The travertine filler is a colored semisolid polyester resin. This is the product that is used to fill travertine at the factory.
What is wrong with the grout joints? While filling holes in travertine is one thing, using this glue for a grout joint is probably not the way to go. It is tricky at best.
If you want some advice give me a call at the office during the day.
800-289-6834.
Here is a link for the travertine filler:
http://www.defusco.com/Glues:-Epoxy,-Polyester,-etc.-Tenax-Travertine-Filler/c82_506/p1981/Tenax-Travertine-Filler---1-liter/product_info.htmlGlad to be of service,Mark