If you are not used to small jobs, never make the mistake of putting a silicone seal on an old one. It wouldn't stick and would peel off pretty quickly. Before changing a silicone seal, whether around the kitchen sink or the bathtub, you must first remove the old one. Nothing's easier. Take a cutter, and peel off the old silicone seal. If the result does not seem clean enough, you can use a special gel intended to get rid of the silicone seal and a spatula. Once all traces of the old silicone sealant are gone, clean with soap and water. Rinse well.
Protect the edges of the support beforehand with adhesive tape. This will prevent the silicone seal from drooling, and will ensure a regular installation. Prepare your bottle of silicone sealant as indicated on the packaging. Normally, you just have to attach a syringe to the bottle, and cut the end with a pair of scissors, bevelled. The bottle of silicone sealant is then placed in a special gun. You can start applying the silicone sealant. Place the tip of the syringe on the area to be joined, and press gently and evenly on the handle of the gun. Progress slowly without jerking. Once you're done, smooth the joint with a wet finger to remove excess and achieve a smooth effect.
