What is Gouache? – Answering your GOUACHE FAQs

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I started using gouache over 5 years ago, and gained a lot of valuable insights. And since doing my huge Gouache Brand Comparison where I compared 12 brands of gouache, I have learned so much about it from each company that I want to share.

So let’s dive in and explore the unique properties of this magical medium!

Unique Properties of Goauche

Typically gouache is described as ‘opaque watercolor,’ but it’s much more than that! They share this in common: pigment suspended in a water soluble binder.

In traditional watercolors, pigments are ground into an extremely fine powder and mixed with a binder of gum arabic. They also often contain other modifiers such as honey, glycerin, ox gall, water, and even fluorescents.

In traditional gouache, pigments are ground up into a powder, but not as finely as watercolor. The larger pigment particles are still very fine to a human eye but are larger than what is used in watercolor paint. The pigments are combined with a binder, typically gum arabic. More pigment is added, which is often why it’s referred to as having a ‘heavy pigment load.’ So compared to watercolor, the paint is more densely packed with pigment. Sometimes other binder ingredients are added such as dextrin (starchy glue), ox gall, honey, and calcium carbonate. There are a lot of misconceptions and false information online about gouache. During my research I contacted the companies directly to clarify information about what is in each brand. I spoke with representatives from their labs. As I continue to explore new brands I will update my database.

Acrylic gouache is similar to traditional gouache except it uses a polymer binder (plastic) which dries permanent. Therefore you cannot rewet it and use it like watercolor or gouache. I’ve shared a post about it here if you’re interested.

After speaking with representatives from several top brands, I learned that they often use proprietary ingredients and do not disclose everything in their paint. They are only required to follow safety standards, otherwise it can be a bit of a mystery. In my gouache database I’ve done my best to dig deeper and find out what is inside each brand. And by the way this secrecy is not exclusive to gouache. The same goes for watercolor, oil, and probably most art supplies.

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Why is my gouache painting “crumbling?”

Because gouache has so little binder compared to other paint, you cannot paint too thickly with it. Once the moisture in the gouache evaporates out of the paint, the paint will crack and crumble off the page because there is not enough binder to hold it there. In order to avoid this, don’t allow the paint to build up too thickly on the page. You shouldn’t be able to see “raised edges” on the paint like this:

What happens when you paint with thick gouache

Is gouache permanent?

When gouache dries is it not permanent in the same sense as acrylics. Gum arabic is a strong natural adhesive, so the pigment is held to the paper fibers tightly. But it’s water-soluble, so the surface of gouache can be rewetted and moved. To me this is one of the best features of gouache. It sometimes reminds me of working with oils, being able to continuously blend into my existing colors. However it does take time to get used to this, just like with oils. I often hear beginners getting frustrated by this trait. You can try using an acrylic gouache underpainting as demonstrated here.

Dry gouache can be reactivated when wet

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Why does gouache dry matte?

Think of pigment powder. Is it shiny? No.

pigment powder
Jacksons Art sells pigment powder, and they have a great article about the process of making your own paint.

Because of the heavy pigment load in gouache and the fact that there is less binder (usually gum arabic), once the paint dries you are left with almost pure pigment held in place with just enough binder to keep it together.

In addition, some brands will use additives such as calcium carbonate to increase the matte finish.

Care must be taken to avoid rubbing the surface of a gouache painting. Doing so will burnish the paint, leaving behind a shiny finish.

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What is Acrylic Gouache? And how is it different?

Acrylic gouache contains a polymer binder (plastic) rather than gum arabic binder (water soluble). The polymer binder makes it permanent, so once it dries you cannot rewet and move the paint like traditional gouache.

In my opinion they should just call it ‘matte acrylic’ instead. In my experience, acrylic gouache doesn’t behave like regular gouache because of it’s modified binder. It behaves more like acrylics. It also doesn’t have the same perfectly matte finish as regular gouache (close, but not quite).

Here’s a very interesting article about chalk.

Does Gouache contain chalk?

Since gouache dries matte, it reminds people of chalk. Chalk itself is made of calcite (either calcium carbonate or calcium sulfate) with other fillers. But high quality gouache does not contain chalk. “Chalky” is an adjective sometimes used to describe the soft pastel look of gouache paintings, but this often has more to do with color choices than the gouache itself. Adding white to a color will desaturate it. It gives it a very soft pastel look. Mixing earthy tones together can result in a more dull mix as well. That, combined with the matte finish of gouache is often mistaken for the look of ‘chalkiness.’

