How do I tell if dried flooring glue is oil-based or water-based?

Question

I removed vinyl flooring that was glued down (by a previous owner) in the 1990's, and there is a significant amount of dried glue left behind on the concrete floor.

The self-leveler and glue that I will be using for the new flooring has different floor preparation requirements depending on whether the old glue is water-based or oil-based. How do I figure out which it is?

Answer 1

Place a wet rag over an area and then put a pot over the rag to keep it from drying out for a day or so and see if the glue softens up. If it does, it was water probably based.