Why Does Gouache Crack? A Lesson From My Latest Painting

I recently ran into a problem I hadn’t experienced before while working on a small gouache painting: the paint cracked as it dried.

I was painting a light green object over a dark background. The background was painted with HIMI gouache, while I used Winsor & Newton gouache for the object. Because gouache can reactivate when it gets wet, I was concerned that adding too much water to the lighter paint would pick up the dark color underneath.

My solution was to use the Winsor & Newton gouache fairly thickly to get the opacity and clean edges I wanted.

It worked while the paint was wet. By the next morning, however, the light green areas had developed a network of fine cracks.

Why Did My Gouache Crack?

Traditional gouache can crack when it is applied too thickly. Gouache dries to a matte paint film, and a heavy layer can become brittle as it dries and contracts.

In my case, I also added more paint in areas where the first strokes didn’t give me the smooth coverage or clean edges I wanted. That created an even thicker layer in some places.

The result was a good reminder that more paint isn’t always the best way to get better coverage with gouache.

Close-up of fine cracks in a thick layer of light green gouache paint.
Cracks in the gouache

What I’ll Do Differently Next Time

For my next attempt, I plan to use just enough water to give the gouache a smooth, creamy consistency while keeping it opaque. If the first coat doesn’t provide complete coverage, I’ll let it dry before applying another thin layer instead of continuing to build up wet paint.

I’ll also avoid painting the dark background underneath areas that I know will eventually be a much lighter color. Leaving some of the white watercolor paper exposed should make it easier to achieve an opaque light color without using such a heavy layer of paint.

Can Cracked Gouache Be Fixed?

For now, I’m leaving the cracked paint alone. Adding water could reactivate the gouache and potentially loosen or disturb the already cracked surface.

Once the painting is finished, I’ll check whether the paint is stable before deciding what to do next. I already plan to repaint this particular piece, but I may keep the cracked version too. Sometimes a painting that doesn’t go as planned can still be useful, especially when it teaches you something for the next one.

Unfinished gouache painting of a pickle-themed lighter on a deep purple background, showing cracked light green paint on the lighter body.
Unfinished Gouache Painting “Pickle no good!”

If you’re learning to work with gouache too, you can also read my post, Does Gouache Reactivate With Water?, where I share more of what I’ve learned about layering and working with this medium.

Does Gouache Reactivate With Water?

Yes, traditional gouache can reactivate with water, even after it has dried. It’s one of the things that makes gouache such an interesting medium to work with, but it can also take some getting used to.

When I first started painting with gouache, I quickly learned that “dry” doesn’t necessarily mean permanent. If you add water or wet paint over a dried layer, some of that color can become workable again.

Sometimes that’s exactly what you want. Other times, not so much.

Open HIMI jelly gouache palette with colorful paint cups, brushes and a jar of water beside it.

Why Does Gouache Reactivate?

Gouache is a water-based paint. Unlike acrylic paint, which becomes water-resistant once it dries, traditional gouache can usually be softened again with water.

That means paint that has dried on your palette can often be reused. Add a little water, give it some time to soften, and you may be able to paint with it again.

It also means dried paint on your artwork can reactivate.

If you brush a wet layer over an area you’ve already painted, your brush may pick up some of the color underneath. That can cause the two colors to blend or make the lower layer look disturbed.

Is Reactivating Gouache a Bad Thing?

Not necessarily. It can actually be useful.

I sometimes take advantage of it when I want to soften an area, blend an edge or make a small adjustment to something I’ve already painted. Being able to go back into a dry layer gives gouache a flexibility I really enjoy.

The challenge comes when I don’t want the first layer to move.

For example, if I’ve painted a dark background and then try to add a lighter color on top with a very wet brush, I can accidentally pull some of that dark paint into the new layer. Instead of getting a clean light color, I may end up with something muddy.

I’ve learned that the amount of water on my brush matters just as much as waiting for the first layer to dry.

Sometimes reactivation can actually work in your favor. With my goldfish painting below, for example, pulling some of the dark blue background into the white, flowy fins helped give them a more translucent look.

How Do You Paint Over Gouache Without Reactivating It?

You can’t always prevent gouache from reactivating completely, but a few things help:

  • Let the first layer dry completely. Painting over damp gouache will move the paint much more easily.
  • Use less water in your next layer. A wetter brush is more likely to disturb the paint underneath.
  • Try not to overwork the area. A few deliberate brushstrokes usually work better than repeatedly brushing over the same spot.
  • Use thicker paint for lighter details. If I’m adding highlights or light colors over something dark, I usually want the paint fairly opaque rather than heavily diluted.

And sometimes I simply leave an area alone and come back to it later. Gouache has taught me that continuing to fuss with a section isn’t always the best way to fix it.

Can You Rewet Dried Gouache on a Palette?

Usually, yes.

One of the nice things about traditional gouache is that dried paint doesn’t necessarily have to be wasted. You can often add water and work it back into a usable consistency.

How well it reactivates can depend on the brand, how long it has been dry and the particular color. Freshly squeezed paint and reactivated paint may not feel exactly the same, but dried gouache can still be very usable.

This is also one reason I enjoy working with jelly gouache. I keep the paints moist when I can, but if the surface begins to dry, water can help make the paint workable again.

Gouache Takes a Little Practice

Reactivation isn’t the only thing that took me some time to get used to. One of the biggest lessons I’ve learned with gouache is that the color you see while you’re painting isn’t always the color you’ll have once it dries.

Lighter colors tend to dry darker, while darker colors can dry lighter. I’ve learned to keep that in mind when mixing colors and building layers, especially when I’m trying to match a color I’ve already used. Because of that, I usually mix a little more paint than I think I’ll need and set some aside in a small airtight container. It saves me from trying to recreate the exact color later, especially when I’m adding shadows, fixing a mistake, or cleaning up lines as I put on the finishing touches.

The same is true of reactivation. Once I understood that a dry layer could become workable again, I stopped fighting the paint quite so much.

I learned when to use more water, when to use less, when to let a layer dry and, maybe most importantly, when to stop brushing over the same area.

That’s part of what I enjoy about gouache. It can be forgiving enough to let you go back and make changes, while still making you think about how each new layer will interact with the one underneath.

Like most things in painting, it gets easier the more you use it.