• Caulk is used around the shower valve.shower handle image by Leticia Wilson from Fotolia.com
  
  Caulk is a semi-flexible substance used to fill expansion gaps in the shower. These gaps occur wherever two surfaces meet in a 90-degree angle, including the tile and tub, wall tile and shower floor and in the case of glass or fragile tiles, the corners of two walls. Caulk is also used to fill in the gaps around tub spouts, shower valves and shower head arms, creating a watertight seal.
  
  

Remove and Clean

• Caulk needs to be replaced fairly regularly. Because caulk must flex, it is normally a soft material. When it ages, it also dries, causing it to crack and come loose. If this happens, it needs to be removed completely and redone.
  
  The fastest way to remove caulk is to cut through it with a sharp utility knife. Make two passes with the knife, one at the bottom of the caulk and one at the top. The knife should be touching either the tile or the tub as you scrape. Pull the cut pieces of caulk out in long chunks and clean the interior very well with rubbing alcohol or mildew cleaner before applying new caulk.
  
  

Use the Right Caulk

• Caulk comes in a variety of colors and substances. Look for a caulk made for the size joint you have. Caulk with sand in it is used for large joints of 1/8 inch or larger. Latex caulks are available that match the colors of the tile grout, and are easy to clean up after. You can also use silicone caulk, although this caulk is harder to spread evenly. If your tub is mildew prone, use an acrylic caulk that is mildew resistant, which will help impede its growth.
  
  

Use your Finger

• Whether you use a caulk gun to apply the caulk to the joint, or you open the back of the tube and scoop some out, you'll need to smooth the caulk into place. The easiest way to get a clean caulk line and tight seal is to use your finger.
  
  Dampen your index finger slightly, and press it into the caulk bead. Smooth it as you go, pressing it firmly into the tile or tub and packing it into deep joints. Keep your finger damp and keep smoothing until you have a seal without gaps or indentations.