Some brands do add calcium carbonate, a component of chalk. However it’s a miniscule amount compared to the amount of pigment involved.

Cheaper brands will substitute more fillers for less pigment (cheaper to manufacture). This can result in dull color, which can be mistaken for a chalky look.

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Can you combine watercolor and gouache?

Yes. They are very compatible. They are made with the same binder, the only difference is the amount of pigment in each. A common plein air (painting outside) technique is to use a normal watercolor palette and bring a tube of white gouache. Nathan Fowkes is famous for his beautiful studies on location which were later used in art production in several movies. He uses watercolor and adds white gouache to achieve opacity which allows him to layer the paint.

Nathan fowkes painting kit
Nathan fowkes painting outside

Can you use gouache like watercolor?

Yes, you can dilute gouache with water and paint with it the same way you would with watercolor. I recommend using high quality watercolor paper (100% cotton) if you dilute your gouache, so that the pigment can sink into and adhere to the paper more deeply. When using diluted gouache, treat it like watercolor.

I like to start with a diluted underpainting and then paint with gouache on top as demonstrated here.

Painting a forest with watercolor and gouache

Why is some gouache more transparent than others?

In high quality gouache, the higher pigment load of the paint is what makes it more opaque. This means every drop of it is packed with tons of pigment and it dries extremely vibrant with a velvety matte finish. But, some pigments are naturally semi-transparent or transparent, like phthalos and quinacridones. Even in very high quality gouache, these colors will be slightly less opaque than others. So we cannot measure quality in opacity alone, it’s a combination of opacity, vibrancy, and consistency that make a “good” gouache.

How do you varnish or seal gouache?

I’ve shared my experience with cold wax varnish which is my favorite way to seal a gouache painting. You can also seal gouache with varnish, but care must be taken to not disturb the surface of gouache, as it can be reactivated with moisture. I personally love the matte look of gouache, so I don’t like adding a glossy finish. Therefore the cold wax is ideal for me.

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What is this watery/liquid stuff coming out of my gouache tube?

If you open a tube of gouache and notice a clear or yellowish liquid coming out of the tube, that is the binder. There is a thing called binder separation, when the pigment and binder separate while sitting for too long. It can also be referred to as shelf life. The problem with binder separation is that the two substances need to be mixed for the gouache to behave properly. Without binder, the pigment won’t flow or stick to the paper properly. Without pigment, the binder is just useless liquid.

Binder separation in gouache

What can you do about it? Three things.

  • First, you can use a toothpick to stir it inside the tube as best as you can. This can be messy, as you push the paint around it may spill out a little.
  • You can hold the tube upright and squeeze until paint comes out (along with the binder) then mix the two on the palette with a palette knife until they are well blended. If it’s still really runny, it means you don’t have enough pigment.
  • Or, you can squeeze the tube so the binder comes out onto a paper towel. Usually there is just a tiny bit of it, so it doesn’t compromise the integrity of the entire tube. If a ton of it comes out, that’s not good. I’d request a replacement from the manufacturer or seller.

In the photo above you see the liquid pouring out, and it ended up being a disaster. These tubes of Royal & Langnickel were unusable because the binder completely separated from the pigment and none of the above techniques worked. I returned them to the seller because I believe they were defective.

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How do you travel with gouache?

This is very personal and the same setup won’t work for everyone. If traveling abroad, you’ll need to follow the airline rules for liquids. If security asks what it is, you can describe it as watercolor since that’s the closest thing they’ll understand.

Since I usually travel within my own country I have more options. I prefer to use an air-tight palette to travel with my gouache so that it stays in liquid form. My palette is completely leak proof, so if it gets dropped or tossed around in my backpack, the gouache stays put. This palette comes with it’s own water dish and the lid is a mixing tray. It’s a self-contained unit that has been a joy to use.

Travel gouache palette with Etchr Slate Mini

You can also pour the gouache into a watercolor palette and let it dry (like watercolors). When doing this, it’s best to spray the surface of the dried gouache with a fair bit of water, then let it “soak” for about 5 minutes. Depending on how long you let the gouache dry, more or less water and time may be needed.

Which leads me to the next question…

Can you paint with dried gouache?

Of course. Simply drop a 1-3 drops of water into each color and let it soak for about 5 minutes. If you allow the water to soak in long enough, this softens it and you can get some really strong opaque color. Be careful not to add too much water, as it will reduce the opacity too much. It takes some experimenting.

