Any idea what these white bumps are? Can't seem to figure it out. Is it glue? They turned pink before I bleached it and now it looks like this. Grout removal blade isnt going thru it easily

  • Could be tile spacers, but think they usually plastic. Pink probably was some type of fungus/mould that bleach took care of.
    – crip659
    Apr 3, 2021 at 20:25
  • Could the bumps be part of a mesh backing on a sheet of the tiles? BTW: When zooming in on the picture, it looks like you're chipping the hell out of the tiles. Apr 4, 2021 at 4:28

1 Answer 1


From the way it's wearing, that looks like thinset -- the mortar that is used to secure the tiles to the substrate. However, usually thinset is applied with a notched trowel, so there would be lots of little lines of it, instead of two per (four inch square??) tile. If you can gently chip it away with a flathead screwdriver, that's what it is. Just applied in an unusual way.

If it acts "mushy" or soft and not like a cement product, it might be some kind of caulk or glue that was used for a repair job. It's NOT what's used for initial tile laying, but maybe some tiles fell off and had to be re-attached, and silicone caulk was all the homeowner had on hand, for example.

The pink color could have been mold or algae, which went away after you killed it with bleach.

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