What a watercolor medium is
In watercolor, a medium is an additive mixed with paint or applied to the paper to change how the paint behaves. Mediums can alter flow, texture, transparency, drying time or how the pigment settles. The word is also used more loosely for watercolor itself as a painting medium, but in a supplies context it usually means these additives.
Mediums are optional. Plenty of excellent paintings use only paint, water and paper.
Common types and what they do
- Gum arabic: The binder in watercolor paint (it is also the binder in homemade plant paint). Adding a little more can deepen color, add gloss and slow drying. Too much can make dried paint crack or stay sticky.
- Ox gall: A wetting agent that helps water spread more evenly over slick or sized surfaces. Traditional ox gall is animal-derived; synthetic alternatives exist.
- Flow improver or wetting agents: Help washes spread smoothly.
- Granulation medium: Encourages pigment to settle into the paper’s texture for a grainy effect.
- Texture or impasto mediums: Add body to paint for thicker effects. See texture art painting for related methods.
- Blending or slow-drying mediums: Extend working time for blending.
- Masking fluid: Technically a resist rather than a paint additive; it protects areas of paper from paint and is removed later.
Check the manufacturer’s guidance for each product, as formulas vary.
When a medium is worth using
- You want more time to blend a wash
- You are painting on a surface that repels water
- You want a specific texture, such as granulation
- You need to protect highlights with a resist
If you are still learning basic washes, you may not need any of them. See our beginner supplies guide for the core kit.
Can you make a medium at home?
Some artists mix simple homemade versions, most commonly from gum arabic and water. Results vary with ingredients and proportions, and homemade products may not keep well. If you try it, make a small batch, label it and test on scrap paper. Commercial mediums are made to be more consistent.
How to use a medium
- Start with a very small amount; mediums are easy to overdo.
- Mix thoroughly into the paint on your palette, or apply it to the paper first if the product directs that.
- Test on a scrap of the same paper.
- Wait for it to dry fully and judge the final look, since wet paint appears different dry.
Testing and storing
Keep notes on what you added and how much. Store mediums tightly closed, away from heat, and follow the label for shelf life. Rinse brushes thoroughly after using sticky additives.
Mediums can also change how transparent your paints appear; see transparent vs opaque watercolor.
FAQ
What medium is best for watercolor painting? It depends on your goal. Gum arabic for richness, ox gall or flow improver for even washes, granulation medium for texture.
What is a watercolor medium? An additive that changes how watercolor paint flows, dries or looks.
Do beginners need a medium? Usually not at first.