Working on a gouache palette
Gouache is typically made of water, pigments (more than in typical watercolour) a binding agent (gum arabic, dextrin), and often a neutral compound as an opacifier. It might be plain chalk (calcium powder) or white pigment like titanium or zinc white. This neutral compound makes light colours dry darker, and dark colours dry lighter, which can be a bit trying. But who doesn’t like a good challenge?
The only real difference between gouache and watercolour is the opacity. Very opaque watercolour, like cadmium red, or Naples Yellow which contains zinc white, could be considered gouache. The line between both is a bit blurry. In France during the nineteenth century and most of the twentieth, boxes of watercolour came with a little tube of China white to readily transform the watercolour in gouache when necessary.
When painting with watercolour, it's not recommended to add white, to avoid muddying the colours. Well, that's just what gouache means. Gouache is a French term, from the Italian "guazzo", which translates into “gouache”, but has an etymology linked to mud. I love how it's put : gouache is muddy watercolours. Let's waddle.
I went back to gouache mostly to play with colours. These days I'm working on the intersection of cultural colours with colours as products, a vast subject. I'll talk about in in another post. For my research I needed a large array of pigments and colours. I couldn't buy all the colours I wanted in yet another medium, so I decided to go with what I had in stock. Browsing my shelves I found: gouaches in little cakes I bought for my son, cheap but pretty watercolours untouched because they were muddied with white (horror) or too opaque (lots of cadmiums and other somewhat toxic colours that I put aside but can be used with proper care), some Irodori Holbein traditional Japanese watercolours which are really nice but very opaque (so much pigment!), and some tubes of gouache from different brands, the most lovely being the most scarce in my stash, beautiful Fine Gouache from Holbein. Thinking about it, I'm really fond of Holbein products and wish they were more readily available in Europe.
Apart from the tubes, the material I gathered was labelled anything from paint to watercolours, not gouache, but I could tell, sometimes with a little research, that they had in common to be soluble in water, had pigments in different dosages, that the neutral compounds and binding agents were similar, and if not, miscible. So, they were good material for gouaches mixes.
Watercolour has to be transparent or it can ruin a painting. With gouache it’s the contrary. It has to be opaque, beautifully matte, and not streaky. What I had in my stash made it complicated get saturated, pure colours, but gave a large array of possibilities for work with coloured grays, pinks, pastel and subdued colours that are very difficult to create in watercolour. As I wanted to work with subdued colours and lovely coloured grays, it was a good start.
There's a margin of error in my choices of materials, and room for catastrophic results in terms of lightfastness and durability. I decided to follow the great master of watercolour and gouache himself, Turner, in his love for experimentation, and go for colour before durability. Let's play!
I will go through what I tried (and failed), more than really writing a tutorial, so you can learn from my experience, and decide if you want to give it a go, too.
First, the material.
A big tube of titanium white gouache. You could go for “china white” which is mostly zinc white, but titanium white works so much better as an opacifier. You can use calcium powder as a neutral agent, too, but beware: it can turn your mix into plaster very easily. I did try and had some lovely, very matte results, but it turn to the crumbliest mess very easily.
Watercolour, gouache paints, etc, any paint that can be mixed in water and re-wet, so forget about acrylics or acrylic gouaches. You could go for pigments but that’s another messy story, and you would need then a binder like gum arabic too. I might try that…another time.
A palette with small, deep wells. I found that an empty watercolour box with half pans was just the thing. You might want something bigger if you plan to paint posters or large formats. I paint in a sketchbook and don't need large quantities.
A dropper, dripper, anything that will help you wet your paints with a big fat drop of water. You could do that with a brush but I find it gets messy easily. An old medication dropper is fine, a toy teapot just adorable.
Not your favorite brushes as it’s hard on them. Thin ones are nice to mix and test small samples that dry fast.
A big pot of clean, warm water to wash your brushes, and a rag to dry them. Gouache and watercolour dilutes better in warm water.
Glycerin. You’ll find tiny little bottles of glycerin with bakery products at the supermarket. I’ll explain later.
Now, mixing and testing.
I recommend testing on good paper as you go, with little strokes that will dry very fast, so you get a good idea of the end result. It requires a bit of patience but it's real fun. I made a full page of tiny florals while testing my first batch.
Gouache is made of :
an inert material
All your paints, including the watercolours, contain a binder so you don't need to add one. I hope you have easy access to water.
If your mix is transparent or streaky, you need to add a neutral material (go for titanium white). For rich, darker colours, you might need to buy gouache. I didn't have to as most of my darker colours tolerated a bit of white, and my Irodori watercolours provided what I needed for the darker tones.
Most binders and pigments are miscible. I only had a problem once, with an old cheap watercolour, a fake cobalt violet that kept separating. All my other colours mixed well, from the very expensive watercolours to the cute kids paints.
Proceed like this:
In a clean little pan, put a little diluted watercolor, a bit of gouache, whatever you want to mix. Test. If it's transparent, add either paint with a high level of pigments, or some titanium white. Test and mix again until happy with the result.
Surprisingly you'll need a lot of white to mix pastel and light colours, and a little white gouache in a dark colour will still dry very dark but with a nice opacity. If the mix is too dense, add water, if it's too liquid, let it dry.
The rule of thumb is that you’ll need way more white than you think. For very light colours, start with white and add tiny drops of colours.
Your end mix should be a thick liquid like milkshake or drinkable yogurt, perfect for use on paper.
Up till then thats easy peasy. Unless you tried to add some calcium powder like I did, it's nothing more than mixing colours and water in a little well.
Now here comes the real problem: conservation and re-wetting.
If you're an acrylic artist, you're used to trash the paint after every session. It dries and can't be re-wet. If you're a watercolour artist, you'll keep your palette and know how to re-wet it by spraying water on it and wait until it's soft again. Now this should be possible with gouache, and sometimes it works, but most of the time
You come back to your palette after a few hours and it's a dry messy crumble, and even worse, even if it's not crumbly, it's super difficult to re-wet to the soft consistency you need to work smoothly.
Why is it crumbling when watercolour doesn't? Watercolour contains a plastifier, like honey, to help keeping it moist and elastic. Gouache contains a neutral agent that crumbles.
So what can you do? Add a plastifier! Most common are honey, sugar, and glycerin. I didn't want to try honey. It felt weird to use bees’ hard work for fun…and my cat loves it so it makes painting way too dangerous and messy. I wasn't sure of sugar, should I make a sirup, do I use fructose? So I went instead for glycerin. It comes pure in little bottles and is used to make cake icings smoother. I guess you could try sugar or honey if you can't find it, but as I hear glycerin works better as a plastifier. Now beware: just like too much calcium powder will ruin your paint, too much plastifier will have an adverse effect, too. Paint will become shiny, take forever to dry, or worse, will stay sticky and never dry.
So put just a little drop, from the tip of a toothpick or the point of your brush, and that enough for a half pan. It will make it smooth and ready to go when you will re-wet it. Your paint might crumble or dry solid in the long term, but at least for a few days, when you come back to your palette, add some water and it will be easy to soften. It made big change to the way I work! I haven't tested the glycerin mix in more than a few days myself. I will put some of my paint aside, check in a few weeks, and write an addendum to this post. Until then, I’m the proud owner of a little palette with exactly the colours I wanted, ready to use when I want, and I’m quite happy!
Just don't do the same mistake as I did and move the palette when it's still wet enough to drip. I was lucky it didn't make too much of a mess and only one colour was spoiled. Enjoy!