Illustrator Catherine Gura asked me some questions about the paint consistency of gouache, and I wasn't sure of the answers, so I asked her to do some tests and report back. Here's what she found:
"The test: first, I took six different brands of gouache and tested them right out of the tube. Then I placed fresh paint into full size pans and let them dry for five days, at which time I reactivated the gouache with water and painted.
The brands
Utrecht Designers
Materials
14 and 15 ml. tubes of gouache (Winsor and Newton)
a #6 brush so I could get a good load of paint
Crescent HP Illustration Board: medium weight.
Gum arabic (by Rublev Colors)
and glycerin, vegetable source.
Glycerin and Gum Arabic Tests
I added three drops of gum arabic to a pan of Winsor and Newton gouache, and added three drops of glycerin to another pan of W and N gouache, and let them dry for five days, and reactivated them.
Results: Paint consistency
All of the gouache brands were thicker and creamier right out of the tube. With the exception of Winsor and Newton, I found it difficult to reactivate the paint: the gouache was noticeably thinner and felt like using watercolor. The W and N was thinner, too, but less resistant to rewetting.
Winsor and Newton: the original gouache cracked minimally in the pan; the pans with gum arabic and glycerin did not crack at all. The gum arabic made the gouache a little glossier; the addition of glycerin was the glossiest.
Winsor and Newton: the original gouache cracked minimally in the pan; the pans with gum arabic and glycerin did not crack at all. The gum arabic made the gouache a little glossier; the addition of glycerin was the glossiest.
Results: Smell
Schmincke: an older tube smelled badly, the second tube was new, and had only a slight chemical smell
Holbein: no smell
Daler Rowney: slight smell
Utrecht: strong petroleum smell
M. Graham: slight chemical smell, did not smell of honey
Winsor and Newton: mild chemical smell: like school poster paint
Schmincke: an older tube smelled badly, the second tube was new, and had only a slight chemical smell
Holbein: no smell
Daler Rowney: slight smell
Utrecht: strong petroleum smell
M. Graham: slight chemical smell, did not smell of honey
Winsor and Newton: mild chemical smell: like school poster paint
Conclusions
• For best results, I would recommend working with gouache directly from the tube.
• If one wished to make a portable palette, one could set up pans of gouache: I would recommend W and N or Schmincke.
• Gum arabic made the gouache slightly glossier, and glycerin the glossiest, but both were thinner.
• I will continue to work with Winsor and Newton. For the price, I did not find Schmincke noticeably better than W and N, but I tested only one color.
• For best results, I would recommend working with gouache directly from the tube.
• If one wished to make a portable palette, one could set up pans of gouache: I would recommend W and N or Schmincke.
• Gum arabic made the gouache slightly glossier, and glycerin the glossiest, but both were thinner.
• I will continue to work with Winsor and Newton. For the price, I did not find Schmincke noticeably better than W and N, but I tested only one color.
• I would highly recommend avoiding Utrecht: the petroleum smell was awful.
• Holbein was thick and creamy.
• Winsor and Newton gouache dries with a slight sheen without any additives.
Here is my chart: I had to patch my scan together, and a photo of my paints."
----
• Holbein was thick and creamy.
• Winsor and Newton gouache dries with a slight sheen without any additives.
Here is my chart: I had to patch my scan together, and a photo of my paints."
----
Thank you, Catherine. Check out her website
Previous posts:
Most of the original paintings in this post are currently on exhibit in the 
