Originally Posted by Burnsy

Has to be a white adhesive, so it doesn't bleed through. The adhesive has to be polymer modified. Use a flexible grout aswell. In terms of sealing, you should be fine to fix, then seal, then grout, then seal again and maybe one more time. Make sure also that you back-butter the tiles to fill in any voids in the travertine, as these holes in the back will soon appear on the face of the tile if you don't. If it is a large format tile, then use a large format trowel.

Don't take this the wrong way, how long have you been tiling and where did you learn. Again, don't take this the wrong way, just interested to know