[jsmedrano]

I am laying a tile floor over the wood subfloor in a small bathroom. Two layers of some sort of vinyl tiie(from the 40-50s) were under 1.5 x 1.5 tiles, and somewhere in there was some burlap (?). There were some intermittent areas of a black, smooth substance on the wood - smooth, but not soft. After installing the test tile, it still had not set the next day and when I pulled it up the black substance had turned into a slime that smelled strongly of campfire smoke. Any idea what this is? It's sticky, almost tarry when wet, but cleans up easily with soap and water. The tile had bonded nicely to the adhesive, but it was just sort of sitting on this layer of slime. I've scraped most of it off and am drying the floor - will apply a good layer of sealer.
I've done several floors and have never had this happen before. The house was built in 1936 by a structural engineer and I bought it from his son. I mention this just to note it has been built amazingly, all the doors still straight, attic and floor joists solid and 'overdone'. I can't imagine the builder would have cut corners on his flooring, but who knows?
If anyone knows what this substance might be, I'd be interested to know. Thanks so much.

[JazMan]

You're not supposed to install tiles over that residue. Remove what is removable down to the subfloor then install a tile concrete backer board, then the tiles.

Jaz