What's your Caulk IQ?
Fifteen questions on technique, chemistry and a surprising amount of maritime history. Every answer comes with the why.
Zoe wrote the questions.She'd like you to know that joint movement is not a dance.
Question 1 of 15
Score: 0
1Before you squeeze, how should you cut the tube's nozzle?
An angled cut lets you hold the gun at an angle and push the bead into the joint instead of smearing it on top. Start near the tip with a small opening. You can always cut more, never less.
Learn more: How to lay a perfect bead
2You're sealing around a shower. Which formulation is the right call?
Showers are constant-wet zones, and 100% silicone is the gold standard there: waterproof and very flexible. Just remember it won't take paint.
Learn more: 100% silicone, explained
3You plan to paint the trim right after caulking. Which caulk should you skip?
Paint beads up and peels on standard silicone. Acrylic, siliconized acrylic and elastomeric latex all take paint.
Learn more: Formulations at a glance
4What's the main job of backer rod?
Backer rod fills deep gaps so you use less sealant, gives the bead the right shape, and stops it from bonding to the bottom of the joint.
Learn more: Backer rod and joint design
5Why is “three-sided adhesion” bad news for a moving joint?
A joint that moves needs sealant bonded to two opposite faces only. Stuck to the back too, it can't stretch evenly and rips. Backer rod or bond-breaker tape prevents it.
Learn more: Backer rod and joint design
6What does “tooling” a bead mean?
Tooling presses the sealant into full contact with both sides and leaves a neat, slightly concave surface. Do it right away, before the caulk starts to skin over.
Learn more: How to lay a perfect bead
7What does a “dripless” caulk gun do?
Leftover pressure is what makes caulk keep oozing after you stop. A dripless gun releases it automatically when you let go of the trigger, so you get fewer blobs and less waste.
Learn more: How to lay a perfect bead
8Water is actively trickling through a crack in your basement wall. What goes in first?
Hydraulic cement sets in minutes, even with water flowing. It's rigid, though, so it's an emergency plug, not a joint sealant. Once it's dry, seal cracks that move with a flexible product.
Learn more: Hydraulic cement, explained
9Grout or caulk: what belongs where a tiled wall meets the tub?
Grout is rigid and made for tile-to-tile joints. Where materials change or planes meet, like tile to tub or inside corners, things move, so you want a flexible sealant there.
Learn more: Caulk vs. sealant vs. grout
10Why does bathroom caulk so often turn black?
Moisture plus soap scum is a feast for mold. Surface mildew can sometimes be cleaned off, but when it's growing underneath, the real fix is to remove the caulk, clean and dry the joint, and re-seal.
Learn more: Removing old caulk
11You're about to strip old caulk from a building built or renovated between 1950 and 1979. What should you think about first?
The U.S. EPA has warned that some caulk used in buildings from that era contains PCBs, and some older sealants and glazing compounds contained asbestos. If you're not sure, have it tested before you scrape or sand.
Learn more: Removing old caulk
12Where does the word “caulk” come from?
It came into English through Old North French cauquer, “to press,” from Latin calcare, “to tread,” which itself comes from calx, “heel.” Pressing stuff into seams is the whole job.
Learn more: A sticky history of caulk
13Before modern sealants, what did shipwrights hammer into the seams between a wooden hull's planks?
Caulkers drove oakum into the seams with a caulking iron and mallet, then sealed over it with hot pitch.
Learn more: A sticky history of caulk
14What size is the standard caulk cartridge in the U.S.?
The 10.1-fluid-ounce cartridge (about 300 mL) is the size nearly every standard caulk gun is built for. Bigger sausage packs and jumbo cartridges exist for pros and big jobs.
Learn more: How many tubes do you need?
15Many latex caulk labels say to apply it when it's at least how warm?
Around 40°F and rising is a common minimum for latex caulk, with no rain or freezing until it cures. Some formulas are rated for colder weather, so check your tube.
Learn more: Caulk FAQ
More ways to play
Brains warmed up? Put them to work.
Bead Master
Knowing the theory is one thing. Lay a smooth, steady bead without blobs or gaps.
Play Bead Master PuzzleThe caulk crossword
Two grids, Apprentice and Master, packed with sealant vocabulary and a few shameless puns.
Solve the crossword QuizWhich caulk are you?
Nine questions to find your formulation. Are you flexible, paintable, or just very, very clingy?
Find your caulk