The type of adhesive you use depends on where you're tiling, what you're tiling on, and how experienced you are at tiling.
Thinset mortars come in powder form and must be mixed with either water or an acrylic additive. (Some powdered thinsets have an additive already blended in.)
Thinsets have a stronger bond and are more flexible than pre-mixed adhesives. They can also support a lot of weight, so they're often used for floor installations.
Thinsets can be used in wet areas as well as those exposed to heat. Thinsets are often available in dark grey or white. If you’re using a light-colored grout, it’s a good idea to use the white thinset.
To mix thinset mortar pour a small amount of water (or liquid additive, if desired) into the bottom of a large bucket, then pour in the powder. (Using the liquid first will help cut down the dust. But we still recommend wearing a respirator when mixing thinset.)
Begin mixing the material with a margin trowel to get the liquid worked into the powder. You CAN continue mixing with the margin trowel, but if you have access to a ½-inch drill, we recommend using the drill and a mortar-mixing paddle attachment.
When using a drill, run the drill at a slow speed to avoid mixing air into the mortar (which will make it weaker).
We like mortar to have the consistency of thick peanut butter. If you scoop some up with a margin trowel it shouldn’t drip off the trowel on its own, but you should be able to shake some of it off.
Most do-it-yourselfers will find themselves adding a little water, then a little mortar, then a little more water, and so on, to zero in on the right consistency.
When you’re done mixing, let the mortar sit for ten minutes. This is called “slaking.” It allows moisture to penetrate any remaining lumps of powder and it allows the additives to activate. After ten minutes, give the mortar a quick final stir and it’s ready to use.
Pre-mixed adhesives are good for setting wall tile because they start gripping the tile even before they're fully cured.
Adhesives can be used in areas that may get slightly damp (such as the wall tiles in a shower surround). Adhesives should NOT be used in areas that will be exposed to prolonged moisture (such as the floor tiles in a shower or bathroom.)