In my experience some brands don’t reactivate as easily as others. From my tests, Daniel Smith gouache is the easiest to rewet and probably my favorite for the ‘dried gouache approach,’ followed closely by Schmincke Horadam, then Winsor & Newton. I could get fully opaque swatches from these every time.

Holbein and M. Graham were difficult to rewet which resulted in more transparent color. This could possibly be mitigated with the addition of Winsor & Newton Watercolor Blending Medium but more testing is required before I can comment on that.

I’ve become more and more interested in using dried gouache so you may see more videos from me on this in the future.

Does granulating gouache exist?

Gouache doesn’t granulate. The pigments do. So if a gouache contains a naturally granulating pigment like Ultramarine, you will notice granulation if it’s diluted enough. At full opacity, you will most likely not see any granulation.

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How do you stop gouache from drying out while painting?

There is not a lot of moisture in gouache compared to other paint so it does dry out faster. This is a bit tricky but overtime you find ways to cope with how fast gouache dries. The main thing to watch out for is you want the surface of your colors in the palette to be shiny. If they start to look matte, they are drying out too much. I have three main strategies to keeping the gouache moist (you can also watch my video here):

  1. Spray bottle. I use a small 10-20ml spray bottle and every 10 minutes or so I give my palette a little spritz of water. Don’t over-water it though, because it will lose opacity.
  2. Use a stay-wet style palette. I’ll share my favorite below.
  3. Add a modifier such as Winsor & Newton Watercolor Blending Medium. This adds moisture without diluting too much (like water does). It makes the paint more fluid, so use sparingly at first. Just one or two drops in each pile of paint is good to start with.

What is the best palette for gouache?

Again this is so personal. Some people only paint inside, some of us paint outside a lot. Many of us do both. But regardless of where you paint, since moisture is important for gouache to behave properly, it is ideal to use a stay-wet style palette. There are many on the market, and you can even make your own.

DIY Stay wet palette for gouache

Above, I show my homemade version using my cheap watercolor palette as demonstrated in this video.

My personal favorite is the Regrass Games V2 palette, because it’s the perfect size for my desk and keeps my gouache moist for weeks. It comes with a special anti-microbial sponge and paper, making the whole setup a breeze to use for keeping my gouache moist.

Redgrass V2 stay wet palette for gouache
Redgrass V2 Stay Wet Palette comes with a sponge and palette paper which I think is the best quality for my gouache.

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What brushes should you use for Gouache?

For a very long time, I used my watercolor brushes for gouache. Eventually I realized how important water control is, and knowing exactly how much water is in my brush was crucial to getting my favorite brush stroke style. I started using synthetic flat brushes because it’s easier to control how much water is in the hairs. I also realized that softer hairs were better for layering gouache. Stiff hairs would typically force my color to blend with the layer below, whereas soft hairs allow me to gently lay the new layer on top. So I collaborated with Craftamo to make a set of my own, meticulously designed to be my “perfect gouache brushes.”

My own designed brushes, collaboration with Craftamo.

Gouache brushes by Sarah Burns and Craftamo

But before that, I did a HUGE flat brush comparison which you can read here or watch in this video.

Can you paint with gouache on any type of paper? Which paper do you use?

Yes, and gouache is less picky about paper type than watercolor. If you like to dilute your gouache like watercolor, then I suggest using thick, 100% cotton paper so that you can achieve the desired techniques.

But I typically use cheaper cellulose paper for my gouache paintings. Since gouache is a bit thicker when fully opaque, it tends to sit on top of the paper more than watercolor. I showed you above what happens when you paint really thick, so obviously avoid that. But generally I paint with it in it’s most opaque liquid form.

Anything above 90 lb / 150 gsm is fine, but the thicker the better. Thinner paper will buckle slightly with the moisture in gouache, but I’ve always been able to flatten them after they dry without issues.

I prefer hot pressed paper for gouache because the paint is able to glide over the smooth paper easily. If you use rough paper, you’ll experience some “brush drag” and not be able to create super crisp lines.

The paper I use the most for gouache is Daler Rowney Aquafine Hot Pressed 140 lb (300 gsm) paper.

I love painting on toned paper, so most of the time I paint in my Stillman & Birn Nova Beige sketchbook.

Painting with gouache on toned paper outside plein air

I hope this post was helpful! Enjoy your gouache adventures 🙂

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Gouache painting on toned paper

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I'm an independent artist living in Scotland. Always chasing the light, and painting the beautiful highlands.

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