I have been playing with the Second Skin 'Spectrum' sound deadener, from my understanding this is a lighter weight/thinner sound deadener than sludge, it is designed to be brushed or sprayed on and I would describe it as having about the same consistency as car underseal, very thick and slightly sandy.

from my playing with it I'd say 2 layers of spectrum it not as effective as a layer of dynamat Extreme but I don't know if that is just a mass thing, how much does a 1gal tub weigh (gross so I can weigh what I have left and see what I have used, it may be an unfair comparison if I have only used half the mass of spectrum as I would have extreme, do you know how much a roll of extreme weighs?). The fact you can slop it in all the rough/uneven and hard to reach areas makes it great though, I have bonded 1" aluminium angle lengths to the rear quarter skin in my honda (to prevent the pannel flexing) and I would not want to have to cut and fit mat around them, slap the spectrum on, work it into all the gaps and it works a treat. I'm finding a small long hair 'radiator' roller from B&Q a very nice way of applying it, much quicker than a brush and easy to load more on. The drying time suprised me, I did the rear quarters on a warm day and the second layer took maybe 35mins to dry (black car in the sun so the pannels were quite warm). Not tried spraying it yet but I would imagine through an undersealing gun it would be a very quick and easy way to thoroughly deaden a car.

I would conclude to say its a very useful and good product but my preference would be to use Mat on the large flat areas that are easy to get to (roof, floors, doorskins that are easy to get to) because IMHO Mat is a quicker and more instant effect (cut to shape, roll it on and thats it deadened) and use the sludge or spectrum on uneven areas (anywhere with double skinned supports and existing sound deadening etc).


One question for Ant: to try and increase the effectiveness of spectrum could I mix it with fine (dust) lead shot to increase mass and see if that helps with the effectiveness. I understand its using silicone oxide (sand) suspended in the liquid to add mass, would lead dust be a suitable additive to increase the mass loading ability of spectrum (I ask because lead dust shot is a very cheap form of fine granulated mass).

Bill - were you testing both sludge and regular spectrum? You say that 2 layers of sludge isn't as effective as 1 layer of extreme, but the review isn't on the sludge?

stupidity corrected ;) I used spectrum, if I have put sludge anywhere else in there let me knwo and I'll correct it :whatever: the spectrum is a kind of sludgy consistency hence my little brains confusion.

lol, no worries mate... I was just left questionning whether the rest of the comments were on sludge/spectrum :)

The problem I found is, how do you know that you've put on a "layer"? They say that 1mm is a layer, which is fair enough, but how do you know you actually have a 1mm coverage all over? The only way I can see is if you actually have 40sq ft to cover, and base your assumptions on averages and measurements by eye. I did find that even with sludge, it was easy to put on a layer that was nowhere near 1mm thick (covered 2 doors and 2 panels (10 sq ft+), and had barely affected the quantity left in the tub, rather than using 25% of it.

Not having a go at your methods .. just saying that it's hard to say "1 layer of this is as effective as x layers of y" if you don't know what you're coverage is - it's the same issue I came up against with my sludge review. If you figure out a clever way around that one, lmk :D

well that is the reason I asked how much does a tub weigh, I know what I have covered and I can weight what is left it the tub to work out what I have used. but yes, working out if you have applied a full thickness layer is a bit tricky.

Loving the idea of lead dust, would that work? Anyone tried it?

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