Last edited 29 Nov 2022

Caulk

Caulk is filler material commonly used by decorators. Most caulks are more rigid than sealants, but more flexible than other fillers when they dry and can be used where movement or leakage can occur - as long as significant expansion or contraction is not anticipated.

Historically, caulk was made from fibrous materials that could be driven between boards, pipes and so on to make them waterproof. Rope caulks are still available and are primarily used to reduce drafts, and sound transmission, especially around windows.

Modern caulk is also waterproof. It is typically made from acrylics, vinyl or silicone. These materials dry quickly and remain relatively flexible. It can be used to close small gaps and crevices. It prevents air, insects, rodents and dust from compromising the integrity of seals, spaces and structures.

Acrylic caulk can be painted after it has dried completely. However, painted caulk can crack if it is applied in temperatures lower than four degrees Celsius. Silicone caulk cannot be painted.

Caulk is generally sold in cartridges that can be inserted into caulking guns. This technique helps to control the application process. If spills and smears occur during the process, they can be cleaned up with water rather than solvents.

It is possible to caulk over old acrylic caulk, unless the old caulk is oily, dirty or has deteriorated significantly (in which case, the new caulk will not adhere). Caulk should not be applied over old caulk that is wet or has mould or mildew.