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From Wal-mart (fairlycheap) Is really good at softening up undercoating that is hard and brittle. I thought i would give it a try this morning and it softens up the crud and makes it stick to your putty knife and not fly all over making more of a mess. I'm working on my fenders right now and the crud is about an eigth inch thick.
A buddy was over the other day who suggested getting as much of the undercoating off before sandblasting. He said blasting this off would make the black slag i'm using worthless to reuse if I mixed it with so much of this tar/rubber or whatever this 50yr. old junk was made of. Kinda make sense to me. It's nice when something works for a change!
Later...Randy
Thanks for the tip, the entire underside of my truck has the rubber/tar like coating. It was either use a benz-o-matic torch and scrape, or PB blaster softens it(expensize). -4speed
I was thinking of using a gel-type brush on paint stripper (by the gallon at H. Depot is fairly cheap) and then hit the fenders (underside) with a pressure washer. This should get most off before sandblasting.
Personally I like the gel type a little better as it doesn't run off the surface quite so fast. I've found that if you concentrate on small areas at a time (approx 2 sqft) and give the gel time to work (10 to 15 min.depending on outside temp) and then hit it with a pressure washer it works pretty good. Careful with the stuff, it'll burn you if you get it on you.
True aircraft stripper is much stronger than the hardware store stuff sold for stripping furniture. Downside is that it will burn skin easier too. You must neutralize/flush it very thoroughly out of any and all cracks and crevises or it will blister your paint later on.