Caulking 101: What, When and How to Seal the Deal With Caulk

By thewriteDuffy •  Updated: 06/07/24 •  5 min read

We all want a “tight” house with no drafts or leaks so we save money on energy bills and keep out moisture to avoid water damage and mold. We also want our water-laden areas — the kitchen and bathroom — to keep water where it belongs.

The Different Types of Caulk and When to Use Them

Three Varieties of Caulk: Tub and Tile; Paintable Acrylic Blend Window, Door and Molding; and Silicone Window, Door and Molding.

1. Tub and Tile Caulk

For bathrooms, you’ll need caulk labeled for tub and tile. These are formulated for high-moisture areas and resist mold and mildew.

Within this type of caulk are several variations, including sanded ceramic-tile caulk, which is available in colors to match the color of your grout so you’re not limited to bright white or clear caulk.

2. Trim and Molding Caulk

Caulk for use around doors, windows, and molding will be clearly marked. Generally, the same caulk can be used for all of these applications.

Make sure that the product you get is labeled as paintable because paint will not adhere properly to certain types of caulk — it will bead up like oil trying to mix with water.

3. Exterior Use Caulk

For outdoor applications, select caulk that’s rated for exterior use. Most often these will be either silicone-based or an acrylic blend with silicone added.

How Large of a Gap Can You Fill with Caulk?

Although it can be tempting, caulk shouldn’t be used as a filler. For gaps larger than 1/4 inch, you’ll need to use a spray foam or backer rod to fill larger gaps, and then follow up with caulk. Backer rod is usually found with weather stripping.

How To Use a Tube of Caulking

A Typical Caulking Gun.

Most caulk comes in a tube that requires a caulk gun, which consists of a “trigger” that drives a plunger pushing the caulk through the tube toward the tip.

Caulk guns are a must-have and range from just a few dollars to $12 or more. They all perform the same function, so there’s no point in buying the most-expensive caulk gun unless you’re a pro.

Your best bet is a midrange gun at about $6. Some of the cheaper ones — less than $3 — can stick and have to be taken apart and reassembled frequently, which is not something you want to do in the middle of a job.

Applying Caulk

Start by removing or cutting off the tip of the calk cartridge. The opening at the tip determines the size of the caulk bead so start small and go bigger if you must.

Insert a metal pin into the tip of the cartridge and remove it. Often your caulking gun with have a metal pin in the handle to use.

Pull back the caulking gun’s plunger or rod and load the cartridge into it.

To dispense the sealant, apply even pressure to the trigger. When you release the trigger, calking will continue to dispense due to a buildup of pressure.

You will have to push the catch plate to make it stop. This is something I didn’t know my first time using one, and a giant mess was the result, so don’t forget this step.

Caulk Being Smoothed out By Hand.

After you’ve applied a bead of caulk by pressing down on the caulking gun trigger and running it over your gap to put a bead of caulking over it, simply use your finger followed by a damp paper towel to smooth it out.

If that’s a bit messy for your liking, many spreading tools are available.

You can also use painter’s tape to give you a professional edge once the caulk has been smoothed and pressed into the gap.

Caulk Being Applied to A Sink Using Painter’s Tape to Create a Clean Edge.

It should be noted here that caulking guns are also used for tubes of adhesives and glues, which we cover in this post about adhesives, glues, and epoxies.

Do You Need a Caulking Gun to Use Caulk?

Caulk manufacturers also make smaller tubes of caulk that don’t require a caulk gun. They’re a lot like a tube of toothpaste.

Many of these come with tips that can be screwed on and removed, which makes cleaning much easier.

How to Re-Seal a Tube of Caulking: Caulking Caps

Tube of Caulk with a Wire Connector as a Makeshift Cap.

Once you’re done your caulking for the day, if you need to store a half-used tube you’ll want to cover the tip in some way to prevent the tube from drying out.

Some tubes of caulk will come with a cap. If not, a great trick for capping an open tube of caulk is screwing a wire connector onto the tip. Connectors are threaded so they will grab onto the tip and stay in place.

If you have the right size, you can also insert a nail into the nozzle to prevent clogging and seal it up.

Conclusion: Seal Gaps and Get a Nice Finish With Caulking

Whether it’s windows, bathtubs, sinks, doorways, or trim, caulking can close the gap and give you a nice, clean and leakproof seal.

However, caulking isn’t for every job. If you’re looking to seal two materials together, it’s likely that you need a glue, adhesive, or resin. If you’re filling a dent, nail hole, or other gash in your trim or door or wall, a wood filler or drywall compound is usually best. Click the links for more information.


At home, April is a mom, wife, and DIY darling. Among other home projects, she helped her husband Dan renovate their 1986 bungalow and is currently designing and decorating the 2023 custom home they are building themselves. Professionally, April is a writer, author, and online marketer with 15 years of experience writing for newspapers and magazines, building online authority websites, and publishing books.