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A Guide to Caulk
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Over time, building structure material expands and contracts -- particularly wood. To keep the structure in its correct form, a caulk application will waterproof, insulate and seal. Caulk sticks, stretches and then recovers the original shape of the structure, flexing with the material as it ages. September is a great month to weatherproof for the upcoming stormy season. All caulking jobs need to be finished before you begin a painting project.
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| Acrylic Caulk |
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| Silicone Caulk |
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| Siliconized Acrylic Caulk |
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| Applying Caulk |
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When choosing caulk, consider: the type of material(s) you want the caulk to adhere to, if there will be residual moisture on the surface of materials during application, if the caulked joint will be subject to moisture, water or weather over time, what temperatures the caulk needs to withstand, if the area is subject to frequent temperature fluctuations, if the area is vulnerable to mildew growth, and if you wish to paint over the caulked joint.
Silicone Caulk
Silicone caulk is excellent for smooth, nonporous surfaces, such as metal, glass, glazed tile and plastics. It does not work as well with porous materials such as concrete, masonry and wood. 100%, neutral-cure silicone works best. Although pure silicone cannot be painted, it is available in pigmented form.
Acrylic Latex
Acrylic latex caulk is a general-purpose sealant. It adheres best to porous materials like wood and concrete. It will adhere to nonporous surfaces as well but not as well as silicone caulk. It can be painted, but is also available in pigmented form.
Siliconized Acrylic Latex
Siliconized acrylic latex caulk is also known as “all-purpose” caulk. It is good for both interior and exterior applications, and is long-lasting.
Specialty Caulks
Specialty caulks tend to be more difficult to apply and clean up. However, they can’t be beat for specific applications. For example: Polyurethane caulk is excellent for marine use.
To Apply Caulk
Make sure the area to be caulked is as dry as possible, free of grease and free of old caulk. The caulk should not be allowed to stick to the material at the back of the crack (otherwise it won’t flex as the gap changes).
Insert the caulking cartridge into a caulking gun shell. Cut the cartridge’s plastic nozzle at a 45° angle. Poke the pointed end of a large nail into the cartridge nozzle, breaking the seal.
To operate the caulking gun, pull the trigger to squeeze caulk into the crack you are filling. Hold the caulking gun at a 45° angle, pull the trigger and, at the same time, pull the gun down the crack. Take your time and move with a steady motion. When you have finished running a bead of caulk, immediately turn the plunger at the back of the caulking gun, so caulk doesn’t continue to ooze out of the nozzle.
The ideal caulk joint sticks to materials on either side of the gap, and is only about half as deep as the gap it spans. Apply caulk carefully where water penetration can cause a lot of damage.
Remember to be sure you clean up stray caulk as soon as you finish your project.
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- Hardware Hotline September, 2008
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