Organic mastic is a material for bonding shower and bath tile that cures by evaporation. This type of adhesive is suitable for installing ceramic tile on interior floors, walls and granite countertops. Organic mastics are purchased premixed; no further addition or liquid or powder additive is needed. There are two basic types of organic mastic. Latex-based mastics contain water; petrochemical-based mastics contain a solvent called toluene. Each type is made up of two components; a bonging agent and a mixing agent.
Do not use a petrochemical-based mastic to set finished marble; the chemicals will discolor the stone. Latex-based organic mastics and any of the thin-set adhesives can be used with stone tile products. Because organic mastics are premixed, they are the easiest and most commonly used adhesives for residential use and remodeling. they are especially popular for use on walls because they hold tiles as soon as they are set in place, eliminating tile slippage. Mastics can be used in dry installations with plywood, wallboard, plaster, portland-cement mortar, formed concrete and masonry substrates. Not all mastics are compatible with all substrates so check product labels.
Organic mastics can be used in properly prepared wet areas, though considerable care should be taken if applying a mastic in a heavily used wet area such as a shower or bath in an area like San Antonio where the climate can add to the project's length of time. Organic mastics are not suitable for use around swimming pools or in exterior remodeling jobs. Check product labels for appropriate uses of individual brands.
Despite their ease of use and popularity, organic mastics are inferior to thin-set adhesives in a number of ways. They do not have the bond strength or flexibility of thin-set in most cases.
Use caution when performing a remodel job with organic mastics. The vapors in petro-chemical-based mastics are flammable and dangerous when inhaled - take proper precautions and always keep children and pets away from any job site in your home. Mastics are sold in cans. There may be some oil or water floating on the surface when the can is opened for the first time, similar to paint. If the mastic is difficult to stir, it may be too old to use and should be returned. You can store leftover organic mastic in a cool, dark place but it does not keep very well, even in a properly sealed can, so try to purchase only the amount needed to save money.
Clean tools and mastic spills as soon as possible, while the mastic is still soft. Hardened mastic is nearly impossible to get off. Remove solvent-based mastic with paint thinner; for water-based mastic, use water.