Sealing and grouting encaustic tiles

[Flintstone]

With encaustics yes, and seal the grout.

 

[JMC tiling]

If I'am correct at the back of their brochure they don't recommend dark grouts!!
Even when sealed the sides of the tiles could still accept staining which could frame through to the surface.
By using a dark grout it makes the black tiles look bigger than the white.
I've always used cement grey grout either Ardex c2 or mapei 112 or Manhattan.
These tiles are not encaustic but dust pressed tiles and do accept .03...something moisture. I only seal internally to aid maintenance after grouting.

I think John is correct, the last encaustics I installed the recommendation was to either use white or light grey mapai and not any type of dark grout.