You could buy another set of paints when you need thicker acrylic paint, but that’s expensive. A much more economical solution is to thicken the paints you already have.
How do you make acrylics thicker? Select an acrylic gel that’s thicker than the paint you’re using and mix it into the paint. You can also use molding paste, or thickening additives. DIY solutions, such as adding flour or joint compound to acrylic paint will work but there are disadvantages.
Below is my YouTube video that covers most of the topics in this post.
In this post, I test out a variety of gels, additives, and DIY solutions for bulking up acrylic paint. I include a beginners guide to acrylic gels that should get you started with using gels. In the above YouTube video I use Liquitex super heavy gel to create thick textures.
Table of Contents
Which Gel Should I Use To Thicken Acrylic Paint?
Different manufacturers have slightly different names for acrylic gels and pastes. There are numerous gels to choose from which can be intimidating.
Fortunately, it’s not that complicated. A good starting point is to choose a gel that’s thicker than the paint you’re using, then select the sheen that you prefer: gloss, matte, or ultra matte.
For example, regular acrylic gels are basically the same thickness as heavy body acrylics. So adding this kind of gel to heavy body acrylics won’t have much of an effect except for making the paint more transparent.
To make heavy body acrylics even thicker, you need to use a thicker gel such as super heavy gel from Liquitex or heavy gel from Golden.
If you’re a beginner, “heavy body” and “soft body” refers to the thickness of the paint. You can find out which acrylics you have by reading the label on the tube or bottle.
Since all of the gels are thicker than fluid acrylics, you can use any gel to make them thicker. Which gel you select depends on how thick you want to make your paint.
Acrylic Gel Example
Below is an example of Liquitex soft body acrylic paint mixed with two different gels. The top image is soft body Cobalt Blue Hue straight from the tube. Soft body acrylics aren’t as thick as the Liquitex heavy body acrylics. They’re good for creating smooth and flat areas of color without brushstrokes. Liquitex acrylics have a satin finish when dry.
In the second photo, I mix regular gloss gel with the same Cobalt Blue. This makes the paint thicker so I can build up some textures with the palette knife. It dries to a glossy finish but there are matte and ultra matte gels available. Adding gel to the paint increases the transparency slightly.
The third photo is the same Cobalt Blue mixed with Liquitex Super Heavy gloss gel. This gel is thicker than heavy body acrylics so you can use it to build up some very heavy textures. It’s available in gloss and matte.
Gels allow you to use one type of acrylic paint and achieve a wide range of thicknesses with it.
The Different Types of Gels Explained
Below are the main types of gels that you can use to make your acrylics thicker. I include the different types of modeling pastes too. As I mentioned previously, manufacturers have different names for similar products.
I usually recommend using the gels from the same brand of paints that you use. This should keep things simpler if you’re a beginner. Of course, if you like to experiment, there’s nothing wrong with mixing brands of acrylics–including mixing brands of acrylic gels.
Soft Gel
Golden’s soft gel is thinner than the regular gel.
It doesn’t retain the bristle marks of your brush as well as the thicker gels. This makes it useful for creating transparent glazes but it’s not the best choice for creating thick impasto paintings.
If you’re using fluid acrylics you can add soft gels to make them a little thicker, but you won’t be able to create brushstrokes that retain the bristle marks, or crisp palette knife marks.
Regular Acrylic Gels
Regular gels have the same consistency as the heavy body acrylics. You can use them to make fluid acrylics thicker so that you can create some impasto textures in your paintings.
Adding regular gel to heavy body acrylics will only make them more transparent. This is useful if you want to increase the transparency without losing the thickness of heavy body acrylics.
You’ll want to use the heavy or extra heavy gels to make heavy body acrylics thicker.
These gels will help you to retain the high peaks and sharp edges that your painting knives create.
Heavy & Extra Heavy Acrylic Gels
The names of the extra thick gels vary by manufacturer but they each offer very similar products.
As I mentioned previously, regular gel is approximately the same thickness as heavy body acrylic paint.
Heavy, extra heavy, and super heavy gels are even thicker.
To me, these gels seem thicker than oil paints. You can apply them with a palette knife or a painting knife and they retain tall peaks with sharp edges.
In case you’re wondering, a palette knife is shaped for mixing paint on a palette. Painting knives are made for applying paint to the canvas and are available in a wide range of shapes and sizes.
Of course artists use them interchangeably and there’s nothing wrong with that, if it gets the job done.
