Black Mastic?

You say it disolves in paint thinner? That could be your answer.

Liquid Sandpaper takes the stuff up quite nicely. I just did this in a kitchen remodel. Not wood floors, though. Concrete slab.

Open all the doors and windows and put a floor fan or two in the room. Ventilate. Ventilate. Ventilate. Have lots of rags and empty coffee cans available. Turn off any pilot lights, and of course, don't smoke.

Wear heavy, acid-resistant rubber gloves and expect to throw away your clothing when you're done.

-Frank

Scraping or Sanding WILL do! It ain't pretty or pleasant, but it will do.

PJ

Be careful not to burn down the house. A few painters just did that recently in NC.

Use the film covering clothes from the cleaners over the area with the paint thinner to prevent evaporation while it is soaking in.

You can try the trick of using some dry ice and then scraping. Remember to have ventilation as CO² is not poisonous, but it can replace the oxygen in a small room. You place the dry ice on an area, and get it cold enough to make the stuff brittle. Trial and error at finding the time needed.

Don't sand, this stuff likely contains asbestos fibers as a binder.

-Dave

HD sells Jasco Adhesive Remover in their flooring dept. It works quite well without the 'explosiveness' that paint thinner (or similar) may present.....

Brush it on, let it set for a few minutes, attack it with a 2" scraper and scoop the remover and adhesive up, scrub with Comet/Ajax then sponge with clear water....

I'd avoid sanding as this black mastic *may* contain asbestos. Which of course is primarily hazardous if the fibers get airborne....

HTH

Rick

No mentioned in passing :

Nope, because then the black will seep down into every little crack. I found a gel that seemed to lift it up, but until I sand it tomorrow I am not sure it will work.