As experienced DIYers know, never apply new silicone over old— it won't bond and will peel off fast. For sinks or bathtubs, first remove the old seal completely. Grab a utility knife to scrape it away. For residue, use silicone remover gel and a spatula. Then, wash with soap and water, and rinse thoroughly for a pristine surface.
Mask edges with painter's tape for clean lines and no drips. Prep the cartridge per package instructions: attach nozzle, cut tip at a bevel, load into caulking gun. Apply by pressing steadily along the joint, moving slowly without jerks. Smooth with a wet, soapy finger for a pro finish.
