DEAR TIM: The caulking in several places in my bathroom has mildewed. I have tried unsuccessfully to stop the mildew growth. I want to install new caulking. How do you easily remove caulking? What kind of caulk can I install that will not support the growth of mildew? Andrea Z., Hobe Sound, FL
DEAR ANDREA: Welcome to the club! Many homeowners, including myself, have battled unsightly caulk joints in bathrooms, kitchens and other high moisture locations for years. I have good news and a little bad news. You can now purchase mildew proof caulks to eliminate future mildewed caulk problems. The bad news is that it is going to take some effort on your part to remove the existing caulk. To the best of my knowledge, there are no miracle caulk removers.
Bathrooms, and kitchens are ideal locations for mildew growth. Mildew needs a moist environment and food to thrive and survive. Bathrooms - especially tub and shower areas - provide ideal growth conditions for mildew. Daily showers and baths supply water that often ponds at the locations where you frequently use caulk. These areas are often the last to dry out as the water evaporates. Body oils, soap films, shampoos, and other hair care products almost always contain ingredients that provide mildew spores a continuous, delectable smörgåsbord. Certain caulks actually contain organic ingredients that mildew eat.
Caulk removal begins by manually scrapping out the bulk of the old caulk. You can use a razor blade or any other type of cutting or scraping tool that will not hurt you or the materials adjacent or beneath the caulk. If you decide to use a razor knife of any type, I suggest you wear medium duty leather gloves to protect your hands during the removal process. Feel free to incorporate some water as a lubricant. The water will help to minimize scratches to tile or plumbing fixtures. Work slowly and carefully. Remember, the more power you exert while scraping or cutting, the more control you lose over the scrapping tool.
Once you have removed the bulk of the old caulk, you can try several off the shelf caulk removers or products you may already have in your own home. Experiment first with plain water. If the original caulk was a non-acrylic water based caulk, soaking it with water saturated rags for 3 days can soften the caulk remnants. Water based acrylic caulks and those made with polyvinyl acetate resins can often be softened by soaking them with isopropyl rubbing alcohol. The alcohol swells the old caulk molecules and helps to lift them from the surrounding materials. Be careful when using the alcohol as it is a flammable substance and often burns with little or no flame.
Silicone caulks are the hardest caulk to remove. There are not really any solvents you can buy to easily remove silicone caulk. Multiple applications of strong alkaline compounds like sodium or potassium hydroxide can soften silicone caulk. However, these chemical compounds are dangerous and can often burn you or the materials surrounding the caulk. You can try oven cleaners or strong powdered cleansers that you mix with water to a paste consistency. Apply these carefully to the caulk with a cotton swab. These compounds can dull plastic laminate tops, acrylic and fiberglass tub and shower units and many other bath and kitchen materials. You must work slowly and carefully.
Once the old caulk is removed, purchase new mildew proof caulks that are widely available. These caulks often contain vast quantities of mildewcides - chemicals that leach from the caulk over time and poison the mildew spores. Some of the caulks come in beautiful colors and offer lifetime guarantees against mildew growth.
You can minimize mildew growth in bath and shower areas by cleaning them on a frequent basis. Cleaning and rinsing all surfaces with clear water will remove mildew food sources. You should also keep tub and shower doors and curtains open after you leave a bathroom. Leave bath doors open as well to speed the drying process.