Will mortar stick to vinyl tile adhesive on a cement basement floor?
 

I'd do a test. Mix up some thinset and put a tile down on each area, glued and nonglued. Next morning pop them up. See what happens.

Thanks for the quote about our liberty! Couldn't agree more with Ben.
For the tile, I assume that there will be a difference in the adhesion- how much adhesion is sufficient?

Call Mepai--I believe the Kerabond when mixed with Keralastic is approved for use over 'cutback' adhesive.

Also using Jiffset floor leveler when mixed with Linewebers latex also will encapsulate cutback.

Check with the manufacturer.---

Scrape as much of with a razor scraper----NEVER use solvents EVER--They soak into the concrete and make bonding tile on top very unlikely.

Thanks for all the great advice! Especially about the solvent, which the apron guys had recommended...:no: I will check with Mepai to see if thier adhesives will work. If not, I will try to rent a diamond grinder with dust collector- I assume these will prevent any spreading of dust. BTW, I used a vibrating electric scraper to scrape off the tiles. I hope we didn't already get asbestos-ized...

Most thinset tile mortars that will bond over cutback adhesive say so on the label. Read the label. Typically a razor-blade scraper is used to reduce the black coating to only a stain. You don't need to rent anything especially anything diamond.:)