Yes, Encaustic tiles can be grouted, but it takes preparation in order for the job to be completed correctly. All Encaustic tile needs to be sealed before ever using grout. Microscopic holes will be filled with grout and can't be removed if the tiles aren't presealed. I'm working on this new dark blue color in an unsanded grout, and I believe the project will come together with the correct grout. Here we are matching the field color of the tile, and really want the grout to go unnoticed.