First, you probably know that there are several different types of silicone that differ in their curing chemistry and the byproducts they emit (i.e., the odor as they cure). The oldest are the acetoxy sealants that give off acetic acid (known as a vinegar smell). More modern sealants, such as oxime or alkoxy silicones, release a musty or mild alcohol smell.

I consistently find that the acetoxy silicones give the best adhesion, although they smell the worst. You may also notice mildew and staining on silicones caulks as they age in a moist environment. This, unfortunately, is inevitable; cleaning and drying the joints will slow it down. A major silicone manufacturer once told me that it is possible to make a caulk that is totally resistant to mildew formation, but the mildewcide/fungicide is far too toxic to incorporate in a consumer product.

Many people also have a problem with tooling the silicone after application. Several tools are available, but a wet finger is still the best for me. The real secret is to apply a much narrower bead of product than you think is needed.

Silicones will last longest of all sealants in an outdoor environment, although lack of paintability is a disadvantage. The main alternatives to silicones are acrylic latex caulks. They don’t have the durability or flexibility of silicones, but acrylic latex caulks are somewhat easier to tool, easily clean up with water, and can be painted readily. ASI

Any views or opinions expressed in this column are those of the author and do not represent those of ASI, its staff, Editorial Advisory Board or BNP Media.