. I was seriously impressed with the results after usage… volume in the cabin seemed a hell of a lot louder

However, Expanding Foam also does a good job of removing a lot of the “mellowness” from low octave sound. This may be a good, or bad thing, depending on what your aims are. Responsiveness seemed to have improved, with what seemed like less of a delay on bass sounds. There was also a perceived increase to the accuracy of what the sub produces, with bass notes ending more precisely, sounding less “laggy”, with all the sloppiness taken out. However, after a good deal of listening, I found that many of these characteristics added to the sound, and smoothed it over quite nicely… when this was gone, bass had a tendency to sound a little hollower, with less associated warmth. I’m sure this could be solved by using a little less foam, and would be less of a factor with a ported box, but for my personal preference, I loved the volume increase, and improved tightness, with cabin gain increased to truly evil levels :D


Safety + Preparation

Now, the most IMPORTANT part of this section... Safety and Preparation. As I mentioned before, if your not careful, Expanding Foam can be truly evil stuff, so there a number of precautions and procedures you should go through first. Gloves are vital if your gonna play with Expanding Foam, if you get the stuff on your hands, you won't be a happy chap, it'll stick, and won't come off = you looking like a leper. More on that later… Suitable clothing is also a must, don't wear anything you intend to wear again, if your get this stuff on your clothes, its gonna make a mess, and , you guesses it, it ain’t coming off. If it does contact skin, in p[particular your hands, you’ll have to wait for the top layer of your skin to peel off before you can get rid of it :chunks: This is what you’ll end up looking like, if you don’t use gloves:-

Posted Image

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Bear in mind… that stuff don’t come off…

<Images Courtesy Of LethalForumula>


Also, if your too lazy to remove all equipment out of your boot, be sure to cover it with a dust sheet. I CANNOT stress how sticky this stuff is, and how difficult it is to remove, should it come into contact with anything it's not supposed to.

Only possible way to remove it, is with white spirit based solvent, and this is only possible to do before it sets.

Some people find, that due to the drainage holes in the boot being blocked up when using Expanding Foam in the boot lid, rear windows can get a bit steamy… you can stop this by running tube through the drainage hole before beginning, and using the foam around it. I had no problems with this personally, but it may be worth considering :)

Use Expanding Foam in a ventilated area, not in a small enclosed space like a shut garage. Expanding Foam iso-cyanates, which can damage lungs… If your really worried, wear a mask.

Also a good idea to get a feel for using it before you let a can loose on your car… Have a play with squirting varying amounts onto a wooden sheet or something you can throw away to see how much it’s gonna expands before you use it for real. A good test of control is writing your name in the stuff… also great fun to see it expand into a big mess after 10 or 15 minutes :)


Firstly, you wanna clean the area you want to use the foam on... a damp cloth should be just fine, just to remove dust and dirt. No need to dry it off completely afterwards, a little moisture will do no harm... the foam needs moisture in the air to expand anyway. If you are using the foam on a particularly hot dry day, a few squirts into the air with a mist-type-squirty-water bottle will help it to expand properly.



Using Expanding Foam

Next, choose which nozzle your gonna use... large or small. Personally, I like to do the whole thing with the small one, takes a little longer, but the extra control is nice.

The foam will initially expand a fair amount when it leaves the can, within the first 10 or 15 seconds, however, bear in mind that expansion will continue for about 30 minutes, and can be difficult to predict. By adding bit by bit, with 10 or 15 minute intervals in-between, the risk of having the stuff oozing out all over the place is reduced ;) Adding a whole can in one go, is not a great idea, and the rapid expansion can buckle larger panels!

1-3 second bursts work well… wait for 30 seconds or so between squirts to judge expansion.

Your aim should be to fill the expanse you need to as completely as possible... One problem you may find though, is doing the area either side of the rear window, on each side of the boot lid. Ideally, this whole area should be filled, all the way up the sides, upwards towards the high-level brake light. This isn't easy, without havint a 30 inch nozzle on the can to get all the way up there! But there is a trick to it: Fill the corners, either side of the boot lid, and wait for it to set. Once its hard, poke a hole through with a screw driver, and insert the nozzle through the hole. Squirt through to your hearts content, and the foam will expand upwards through the side pieces, and give you fully deadened sections, either side of the rear window

The foam should be used to fill large expanses as thoroughly as possible, feel free to stop every so often for a break to let the foam finish expanding, before resuming. The new foam will fill in the gaps left during the previous session, and as the previous stuff has already expanded, you'll know your not adding too much, and risk getting it everywhere.

For optimal results, for example in a vehicles boot-lid, I’d recommend a combination of Expanding Foam, and sound deadening sheets/Marley tape yields best results. This involves deadening body panels as normal on the outer skin, then using Expanding Foam to fill the large open space, then covering the inner skin with another layer of 2 of Dynamat, or similar product, to create a sealed “wall” of deadening, with a strongpoint on either side.


If done correctly, the results are really impressive :)


Best of Luck Gents… Have fun!

#2 Matt

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Posted 05 Jan 2004 - 22:20

Nice, that fits in very well with the 'tuning the accoustic environment thread' that I'm in the process of writing. A good thread chap :)

I have to say I've not been able to get it off with white spirits though, never worked for me - acetone every time :)

To aid curing you can spray water onto the area prior to application. This also help it stick (bizarely) which is handy if working upside down.

:)

Hoping...


