Watercolor binder is a simple mixture of gum arabic, water, and a small amount of glycerin. You can make a functional batch with just three ingredients in under an hour, though getting the ratios right makes the difference between paint that flows beautifully and paint that cracks in the pan.
What Watercolor Binder Actually Does
Gum arabic is the core of every watercolor binder. It’s a natural resin harvested from acacia trees, and it works because of its unusual molecular structure: one part of the molecule is attracted to water while another part grabs onto pigment particles. When you brush watercolor onto paper, the gum arabic carries pigment across the surface and then, as the water evaporates, locks those particles onto the cellulose fibers. Without it, dry pigment would just dust off the page.
Pure gum arabic dries to a hard, brittle block. That’s why commercial watercolors always include a plasticizer (to keep the paint flexible) and a humectant (to help dried paint reactivate with water). In homemade binder, glycerin fills both roles.
The Basic Recipe
This recipe produces enough binder for several batches of paint. You’ll need a kitchen scale or measuring cups, a heat-safe container, and a stirring utensil.
- Gum arabic powder: 2 parts (e.g., 125 grams)
- Hot water: 4 parts (e.g., 250 grams), distilled if possible
- Glycerin: about 1 tablespoon per 125 grams of gum arabic
Heat the water until it’s hot but not boiling. Boiling can break down the gum arabic and weaken its binding power. Slowly stir the gum arabic powder into the hot water. It will look lumpy and cloudy at first. Keep stirring until the powder dissolves completely, which can take 10 to 20 minutes. Some makers let the mixture sit overnight and stir again the next day to catch any undissolved clumps.
Once the gum arabic is fully dissolved, add the glycerin and stir thoroughly. The finished binder should have a consistency similar to honey or thick syrup. If it’s too thick, add small amounts of warm distilled water until it flows smoothly. If it’s watery, you can let it sit uncovered for a few hours so some moisture evaporates.
Getting the Glycerin Right
Glycerin is the ingredient that requires the most judgment. Too little and your dried paint will crack in the pan, especially in dry climates where moisture evaporates quickly. Too much and the paint stays tacky, takes much longer to cure, and can feel gummy under the brush.
Start with a conservative amount, roughly one tablespoon per 125 grams of gum arabic powder. You can always add more glycerin later when you’re mixing the binder with individual pigments. Some pigments need more than others. Finely ground pigments like micas tend to need less glycerin because their particle structure already produces a smoother paint. Coarser or moreite pigments may need a bit extra to stay flexible once dried.
Some recipes call for honey instead of glycerin, since honey acts as both a humectant and a mild plasticizer. However, honey introduces sugars that attract mold, and many makers find their paints re-wet just fine without it. If you do use honey, treat it as an addition alongside glycerin rather than a replacement, and expect to need a preservative.
Preserving Your Binder
Gum arabic dissolved in water is an invitation for mold. Without a preservative, homemade binder can spoil within a month, especially in humid environments. One maker reported visible mold on both the stored binder and finished paint pans within weeks of mixing a batch that used honey and no preservative.
You have two main options. Clove or thyme essential oil is the gentler choice: add 1 to 2 drops to your batch and mix thoroughly. Clove oil has natural antifungal properties, and binder stored in the refrigerator with clove oil has lasted 14 months or more without signs of spoilage. For stronger protection, half a teaspoon of sodium benzoate per batch acts as a chemical preservative and extends shelf life further.
Regardless of which preservative you choose, store the binder in the refrigerator between uses. There’s no benefit to keeping it at room temperature, and cold storage significantly slows bacterial and fungal growth. Even with preservatives and refrigeration, most makers recommend mixing only what you’ll use within a few months rather than preparing a year’s supply at once.
Optional Additives
Once you have the basic binder working, a few additions can fine-tune how the paint behaves on paper.
Ox gall is a traditional wetting agent that reduces surface tension, helping paint flow more evenly across the paper instead of beading up. It’s typically added at the painting stage (a few drops in your water cup) rather than mixed directly into the binder. If you do want to incorporate it into the binder itself, start with just a drop or two per batch. Too much ox gall can make the paint spread uncontrollably.
Troubleshooting Common Problems
Paint Cracks in the Pan
Cracking is the most common issue and almost always means the paint lacks enough plasticizer. Add a drop of glycerin directly to the cracked pan, let it absorb, then re-wet and smooth the surface with a brush. If cracking keeps happening across multiple colors, increase the glycerin in your next batch of binder. Dry climates make cracking worse because the paint loses moisture faster than the binder can hold it together.
Paint Won’t Re-wet
If dried paint resists reactivation with water, the binder ratio may be too low relative to the pigment. When you mix binder with pigment, the ratio varies by color, but a good starting point is roughly equal parts binder and pigment by volume. Dense, heavy pigments like earth tones often need more binder. If a finished pan won’t re-wet, you can brush a thin layer of diluted gum arabic solution over the top and let it dry.
Paint Stays Sticky
Tackiness that never fully resolves points to too much glycerin or honey. There’s no easy fix for an already-poured pan other than waiting longer for it to cure. Some overly glycerin-heavy paints do eventually firm up after several weeks. For future batches, cut back the glycerin and test a small amount before committing a full pigment mix.
Binder Is Lumpy
Undissolved gum arabic creates gritty spots in your paint. If stirring doesn’t resolve the lumps, strain the binder through a fine mesh sieve or cheesecloth. Some makers sprinkle the powder over the water surface and let it hydrate for an hour before stirring, which helps the particles dissolve more evenly than dumping it all in at once.
Mixing Binder With Pigment
The binder itself is only half the process. To make actual watercolor paint, you combine the binder with dry pigment powder on a glass surface (a glass muller and slab is traditional, though a palette knife and smooth tile work for small amounts). Add pigment to the binder gradually, mulling in a circular motion until the mixture is smooth and free of visible granules. The goal is a consistency like toothpaste.
Different pigments absorb binder at very different rates. Synthetic organics tend to be pigment-hungry and need more binder, while natural earth pigments can feel oily if you use too much. Keep extra binder and extra pigment nearby so you can adjust on the fly. Once mixed, press the paint into pans or half-pans and let them cure for at least a few days before painting with them. Some colors benefit from a week or more of curing time.