Formed deep inside a hot spring, travertine has a naturally rustic appearance that complements many different decors. Travertine is available in several finishes, which depend upon the way the stone was cut and treated. These finishes not only affect how the stone looks, they also affect how you install it.
Travertine is a type of limestone, made of calcite with a similar structure to other limestones. Instead of forming in shell beds, however, it formed beneath a hot spring. Escaping water vapor left behind trails, tunnels, and holes in the cooling stone, which are still seen after the stone has been cut.
Travertine tiles and slabs can be cut in two ways: one way displays the holes across the surface of the tile or counter, the other way – called cross cutting – displays the holes as long lines or veins in the stone. Cross-cut travertine is usually honed or polished in appearance, and requires no additional steps during installation than any other natural stone.
Travertine cut in the standard direction – displaying the holes – can be finished in a couple of different ways. The factory may polish or hone the stone, grinding down its surface. To give the stone a completely flat, finished look, the holes are usually filled in with colored epoxy, known as “fill”. The fill is usually selected to match the color of the stone, but some very large holes may have areas of obvious fill showing.
Many types of tumbled, chiseled, and rustic travertine are sold with the holes intact and unfilled. Unfilled travertine has a rougher, more unfinished appearance that can be appealing in many settings.
If you choose to use unfilled travertine, be prepared to fill up at least the largest holes with grout during installation. The same holes that give travertine its characteristic appearance also weaken its integrity. By skimming the top of the stone with sanded grout the stone gains strength; to keep the rustic appearance of the stone don’t fill the smaller holes or don’t fill the holes to the top.