I’m currently using the set of painting knives from Liquitex. (This is an affiliate link that leads to Blick Art Materials which means if you click on the link and make a purchase, I receive a commission at no cost to you).
What’s great about this set is that you get 6 palette knives in a variety of sizes. They’re affordable and they have been working well for me.
You can apply thick acrylic paint with a brush too, but you’ll need a brush with stiff bristles. Otherwise, you won’t be able to move the paint around very well on the canvas.
The bristle brushes that are used with oil painting will work, but hog bristles tend to splay when exposed to water for extended periods of time.
There are synthetic nylon bristle brushes that will last longer when painting with acrylics.
Modeling / Molding Paste
Modeling paste, also known as molding paste, is essentially acrylic gel that contains marble dust.
It dries to a hard surface and should be used on a rigid surface such as a wood panel.
There are flexible modeling pastes available too. Another option for using modeling paste on canvas is to mix it with an acrylic gel to make it more flexible.
Modeling paste is white and opaque, so it will lighten the colors as you add it to your paint.
Another way to use modeling paste is to build up the textures with the paste and allow it to dry. Once it’s dry you can paint over it with any type of acrylic paint.
Light Molding Paste
Applying an excess of modeling paste to a large painting adds a lot of weight. This can cause a few problems.
Very large canvases can actually begin to sag because of the extra weight. Extra care has to be taken when hanging heavy paintings so they don’t fall off the wall.
If you sell your work online, you should also consider the fact that the extra weight will increase your shipping costs too.
Both Golden and Liquitex offer lightweight modeling pastes that weigh significantly less than the regular pastes.
I have tried the light molding paste from Golden and it seems to dry with a “springy” feel to it when it’s dry. It’s definitely much lighter– Golden claims that it’s 67% lighter than regular molding paste.
How to Make Acrylics Thicker – DIY Solutions
If you’re looking to save money on art supplies you may be considering alternatives to acrylic gels and mediums to thicken your paint.
When it comes to thickening acrylic paint, the two most common substances artists experiment with are flour and joint compound. I’ve seen other artists use corn starch but I feel it’s similar enough to flour that the results would be the same.
These household items are more affordable than acrylic gels, but do they work?
Using Flour to Thicken Acrylics
I think people consider using flour to thicken paint because flour is useful as a thickening agent in the kitchen. For example, flour is often used to thicken gravy and sauces.
It’s also used in papier mache so you may be wondering if you can use it to thicken acrylic paint.
While adding flour to acrylic paint will make it thicker, there are a number of downsides to consider.
The first issue is that it makes the paint dry faster. Acrylic paint dries fast enough as it is, and adding a dry powder to it will make it dry even faster.
Another quality of flour is that it becomes springy and elastic when you add water to it. Adding water to flour forms a dough that’s stretchy. The purpose of kneading dough is to develop the gluten and to make it more elastic.
This is not a quality you’re looking for in a paint. The paint becomes somewhat “gummy” as you mix the flour into it. You also have to mix colors as you paint and the extra mixing would probably make this problem worse.
The brush doesn’t work that well with it either. The paint doesn’t retain the bristle marks as well as it would with pure acrylic paint.
The flour gives acrylic paint a coarse texture which I kind of like. If the course texture is something that you’re trying to achieve, then I’d recommend using a texture gel such as Liquitex ceramic stucco (affiliate link to Amazon).
One the largest drawbacks to using flour to thicken paint is that it makes the paint brittle. I flexed the paint samples after they had a few days to dry and they cracked. It made loud snapping sounds as I bent the paper.
You can see the cracks at the top of the green paint sample above.
The joint compound has the same issue. In comparison, the acrylic paint that I mixed with gel remained flexible after it was dry. I folded the leftover paint on the palette paper in half and there was no cracking. It looked undamaged after I flattened it out.
Mixing Joint Compound With Acrylic Paint
Joint compound is used to seal the cracks between the joints in drywall. It comes in plastic buckets and it’s ready to use. It’s more affordable than acrylic gel but does it perform any better than the flour?
When I mix joint compound into acrylic paint I find that it’s very gritty. It feels as though I’m mixing sand into the paint.
You may not notice this if you use a brush to mix your paint.
However, the main disadvantage of joint compound is that it has a tendency to crack, especially on a flexible support like canvas or paper.
Joint compound is light gray and opaque so it will lighten your colors as you add it to your paint. The white flour didn’t have this problem as shown in the photos below.