#3 tej

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Posted 05 Jan 2004 - 22:21



[b]There is an old saying amongst Sailors and Fisherman... "A man should always maintain a healthy respect and fear for the sea"



The same is true for Expanding Foam.


LMAO!

gr8 post.. needs to be FAQ'd

#4 Ghost

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Posted 05 Jan 2004 - 22:22

Nice write-up! Gonna have to invest in some of this I think, my car has a myriad of small places that are gonna prove to be a nightmare to brown-bread, so this may be a life-saver.

Adam

#5 Blade

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Posted 05 Jan 2004 - 22:26

It's definitely worth it... cars are full of empty expanses, just asking to be filled up without deadening. Unless you fancy using layer upon layer of sound deadening, expanding foam is pretyy much the only way. Even so, deadening sheets are still unable to hold the inner and outer skins together in this way, deadening flex in either direction

#6 James.

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Posted 05 Jan 2004 - 22:33

woo... my hands are famous!!! :)

just a note though, but even when still wet white spirit seemed to do nothing at all..

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#7 AaronM

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Posted 05 Jan 2004 - 22:37

Brilliant Blade FAQ material!

I saw blades car at MK meet and opened and shut the door numerous times and it felt solid as any german car, owning a french car i know how flimsy they are!

His tailgate was solid! i hit it numerous times and it just wouldnt dent ;)

#8 Blade

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Posted 05 Jan 2004 - 22:43

Stop trying to beat up my car! :D

Incidentally, if anyone feels the need to click the Rep button to the left, it wouldn't go unappreciated ;)

#9 AaronM

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Posted 05 Jan 2004 - 22:45

Im looking right but i cant see a rep button :P

#10 puggie

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Posted 05 Jan 2004 - 22:53

Nice little write up, I'm taking note as the Pug is getting deadened!
Triple point

The triple point of a substance is the temperature and pressure at which three phases (for example, gas, liquid, and solid) of that substance coexist

For example the temperature and pressure of my arse during a bad fart after a good curry!

#11 Scott G

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Posted 05 Jan 2004 - 23:06

Thats my next job sorted then, working nights and expanding foam during the days.

FAQ tastic.
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#12 Mr Bump

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Posted 05 Jan 2004 - 23:23

I suppose we should have taken some pictures when I had an "incident" filling some holes in the mini.

Lets just say they nozzle went bang, expandy foam came out at an alarming rate until I shoved the can in the spare wheel well LOL

Unfortunately the afore mentioned "bang" had covered the front end of the car behind the mini with wet sticky foam.

The car in question was the ECC Volvo and it was being picked up by its new owner in an hour PMSL

Out came the thinners and the rags an we cleaned every last bit off apart from one small lump on the intercooler LOL

Aaah . . . memories ;)

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#13 somouk

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Posted 06 Jan 2004 - 00:19

That a brilliant teaching guide there blade. I think it should definately go in the FAQ. It could save a lot of the SQ guys some money on sound deadening and new clothes!

Mart

#14 Woosey

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Posted 06 Jan 2004 - 00:55

dont forget how good roof insualtion is;)

RIP HB


#15 Boxer_IVE

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Posted 06 Jan 2004 - 02:36

I have to say I've not been able to get it off with white spirits though, never worked for me - acetone every time :)

To aid curing you can spray water onto the area prior to application. This also help it stick (bizarely) which is handy if working upside down.

:)


Does acetone work on cured foam? I've got a small sample that I've bombard with all sorts and it refuse to die. There's still some blocking my sink too so it drains slooowly. Lesson learned there, never try to wash it off your hands!! What Matt said about the water, whilst bizzare, is very true and a sink's drain is the ideal place for it to stick and cure!! :(
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#16 Snake Racing

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Posted 06 Jan 2004 - 02:36

Roof insulation or Expanding foam ..... Hmmm :confused:
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#17 Woosey

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Posted 06 Jan 2004 - 02:39

Roof insulation or Expanding foam ..... Hmmm :confused:

personally having used both i would go with roof insualtion pack it in REALLY tight till you cant get anymore in. advantages are that you can take it out again and it doesnt create a mess!!!

also £3.90 gets oyu 10meters of the stuff which is LOADS!

RIP HB


#18 Matt

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Posted 06 Jan 2004 - 02:40

I haven't tried it on cured foam, but a mate has one of the special guns you can use, and a can of special cleaning spray, it worked a charm when the foam was damp, but he said if you left it to dry too long the only way you can clean the nosel is mechanically...so I guess not.

On the other hand, have you tried brake cleaning spray - I use it for everything and it generally does the trick :)

Hoping...


#19 deano vw

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Posted 06 Jan 2004 - 02:55

personally having used both i would go with roof insualtion pack it in REALLY tight till you cant get anymore in. advantages are that you can take it out again and it doesnt create a mess!!!

also £3.90 gets oyu 10meters of the stuff which is LOADS!


sorry to go O/T, well it aint really, sort of ;)

where did you get this from bud, also does it cause any irritation to the skin or anything?

i need something to block up all the really big gaps in the back of my golf, as well as behind the door cards in the back of the car

also, is it flammable?

TIA :D
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#20 Woosey

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Posted 06 Jan 2004 - 02:57

got it from b+q yes it does cause irritation, get some gloves and a mask!!! its not flammable though (we were pointing hte heat gun at it too, when it was set to 550 degrees;)

RIP HB