Clear silicone caulk is the recommended product for installing glass shower doors. The installer applies the caulk to both the inside and outside of the threshold and side rails of the shower door. Silicone creates a waterproof seal that is mildew-resistant.
Acrylic caulk shrinks and cracks over time. The cracks form channels through which water from the shower leak. Silicone makes a better choice as it remains flexible and resists cracking. Leaks in acrylic caulk trap moisture that encourages the growth of mold and mildew spores.
Before applying silicone caulk to a surface, the installer should ensure it is thoroughly clean. If replacing old caulk, he should remove as much of the old material as possible and clean any soap or lime buildup from the shower and the aluminum trim.
The design of the spout of the caulking tube allows the user to cut it to determine the size of the caulk bead. Once he cuts the spout to size, the user must insert a sharp object through the spout to puncture a second seal that prevents the product from drying while on the shelf. A caulking gun presses the plunger to dispense the caulk. Bathroom caulks are also available in a squeeze tube that eliminates the need for the caulking gun.