The longest-lasting sealants are silicones, urethanes and urethane hybrids, he says. Silicone and polyurethane sealants last the longest, Hess agrees, but are also the most expensive and difficult to work with. “They don't tool very well, are hard to clean up and in the case of [traditional] silicone, not paintable.”
What caulk do professionals use?
Acrylic Latex Caulk
What kind of caulk gets hard?
Latex and the older acrylic caulks can become fairly hard. Sanded caulk dries pretty hard also.