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Caulking: A Little Is Enough

29 September, 2020

Caulking application is one of those necessary skills that experienced painters sometimes take for granted. You just do it, and you do it right. You expect that it should be that easy for everyone, but often it isn’t. 

I haven’t seen many newbies come along with a natural aptitude for caulking, so we have to remember to train for this prep skill in our companies. It is a skill that every painter needs to master.

My company didn’t spread a lot of caulk this season, and I consider that a good thing. We have done quite a fair amount of both interior and exterior painting this year, and I found that we used more caulking on interior trim than on exterior surfaces. I don’t mean for that to sound like criticism of the interior carpenters we work with; they are really quite good — but whether in interior or exterior applications, using just the right amount of caulking for the situation is the important goal to train painters to achieve.

It's not sandable!

One of the most common reasons for paint (and caulking) failure that I have observed over the years is users applying too much caulk, then painting over it before it is dry. This is a failure that my company has had to fix many times over the years, and there aren’t many tasks less fun than scoring, blading and scraping out failed caulking that was put on too heavily.

So pass the word along to your painters — and even your DIY neighbors — that using more caulking than needed is actually a bad idea. Caulking is intended to go in gaps and cracks, not on surfaces. It is done best when you can’t see it, kind of like auto body cosmetic work. As soon as you can see that something has been caulked, it is going the wrong way. The more that is left out on the surface, the better the chance for failure, and there is nothing that will cause overapplied caulking to crack and start to fail more than wet paint before the caulking is dry.

To experienced painters, this is all Paint Academy 101, but it is amazing how much it happens. I think it is a reflection on the reality that people don’t want to spend much time painting, and they want to spend even less time on prep. They want to get the caulking on fast and get to the paint as quick as possible.

This speculation is consistent with my long-standing theory that painters (or regular people) who want to be done with the process fast tend to apply way more product than is typically needed or recommended. I have written about it in the past, how it is easier to spread paint heavier when moving faster. Spraying would be the one exception. Fast spraying usually makes the coat thinner, so you end up needing to do multiple stacked coats, which can also lead to adhesion issues and failure. But for those mechanical applicators — brushes and rollers — loading them up super full and spreading fast is always tempting to those not wanting to spend much time on the project.

What about not painting it all?

The caulking is white, the surfaces are white, who will ever notice? Ahh, the temptation to skip a step to get done faster. This is a case where immediate gratification is beat by long-term concerns. If you don’t paint caulking, it discolors and collects organic matter easily. It’s not a pleasing outcome at all; in fact, it creates a really dingy look in a short amount of time. Corners, joints, edges and gaps need to be clean and crisp. Our eyes, and our customers’ eyes, follow lines around a room. Cut lines. Caulk needs to disappear in the cuts.

So train painters to the discipline of applying the proper amount and letting it dry completely — the less you put on, the faster it dries — then paint to make
it disappear.

For your training manual

Here is a page to add to your company playbook that would apply pretty uniformly to both interior and exterior caulk prep scenarios:

There is always some debate on the proper time to caulk, but it is usually best to caulk after the primer and before the finish coats. If you caulk over bare
wood (before priming), the wood can suck the moisture out of the caulk and cause it to crack. On the other hand, you want to bury the caulk in as many coats
of paint as possible, which is why the best time to caulk is after the prime coat and before paint coats. Make sure all filling and cosmetic work has been done, then lightly sand and clean the surface. Dust bunnies do not mix well with caulking.

High-quality acrylic latex caulks are easy to use, so choose a good allpurpose acrylic latex plus silicone — it is possible to find one product that works well on both interior and exterior applications. Always let the caulking dry completely before painting over it. Painting over uncured caulk is a sure-fire recipe for cracked caulk.

Keep a damp rag and small pail of water handy when caulking. This makes it easy to keep your fingers clean for spreading caulk. It’s hard to finger a nice line if there is dry and caked product on your fingers. Snip the nozzle on the tube to open a tiny hole in the tip (less than 1/8-inch diameter). As with applying paint, try to work from the top down. Begin with a bead of caulk along the top edge of trim and wipe the joint to wall immediately with a wet finger or tight
rag, removing much of the caulk that was applied. From there, wrap the damp cloth around your finger and go back over the joint a couple of times. Each pass cleans the wall and the surface of the trim a bit more until all the excess residue is gone. When satisfied with the caulked joint, rinse the rag thoroughly in clean water before going to the next application.

Use a 5-in-1 tool to clean up inside corners where the two lines of caulking meet. Apply beads of caulk and wipe the majority of the line with your smallest
finger. Use the square corner on the blade of your 5-in-1 tool as a miniature putty knife to tool the bead neatly along the profile of moldings and joints. Use
the sharp point to clean tight corners and narrow grooves. When all the joints have been caulked, inspect every surface carefully with a work light. When white
caulk is used over white primer, small ridges of residue might not show up until you look at it in good light to search for edge shadowing.

Remember: A little goes a long way!

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