The Anatomy of Watercolors
Here’s a little writeup we did for us to have a shared vocabulary when we talk about paints. In our search for watercolor products to recommend and sell to people, we’ve had to find a good frame of reference in which to compare them.
The Common Ingredients of Watercolor Paints
- Pigment: Pigments are responsible for your paint’s color attributes. Manufacturing considerations in pigments are particle size, tinting strength and dispersability.
2. Brightener: Brighteners enhance the lightness or chroma of finished colors. Too much brightener however can give a white cast to your paintings. They can also compromise the lightfastness of your paints because they do not separate from the pigment particles once mixed with water (This is because they have the same particle size and specific gravity).
3. Binder: Binders bind pigments to the surface of the paper. They also counter capillary action by which paints are dragged down too fast into the paper’s fibers. Traditional watercolor binder is gum arabic.
4. Plasticizer: Plasticizers prevent paint hardening on tube. They also counter problems caused by too much gum arabic like cracking, flaking and making paints appear dark, shiny or leathery. The most commonly used plasticizer is glycerin.
5. Humectant: Gum Arabic mixed with plasticizer are not enough to prevent paint hardening on the tube. A humectant is needed to absorb water from the environment and retain water in the tube. Humectants also extend paint drying time so you can have more fun in playing with colors and effects before they dry. A drawback is that they may increase the staining effect of paints. The most commonly used humectants are honey and corn syrup.
6. Filler: Fillers are used to thicken the paint and standardize the consistency of pigment and vehicle mixtures belonging to the same line. They are also used to subdue intensely tinting pigments, or to reduce ratio of expensive pigments in the paint. Most commonly used filler is dextrin.
8. Water: Water occupies around 15% in volume per tube. It reduces thickness of the vehicle and shortens the time and energy needed to mill the paint although it may also expand some pigments or fillers that absorb it.
9. Other additives:
- Dispersant: Dispersants accelerate and improve milling of pigments in watercolors. They also reduces the dissolving time of paints, although they may promote staining and aggressive paint diffusion. Commonly used dispersant is ox gall.
- Fungicide: Fungicides are used to prevent mold growth in watercolor tubes and in finished paintings.
- Alcohol: Alcohol is sometimes added to shorten drying time or to improve wetting action of washes.
What does this all mean?
With this list, we can take out the easy pickings:
- The difference between artist-grade paints and student-grade paints stems from the ratio of pigment to extender (filler and brighteners)
- Paints with honey can extend their drying time but increase their staining effect too.
- That unusually bright paint may seem impressive at first but will lose its color after a few years.
But we’re only getting started! We’ll start conducting tests on paints, papers and brushes so you can see for yourself the difference among them. Stay tuned!
