I had travertine installed about 5 years ago. One or two tiles in the highest traffic region of my kitchen have developed small holes. Tonight, one of the holes collapsed to reveal what must be an airpocket in the mortar, as there is a void underneath of a couple of square inches.  I found the product to fill the holes in the travertine, but what do I do about the void in the mortar?  Pack a bunch of thinset in there?  Add floor leveling compound? More Of the travertine patch?

Thanks for the help!!!

ETA:
The more i look at it, the more i wish i had a dentist's mirror. I got in there with a coathanger and poked around, and in the 1/2 " between the subsurface and tile (where the thinset should be) there seems to be a sizable airpocket. The center of it appears to be 2-3 inches and it is  not circular, but extends in a couple of directions in thin "arms" for 4-5" in a couple of different directions.   So, it is larger than I thought initially.  It seems that something ghat pours could really get into the crevasses better. Otherwise I'll just be packing it into the middle section.

If you can vacuum it out pretty good, I would just fill it with epoxy.  How big is the "entrance hole"?  You can get the epoxy that mixes in the application tube as you squeeze it out and fill the void.  I would stop short of filling the entrance hole and leave a small gap there.  Once the original epoxy has set up mic up a new batch (the kind you mix by hand) and add some stone dust that matches the color of you travertine.  Fill the hole with this, just slightly proud of the stone.  When it sets up use a dremel tool to grind it down flush with the rest of the stone.

 

Will be documenting arfcom style over the weekend

I have travertine and have needed to repair the grouting between tiles.  Just slap some grout on there and it will look great.

Grout is made for joints.  It will not hold up to a large void.  For example, as grout joints are large you need to moved to sanded grout.


 

you might be able to just squirt some construction adhesive into the thinset "void", ..then cover over w/ the travertine filler if it'll adhere to it..

If he does that the oils in the adhesive will discolor the tile.  If it were a glazed ceramic tile you could get away with it, though.

yeah, but with the nature of the travertine it probably won't be that noticeable anyway. I'd do that and then leave the surface void to fill with grout. Just a shallow area that would be filled on the surface for looks. You'll never know it is there.

Construction adhesive still compresses.  The grout will crack and fall out in no time.  I vote for a matching sanded grout and be done with it.