Unlike thinset adhesive, mastics don't need any mixing. But they do not provide the same bond strength or water resistance as thinset. Mastics are sticky adhesives that consist of a bonding agent and a carrier. It evaporates as the mastic cures. Open the bucket, stir the glue if it appears to need it, and you're ready to trowel.
Mastics also can cost a bit less than thinsets.
But you can't beat the versatility and long-term performance of thinset adhesives. As a group, thinsets stick to most substrates, including mortar setting beds, concrete slabs, tile backerboards, drywall, plywood and even existing tile or plastic laminate. When paired with the right substrate, most thinset adhesives can be used indoors or outdoors in wet or dry areas. Most also work well in areas exposed to heat, such as behind woodstoves or over radiant-heated slabs. Mastics typically are recommended for use in dry interior locations not exposed to heat, although Type I mastics are approved for intermittent water exposure.