These DIY solutions may suffice if you’re working on a school project that only has to last for a few weeks or months.
Acrylic gel is more expensive than joint compound, but it’s much more flexible and durable.
I recommend using acrylic mediums for any type of artwork that you care about and want to last a long time. This is especially true if you intend to sell your work or give it away to friends or family.
The Basics of Using Acrylic Gels
Now that you have some idea of which gel you want to use to thicken your acrylics with, you will probably have a few questions on how to use it. There’s a lot of technical information online about gels, but below are the most important points that will help you get started.
How Much Gel Can You Add to Acrylic Paint?
Acrylic gel is basically acrylic paint without the pigment. You can add as much as you want to the paint because it’s almost entirely made from acrylic binder.
Acrylic additives are different from mediums because they don’t contain any binder. The only additive that will thicken acrylic paint is Liquithick from Liquitex. The directions indicate that you should not add more than 25% of it to your paint.
However, the regular acrylic gels are a different story. In fact, you can apply clear gel directly to the canvas without mixing any paint into it. Some artists create thick textures with the gel, and then paint over it with acrylics after it dries.
Another thing to keep in mind is that the paint will become more transparent as you add more gel to it.
Acrylic Gel Is White When Wet but Dries Clear
Gels are white when wet but they dry clear. Adding gel to your colors will temporarily lighten them. The gel clarifies as it dries which makes the color darken slightly.
Acrylic paint dries darker even if you don’t add gel to it. This is because the acrylic emulsion they use to make paint is also cloudy.
If you’re not aware of this issue, then you may become frustrated when your painting dries a little bit darker. The difference is more pronounced with some colors more than others- you may not even notice the shift in color.
With some experience you will learn how to compensate for this effect by mixing your colors just a little bit lighter so that it will dry to the shade that you desire.
Acrylic Gels Shrink as They Dry
Have you ever had the experience of building up textures in a painting, and then when you come back the next day the texture doesn’t look as tall?
It’s not your imagination, acrylic gels shrink as they dry.
Acrylic paints and gels contain water and it evaporates as it dries. When this happens it loses some volume.
You won’t notice the shrinkage as much if you paint in thin layers. But you may start to notice it if you apply the paint in very thick layers.
One way to reduce this is to use the high solid gel from Golden. It contains more solids so it doesn’t shrink as much as regular gels.
Gels and Surface Sheen
Another property of gel that you have to consider is the surface sheen.
Gels are normally glossy, but they’re available in matte, and ultra matte. Matting agents are added to the paint to give it a matte appearance. Thick layers of matte gel will have a cloudy appearance, similar to wax.
You can use the matte gels to create matte acrylics or to simulate the appearance of gouache. The more convenient solution is to buy acrylic gouache. You may want to read my full review of Liquitex Gouache, which includes a demo video.
Golden does offer semi gloss gels, but you can also create your own by mixing gloss gel with matte gel. You can control the amount of gloss by adding more or less of the matte gel.
Can You Use Gesso to Thicken Acrylic Paint?
While there’s nothing wrong with adding gesso to acrylic paint, gesso won’t make the paint thicker.
In fact, Gesso has the consistency of fluid acrylics so adding it to heavy body acrylics would actually thin them out.
The only exception to this is if your gesso is extra thick. Liquitex offers super heavy gesso (shown above) which you can use to thicken acrylic paint. It’s not very common in craft or art supply stores so you’ll probably have to order it online.
Keep in mind that gesso dries to a matte finish so it will make your paint more matte.
Another issue is that gesso is an opaque white so adding it to your paints will lighten the colors.
Conclusion
The DIY tests were fun to conduct but I still recommend using acrylic mediums for thickening acrylic paint instead of flour or joint compound.
If I had to choose a DIY material for thickening acrylic paint I would choose flour. It’s much cheaper, non toxic, and it didn’t affect the color of the paint as much as the joint compound. I also preferred the coarser texture.
Adding flour to acrylic paint may work in a pinch for a short term art project that requires thick textures. Art supplies are expensive and I know what it’s like to be an art student on a budget.
Acrylic polymers are designed to be flexible and last a long time without cracking or yellowing. They perform well when you apply them with a brush or palette knife.
Gels will allow you to control the surface sheen, the thickness, and the transparency of the paint. You can build up thick and bulky textures without having to worry about your artwork falling apart as it ages.
If you’re further along in your art career or you’re really into painting as a hobby, then I recommend that you splurge and try out some of the acrylic mediums.
