If you’ve ever painted a wall or anything else with runny paint, then you know the frustration involved. Nothing’s worse than scanning over an area that you have already painted, and noticing dozens of runs in your paint!
Now, you have to take your roller or brush and smooth out those runs, which not only eats up your time and energy, but also, most likely, creates a subpar finish to your paint job.
But what can you do about thin, runny paint? You certainly don’t want to continue trying to complete your painting project with paint that runs faster than an Olympian!
Can you thicken paint? Yes!
And I’m going to show you various effective and affordable ways to do it in this article. You can use these simple tricks to thicken your paint, stop it from running, and create beautiful results.
Let’s not waste time. Let’s get right into how to thicken paint so that it does not run.
Here we go!
Anatomy of Paint
Before we dive into how to thicken paint, let’s quickly go over the anatomy of paint, so that we understand better what’s happening when we thicken it.
All types of paint are made up of 4 primary ingredient types:
Each of these components of paint contributes to the paint’s characteristics, including its viscosity (thickness). Let’s look quickly at each.
Pigments determine the color of a paint. Most pigments are dry powders, which must be combined with binders and solvents before they can be mixed in liquid to create spreadable paint.
Binders determine a paint’s adhesion rate, washability, and resistance to fading. They bond pigment molecules together, and also allow the paint to stick to the surface being painted after the solvent evaporates.
Solvents are chemicals that dissolve other things. Solvents dissolve pigments, binders, and other additives to form a liquidic substance we all know as “paint.” Water is the most common solvent used in paints.
Various additives can be used in paint to increase viscosity and coverage rate. They can also be used to enhance weather resistance, prevent mold growth, and modify other physical properties.
3 Ways to Thicken Latex Paint
Latex paint used to be made with the sap from the Brazilian rubber tree (Hevea brasiliensis). Now it’s made with a lovely manmade compound of chemical polymers that’s added to a water base.
Having a water base makes latex paint low in volatile organic compounds (VOCs). Water also makes it dry faster and easier to clean up. That’s why it’s such a popular choice for both DIY and pro painters.
Latex paint is more elastic than oil-based paints, meaning it is less likely to peel or crack after curing. It’s also gas-permeable, meaning it won’t trap moisture under the painted surface.
Thicken Latex Paint with a Thickening Agent
Your local home improvement store most likely sells a latex paint thickening agent. These are typically made with a substance called hydroxyethyl cellulose (HEC), which is compatible with most interior and exterior latex paints.
You just mix 6 parts of water with 1 part of HEC to create a slurry, then, you wait about half an hour. Then, you mix the slurry into your paint. This is the general method, but be sure to follow the instructions of the product label.
Let Latex Paint Evaporate to Thicken It
One free way to thicken latex paint (or any other type) is to let it dry out. Evaporation means less water, which means less moisture, which means more viscosity (thickness). Do it like this:
- Open the paint can.
- Give the paint a good stirring.
- Leave it to sit, open, in a well-ventilated area.
- Wait 1 hour.
- Stir it well again and check the thickness.
Repeat the process until the desired thickness is achieved. Just be careful to not allow the paint to overthicken and develop dried chunks. Nobody likes that.
Thicken Latex Paint with Drywall Joint Compound
Drywall joint compound, better known as “mud,” can work, in a pinch, to thicken latex paint. The trick here is to just mix in a little bit at a time. So, for a 1-gallon can of paint, add about a tablespoon of mud, and then use a drill with a paddle bit to mix it up thoroughly. Continue mixing in about a tablespoon of mud at a time until the desired thickness is obtained.
PRO TIP: I asked my friend, David Peck from Impeccable Remodeling, his best advice for dealing with thin, runny paint. He explained:
Alan, the best way to thicken paint is to first ensure that it actually needs thickening. So many times, even with so-called “professional” painters, I’ve seen people give the can a quick shake, open it, and pour it directly into their paint pans. The problem is that they didn’t mix the paint well enough to distribute the pigments, meaning it is watery and lacking in its intended color. Always be sure to mix the paint thoroughly, and you probably won’t even need to thicken it!
How to Thicken Acrylic Paint
While latex paints are water-based, acrylic paints are made with chemical bases. The chemical bases of acrylic paints add durability, elasticity, water resistance, and adhesion. Acrylic paints are more elastomeric than latex paints, meaning they can flex when the subsurface expands or contracts due to temperature or positional fluctuations.
Even though acrylic paint typically lasts longer than water-based latex paint, it is also considerably more expensive. The higher price tag is the main reason that more people choose latex for exterior projects, even if the acrylic would provide a superior result. Acrylic paints also contain high levels of VOCs, meaning they are not preferred for most interior applications.
So, generally, acrylic paints are used for coating smaller areas. Plus, acrylics are very popular for numerous arts and crafts applications, because they dry fast and are available in a very wide range of hues. Although acrylic paints are commonly pretty thick to begin with, there are some reasons to make them even thicker.
You can thicken acrylic paints with specialty products like Golden and Liquitex for general thickening purposes, or you can thicken and add texture with gel compounds, sawdust, sand, and even modeling paste. If you use modeling paste, be sure to account for the fact that it dries white, and will likely lighten the paint. Remember to add just a little at a time until the consistency you want is achieved.
PRO TIP: Some people advise using corn starch to thicken paint. I don’t recommend it for a couple of reasons. First, it’s made of corn, and is therefore organic, meaning it can decompose, even after it is mixed into paint and applied to a given surface.
It can actually develop mold, causing you to have to rework the area = not good. Secondly, I understand that times are tight, but maybe think of other ways to save a few pennies. Don’t be such a tightwad!
How to Thicken Oil Paint
If you thin out your oil paint too much, you can thicken it back up by increasing the amount of unmodified paint in the container.
If your oil paint is too thin straight from the container, even though you have mixed it thoroughly from top to bottom, you can use a quality Stand Oil to increase its viscosity. However, be aware that stand oil will increase drying time, and more importantly, create a glossier finish.
There are other mediums that will thicken your oil paint, like Alkyd Butter and Alkyd Gel Medium. Both of these products will thicken oil paint without any major increase in drying time, but they will also create shinier finishes.
If you want to thicken oil paint without creating a glossy finish, consider using a combination of odor-free mineral spirits and beeswax. This technique will create a matte finish while still thickening the paint. A premixed version of this is available in many paint stores. It’s called Cold Wax Medium.
PRO TIP: My experience with oil paints is extensive and basically unpleasant. 3 decades ago, as a young, novice painter, I spent about half of every week using oil-based paint in ritzy homes in upscale neighborhoods. Oil paint has its advantages, but not so much for painters.
It’s VERY messy to work with, permanently stains any and everything it contacts, requires strong solvents for cleaning up your equipment, is LOADED with VOCs and heavy metals, and it costs a lot. My advice: Don’t use oil paint.
My Final Thoughts About How to Make Paint Thicker
Latex paints are the most commonly used, and for good reasons. What they lack in ultimate durability and longevity, they well make up for in terms of low VOCs, high versatility, ease of use, ease of clean-up, and affordability.
Acrylic paints are awesome, but they cost a lot, especially if your painting anything large. And oil paints, well, let’s just say that they and I don’t get along very well!
Thank you so much for reading today and I hope you’ve gained some valuable information about how to thicken paint. Remember that (almost) any mistake you make when attempting to thicken your paint can be reversed. So don’t stress about it too much!