What to do with the black tar?

[karrlot]

I've pulled ceiling and wall panels out.
I've removed insulation.
I've scraped insulation.
Now I'm left with the black tar/glue stuff that I assume was used to hold insulation in place during construction.
It doesn't appear to promote rust. Do I need to get it off, paint over it, or forget about it?

[EastCoastCB]

Originally Posted by karrlot

I've pulled ceiling and wall panels out.
I've removed insulation.
I've scraped insulation.
Now I'm left with the black tar/glue stuff that I assume was used to hold insulation in place during construction.
It doesn't appear to promote rust. Do I need to get it off, paint over it, or forget about it?

Depends.
Mine was trapping moisture and I got rid of it. Spent a LOT of time doing so!
Its all in my thread somewhere if you wanna take a look at how I got it off. Aircraft stripper, then lots of manual labor with a wire brush on a drill.





A GOOD fan will make things much more pleasant.



This stuff takes it off the best

[jazty]

If it's the rubbery black stuff then any petroleum based solvent should soften it enough to take it off. I spent an afternoon the other day removing a bunch of it from the underside of my bus because there were areas where it was trapping moisture and rusting and I wanted to Por15 the underside. I scraped as much as I could off first (with an air chisel. don't use that for the roof panels, though), then I soaked a rag in Varsol (paint thinner) and wet all of the black stuff. Let the Varsol sit for a moment, then start scrubbing with the rag. If you do a quick scrub and move along to the next panel then the rubber from the last panel will have more time to soak in the Varsol. Keep rotating through them and scrubbing.

Next you'll need to clean the liquified rubber+Varsol off before the solvent evaporates and it sticks again. An industrial cleaner/degreaser such as Zep purple cleaner does the job great.

The whole process does involve some elbow grease, but it's not nearly as difficult as straight up scraping it.

Good luck!

[EastCoastCB]

My bus had two formulations of black tarry goo. The front two rows of panels had simple rubberized undercoating type stuff. THat's the super easy to remove kind and didn't seem to have any moisture trapped behind it.
The stuff on the whole rear of my bus after those first couple rows was this stuff called "asphalteum". Its horrible stuff to deal with.

[family wagon]

I should've tried the aircraft stripper but didn't primarily because I worried it might remove the paint from the panels too. Instead I used a heat gun to soften the stuff and then scraped it off with a 3 or 4 inch metal putty knife (which put scratches in the paint.. in retrospect maybe avoiding the stripper for paint concerns wasn't so bright).

When it's thin like EastCoastCB showed with the wire brush picture I would've reached for the naphtha to solvent wash off the remainder. That stuff is most easily found as "VM&P Naphtha" in a well-stocked paint department. I use it for cleaning all kinds of parts and tools, though I think it does leave some light residue so it's not appropriate for the final clean before painting.

I recently discovered a stiff scraper blade for an oscillating multi-tool and currently using it to scrape away old body seam sealer. I wish I'd had it when I scraped my ceiling clean. The blade I got is just two inches wide but it sure is easy to hold the power switch and let the buzzing do the work!

[Stu & Filo. T]

Originally Posted by karrlot

I've pulled ceiling and wall panels out.
I've removed insulation.
I've scraped insulation.
Now I'm left with the black tar/glue stuff that I assume was used to hold insulation in place during construction.
It doesn't appear to promote rust. Do I need to get it off, paint over it, or forget about it?

I looked mine over very closely & didn't notice any rust or roof leaks so I left it.
Many people here will disagree with that but why disturb something that's working?

[Carytowncat]

Originally Posted by Stu & Filo. T

I looked mine over very closely & didn't notice any rust or roof leaks so I left it.
Many people here will disagree with that but why disturb something that's working?

I share this style. Partly because i need to make an effort to avoid attempts at perfection, and partly because i have so many past experiences with restoring a machine meticulously and then shortly after loosing interest in it. Sure the extra work always gets me a few hundred extra but never enough to pay for my time. As i type i suspect my attempts at doing things meticulously is often a kind of treat for my mind to dig into. Probably win win whichever way to go