1.The Purpose of Using Different Notched Trowels. The type of trowel used for a particular tile installation depends on the kind of setting material being used and on the size and type of tile being installed. Each installation must be considered individually. There are, however, a few general guidelines to follow in choosing the type of trowel to use for a particular installation. Notched trowels provide a bead (rib) pattern which ensures both uniform thickness of material and full contact with the tile after beating in. Small sized, smooth-backed tiles such as ceramic mosaics do not require as much setting material for bonding as do larger tiles with patterned or uneven backs. Non-absorbent tiles have no suction and therefore require enough mortar/adhesive to grip their edges as well as their backs. V-notched trowels are usually used with mastic adhesives which are not sanded and can be readily compressed when tiles are beaten in. Adhesives are limited to walls, residential, and light commercial floors. Square-notched trowels are usually used with sanded, thin-set mortars because the square ribs of mortar break open easily during the beating-in process and give better contact.

2. Coverage is of the utmost importance. Generally, the more uneven the back of the tile or the larger the lug on its back, the deeper the notch is required. With extremely large or uneven-backed tile, it is often necessary to "back butter" setting material on the tile. This is to ensure contact with all points, full coverage and complete contact with the substrate. Inadequate coverage will result in bond failure and/or cracking of the tiles. To ensure 100% coverage, remove and reinspect several tiles after they have been placed.

3. Set tile while mortar is fresh. It is important to set the tile while the setting material is still "open" (before it has skimmed over). To test for this, place your finger in the setting material which has been spread on the substrate. If no material comes off on your finger, it will not bond to the tile, either. Remove the material on the substrate and apply fresh material. If the setting material has skimmed over, pressing the tile into it may create a mirror image of the tile's back on the substrate, but it will not bond to the tile.

4. Beating in. Always beat in the tile to seat it firmly in the setting material and thus ensure a good bond. A 1/4" x 1/4" x 1/4" square-notched trowel gives 50% contact with the tile, before beating it in. A V-notched trowel gives less than 10% contact if the tiles are laid on the pinpoint ridges of the ribs, so a V-notched trowel requires a great deal more beating in just to get the 50% coverage automatically achieved with a square-notched trowel. The amount of beating in determines the amount of contact between the setting bed and the tile. The more beating in, the better the bond. Check the tiles from time to time during installation, to be sure they have been properly beaten in and that there is a strong bond. Do this by periodically removing a tile and inspecting its back.