Introduction: All About Caulk and Caulking

About: I love woodworking and tinkering and make new videos about it every week! Come join me on my YouTube channel!

Just letting you know that this article has affiliate links in it that hopefully will help me pay the bills and keep writing more! If you want to help me out just click here and buy whatever you were going to buy anyway. I really appreciate it! :)


Let's have a Caulk Talk.

Modern caulk is most commonly made of silicone or acrylic. You can also find caulks which are polyurethaneor polysulfide.Each of these caulks are used for very different purposes as they have very different properties.

My favorite caulking tools:

  1. This amazing caulk gun. Pay more for a quality caulk gun and your hands will thank you.
  2. 3M caulk remover liquid
  3. A caulk tool for clean edges and a more professional look
  4. A paint scraper hook tool
  5. A good scraper tool

Step 1: What Is Caulk Used For?

Caulk is used to infill gaps, to seal, and to glue.

There are specific caulk types for bathrooms, kitchens, concrete, gutters, moulding, roof, windows, plumbing, interior and exterior jobs, and more.

Silicone and polyurethane caulks are commonly used to seal in a wet environment as they don't degrade when exposed to water, are flexible, and can create a perfect seal. You'll find it commonly used around bathtubs, toilets, sinks, and to seal around windows.

Acrylic Caulk is commonly used to fill gaps in moulding around rooms, doors, and windows. It dries hard and isn't flexible, and can be painted over without worrying about it cracking.

Polysulfide Caulks are designed for joints that need to withstand prolonged immersion in liquids. Typical applications include swimming pools, fountains, cooling towers, fuel and chemical storage tanks, wastewater treatment and petrochemical plants.

Step 2: How Was Caulk Used and Made in the Past?

Caulking (or calking) was commonly used in history and prehistory as a way to make seams in wooden ships water tight. The vikings used a method called Clinker (or lapstrake), which was overlapping boards clinched together and then riveted together by brass or iron rivets. The more relevant method (for our caulking discussion) for making ships watertight is called Carvel construction.

In Carvel construction, caulking involved using a scraper and hook to clean out the seam between the planks and then using a caulking mallet and caulking irons to pound and compress caulking into the seam. The caulking used was usually "oakum" which was tarred hemp cordage material.

Here is a really neat video of this process.

After caulking, the seams would be covered with hot pitch. Below the water line the caulked seams would be filled with paint. Above the water line white lead was commonly used. This was known as "paying" the hull.

Caulking did not last forever and hulls would need to have caulking repaired, or be re-caulked at intervals.

None of these wooden shipbuilding techniques was perfect at keeping all water out. Ships took on water especially when being twisted or "worked" by severe weather. Pumps, or bailers in the case of the Vikings, were employed to get unwanted water out of the hull.

Step 3: How Is Caulk Made?

Caulks are all made from one of four base compounds: acrylic latex, silicone, polyurethane or rubber. The base compound determines specific characteristics, such as what materials it will adhere to, how easily joints can be smoothed, durability, paintability, etc.

Latex and acrylic caulks are water-based and made up of synthetic polymers that resemble natural latex—but there is no actual latex in them. They are an umbrella term, and within this category of synthetic water-based paints are a variety of specific types.

Silicone rubber is an elastomer (rubber-like material) composed of silicone—itself a polymer—containing silicon together with carbon, hydrogen, and oxygen. Silicone rubbers are widely used in industry, and there are multiple formulations.

Polyurethanes are formed by reacting a polyol (an alcohol with more than two reactive hydroxyl groups per molecule) with a diisocyanate or a polymeric isocyanate in the presence of suitable catalysts and additives.

Polysulfides are a class of chemical compounds containing chains of sulfur atoms. Many commercial elastomers contain polysulfides as crosslinks. Polysulfide caulks should not be used on plastics as they will degrade the plastic they are attached to.

Image is from this neat but short tour of a sealant factory in china:

Step 4: Can You Make Your Own Caulk?

Yes, you can make your own home-made caulk.

A mixture of baking soda and wood glue will work in a pinch. Mix 2 tablespoons of baking soda with enough glue to create a thick mixture. You won't have access to a tube dispenser to cleanly apply your DIY caulk. I've had mixed success with things like cut straws, Popsicle sticks, and a small spoon. This caulk will work OK in instances when you need to close a gap, as when you are painting moulding or similar types of touch-ups. It isn't a good long-term fix and you'll have to eventually pull it out when it moves or cracks with time. Modern caulks are so common, cheap, and available there is really no real reason to make your own.

Step 5: What Is the Best Way to Caulk?

No matter what job you're doing or which type of caulk you are using, the process for applying caulk is mostly the same.

  1. Make sure the area you are caulking is clean of oils and dust. Wipe it down and make sure it is totally dry. Caulk will not adhere evenly to a wet area and you will end up having to remove the caulk and do it again. Take the time to prep your area properly!
  2. Place your caulk tube into your gun by releasing the tab and pulling the hook back. The tube should fit firmly. Push the hook down until it bottoms out. Don't squeeze yet!
  3. Grab your utility knife and slice open the nub, being careful not to cut off the threads. You'll need those threads to attach your nozzle!
  4. Get your tube nozzle and screw it on. Use your utility knife again to cut the tip off. The smaller your hole, the more economical your application will be, and that is a good thing.
  5. Set the tip of your gun in the corner of the area you want to fill. Gently squeeze the trigger of the gun until a small bead of caulk comes out.
  6. Don't use too much! A little bit goes a long way. Move slowly along your gap and squeeze gently on your gun's trigger until you reach the end of your joint.
  7. Take your caulking tool and run it over the joint to clean up your bead. If you have any gaps, carefully fill them and re-run your caulking tool over the joint.

Make sure to set your caulking gun down on to a paper towel or rag. Cap your nozzle when you are done so that the caulk doesn't harden and clog your tube.

Step 6: How to Remove Caulk

Removing old caulk can be a painful experience, but it doesn't have to be! Take your time, use the right tools, and try to stay focused and eventually you'll get there.

  1. Start with some quality caulk remover before you start with mechanical removal. Apply and wait as long as you can. The instructions say to wait two to three hours, but with old caulk you should wait longer. Overnight is best if you can.
  2. I highly recommend getting one of these tools. Use the tool to slice along the top and bottom rim of the caulk.
  3. Use the hook to grab underneath the strip of caulk and pull it out. If you are lucky it will all come up in one satisfying strip. For old caulk it is likely to break and come out in chunks. Get out what you can and then carefully use a clean scraper tool to get the rest of the caulk off.
  4. For tile, clean off the area you're going to re-caulk with mineral spirits. For wood, you should wipe it clean with water. Wipe dry with a clean cloth.