How To Caulk a Bathtub or Shower
The caulk around the seams of your bath tub or shower serves a very important purpose. While it provides a decorative transition between surfaces, more importantly, it keeps the bathing area water tight. Water that gets past seams and into walls leads to loose tiles, wood rot and mold. Each of which can be very costly to repair.
If the caulk around your tub or shower has come loose or is discolored or mildewed, it should be replaced. While you could patch just the affected areas, caulk does not stick to dried caulk very well. The repair will tend to leak and to come loose after a relatively short time. The best practice to completely remove all the old caulk, clean the surfaces and put down fresh caulk.
How To Remove Old Caulking
There are two common types of bathroom caulk, silicone and acrylic. There are also hybrid siliconized-acrylic and latex caulks. Silicone caulk tends to be rubbery, acrylic and latex are more rigid.
When removing silicone caulk, it is imperative that you get all of the old caulk out and all remnants cleaned from all surfaces. Silicone caulk will not stick to old silicone caulk and thus any new caulk will ultimately leak and fail more quickly. Start by using a single-edged razor blade in a blade holder or a utility knife to slice through the old silicone caulk to separate it from all adhered surfaces. Pull out as much of the caulk in pieces as possible. Next, use the razor at a low angle to shave off remaining caulk. Be careful not to scratch the tub. If the razor leaves black marks on the surface, alcohol or mild cleansers should remove them.
Removing acrylic and latex caulks is similar to removing silicone although it is less likely to come out in strips. Scrape out as much caulk as possible. If the caulk is particularly difficult, try warming the caulk with a hair dryer or heat gun. Warm it enough to make it more flexible then scrape it with a razor or utility knife.
Finally, clean the area thoroughly with a wipe down using rubbing alcohol. The alcohol tends to break down any small remnants as well as effectively dissolving soap scum and other materials adhering to the surfaces of the tub, tile and enclosure. It is also necessary to make a second pass with a chlorine bleach solution to kill all bacteria, mold and mildew. Alcohol alone will not kill all forms of bacteria and mold.
Before applying new caulk, all surfaces must be completely dry. If pieces of the old caulk were coming out, it is likely water got behind the caulk and into the interior surfaces. If you recaulk over this moisture, you risk continued damage as well as a shorter life span for new caulk. Wait overnight, or even run a fan over the area to accelerate evaporation.
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