Caulk is important. It’s the easiest marker of a bad DIY job – they skipped the caulk.
But what if you did everything right, finished the job with caulk… but that caulk won’t dry?
The most common reason caulk doesn’t dry properly is because there is too much moisture in the air. Temperature and application thickness can also affect dry times. If after a week the caulk has not dried, remove the caulk and reapply with a new tube.
But there are other reasons your caulk might still be soft, so keep reading!
Note: This blog contains affiliate links. If you click and make a purchase, I may receive compensation (at no additional cost to you.)
Reason 1: Heat and Humidity
The condition of the air when you apply the caulk significantly affects dry times.
If the air is humid, whether naturally or because the caulk happens to be in a frequently used bathroom, it will dry more slowly than in a room with less moisture.
Additionally, latex-based caulk is temperature sensitive during application. DAP’s Alex Plus caulk recommends applying the caulk between temperatures of 40 degrees Fahrenheit and 100 degrees Fahrenheit, although after drying, it works in a much larger temperature range.
(This makes sense when you consider that latex caulk is water-based, and therefore subject to freezing when still wet. Latex paint is too, which I learned in this fun experiment.)
Silicone caulk isn’t water based, and therefore has a much larger temperature range.
This DAP Silicone Caulk allows for application down at -35 F. As someone who lives in Minnesota, I would love to know exactly who is out there applying caulk on our -35 degree days, because FYI, I am not.
If you suspect your caulk isn’t drying because of temperature or humidity, the answer is fairly straightforward: fix the conditions, and your caulk should dry properly.
Hopefully you’re working indoors, and have the ability to either turn out the heat or the AC.
But if not, in many cases, waiting a week or so should provide enough time for the caulk to dry, even if it takes much longer than normal.
If, even after a week, your caulk still hasn’t dried, there are two possibilities.
One, your weather is too extreme, in which case, remove the caulk and try again next season.
Or two, one of the other causes is at play, so keep reading.
Reason 2: The Caulk Is Too Thick
When I fill gaps and holes, I usually have three options to choose from: caulk, epoxy resin, and wood filler.
I don’t always choose the right one.
There were a ton of holes that needed to be filled on these DIY countertops:
I started with epoxy, but it was too thin, and just flooded the space underneath the boards when the holes went all the way through.
So then I switched to caulk, and filled the holes all the way up to the top, leveling them off with my finger when I was done.
The caulk didn’t flood out the bottom (yay,) but this hole took literal weeks to dry. Sometimes I still think I can see some undried white caulk in there.
(See how white and foggy it is? There’s got to be undried caulk in there.)
Moral of this: caulk isn’t intended to fill large gaps. Anything larger than 1/2″ by 1/2″, and you should choose a different medium.
In the case of my countertops, the correct answer was to seal the bottom with caulk, then fill to the surface with epoxy. I topped off the caulk holes with resin, then put this fully into practice on the island portion:
Side Note: If you’re wondering why I don’t have any in-progress pictures of this, it’s because I chopped my thumb off in the middle of this project. True story, you can hear all about it over on Youtube.
Six months later, when my thumb was healed enough for me to finish it, I just wanted it over with.
You’ve got a couple options here. First off, if you’re patient, that caulk will probably dry eventually.
So choice one: wait it out.
Choice two depends on exactly where your caulk is. If you’re looking at caulk that’s surrounded on 3 of 4 sides, it might be challenging to dig it out, so choice one might be your better bet.
But if this is caulk that’s mostly accessible, you can always remove it with a putty knife and start over.
Reason 3: The Caulk Has Gone Bad
Unopened caulk has a shelf life of 1 year, while opened caulk has a shelf life of 2 months.
That’s not to say it can’t last longer, but that’s what the manufacturer recommends.
Now, I’ve used caulk that’s much older than that. I just stick a screw in the end of the tube, and pull it out again next time I need caulk.
But the key to this trick is to test your caulk before plopping it on your project.
Put it on some scrap wood, and see if it dries. If so, you’re good. If not, toss the caulk, and go buy a fresh tube.
Side Note: I keep linking to DAP, because DAP is the manufacturer that has all this information easily findable online. This is not sponsored, and while I’ve used and liked DAP, I haven’t found their caulk to ultra-special-magic.
I do appreciate that they publish their product information, though.
If you don’t think heat, humidity, or thickness are the reason your caulk won’t dry, and you’ve waited a week and your caulk is still soft, this is probably the reason.
In that case, there’s no saving this caulk. Take it off with a putty knife, and start over.
Reason 4: You’re Using the Wrong Caulk
Caulk is formulated for the surface it’s bonding too.
If you’re working in a bathroom, you should be using tub and tile caulk. Windows and doors? Window and door caulk. Wood countertops? All-purpose caulk.
Using the wrong caulk causes multiple issues, the main one being adhesion. But it also prevents the caulk from drying correctly.
Take the caulk off with a putty knife, and go get the right caulk.
Reason 5: The Caulk Got Wet
This is mostly true for latex caulk, but if latex caulk gets wet, it will slow down the drying process.
This same thing is true for paint, if you were wondering (and in that case, is useful for preventing brushstrokes.)
Now, if you’ve been waiting weeks, this probably isn’t why your caulk won’t dry.
But if it’s just been a few hours, and you’re wondering why your caulk isn’t dry yet, this might be the reason.
Wait another 24 hours. If the caulk still won’t dry, start thinking about the other reasons above.