Gouache paints are very similar to watercolors but have some significant differences.
Gouache is a style of painting that was first used to lighten documents because the paint contains white pigment and can make things lighter. This has evolved into a painting medium similar to watercolor. Gouache is often favored over watercolor because the use of gouache does not require a person to protect the white area of the picture like watercolors do.
Canvases
Since gouache painting is water-based, the canvases must also be able to handle water. For example, a person should not paint with regular sketching paper because it will not be heavy enough to withstand the water used. Anything that says it is safe for watercolors will work with gouache, so look for this when buying canvases. Clayboard is another option as it will soak up the paint and color used. If you want to use paper, use thick paper, like watercolor paper.
Watercolor Combination
You can combine gouache and watercolor in the same project. The main difference between the two is that most gouache paints have white pigment mixed in, so the use of watercolors can darken the picture because they contain no white. If you are using more watercolors than gouache, consider protecting the areas you want to keep white even though you are using gouache. This is because the watercolor may overwhelm the white pigment contained in the gouache, allowing the white areas to be polluted by the colors.
Layer Thickness
Using layers that are too thick may cause the picture to crack and peel because the binder from the many layers dries at the bottom and weakens them. However, using too little paint will make the picture a lighter color. Aim to have a mixture of color so that the desired shade can be reached in a few coats of paint. Add paint and water as needed to achieve this.
Rewetting Paintings
Like with watercolors, gouache paintings can be wetted again once they are dry. This provides you ability to smooth out lines between colors that you may not have wanted. It gives the artist a choice to go back and touch up the picture later without having to add too many extra layers. Don't make the painting too wet though, or cracking and peeling may occur.
