Caulk, Sealants and Threadlockers

Silicone, acrylic latex or polyurethane: the surface decides

Silicone stays flexible and waterproof, bonds well to glass, tile and metal, and is the usual choice for tubs, sinks and windows, but most types cannot be painted. Acrylic latex caulk is paintable, cleans up with water and suits interior trim and gaps. Polyurethane and hybrid sealants adhere strongly and tolerate movement outdoors. Read the label for the surfaces it bonds to, the temperature range and whether the cured joint can be painted.

Specialty compounds work differently. Gasket makers form a seal between machined flanges and are chosen for the fluid and temperature they must resist. Putties and filler compounds repair holes and cracks, while liquid rubber and asphalt-based products seal roofs and foundations. Tintable and color-matched caulks come in white, clear, gray and black, so choose a color by where the joint sits and how visible it will be.

Cartridge size, cure time and threadlocker strength

Standard caulk guns take a cartridge of about 10 fluid ounces, and a single cartridge fills roughly 20 to 25 feet of a quarter-inch bead. Multi-packs are common for larger jobs, so compare the quantity in each listing. Deep joints need a backer rod behind the sealant, and cure time is different from the shorter skin-over time: avoid water, painting or strain until the label says it has cured.

Threadlockers are a separate product. They are liquids that fill the gap between mating threads and harden to stop vibration loosening. Strength is the choice: low and medium grades can be undone with hand tools, while high-strength grades need heat to release. Many brands use a color code, often blue for medium and red for high, but read the label because it is not universal, and check the product is safe for plastic parts.

Questions about Caulk, Sealants and Threadlockers

Can I paint over silicone caulk?

Usually not. Paint beads up or peels off cured silicone because nothing sticks to it. If the joint must be painted, use acrylic latex or a sealant labeled paintable, and let it cure before painting. Some hybrid sealants are made to take paint, but the label has to say so.

Can I put new caulk over old caulk?

Not reliably. New sealant bonds poorly to old, so cut out the old bead, scrape the joint, clean it of soap scum and oil with a solvent such as isopropyl alcohol, and let it dry. Fresh caulk then bonds to the surface itself and lasts longer, particularly in wet areas.

Which gasket maker suits a flange seal?

Pick by what the joint sees: oil, coolant, fuel or high heat. The label lists compatible fluids and a temperature range, and some products set quickly while others stay flexible. A formed gasket may still be required for large gaps, so check the equipment's service instructions.