Wetting Organic Pigments for Acrylic Paint — How to Mull Color the Right Way
If you’ve ever tried to grind dry organic pigment straight into acrylic medium, you probably discovered the same frustrating problem: the powder refuses to mix. It floats, clumps, or turns into stubborn “fisheyes” that never disperse no matter how long you mull. This happens because most organic pigments are strongly hydrophobic — they repel water-based binders like acrylic emulsions. Some organic pigments are also very light and low density and will simply float on water.
Proper wetting is the missing step between dry pigment and smooth, professional-grade paint. Once you understand the chemistry, acrylic paint making becomes predictable, efficient, and far more vibrant.
Why Organic Pigments Won’t Mix Into Acrylic
Acrylic paint is a waterborne polymer emulsion. The pigment particles must become coated with liquid before the acrylic binder can surround and lock them in place.
Organic pigments are manufactured to be chemically stable and resistant to solvents — great for durability, terrible for dispersion. Their surfaces contain non-polar aromatic structures that trap air and repel water.
So when you dump pigment into acrylic:
Air sticks to the particle surface
Water cannot penetrate agglomerates
The binder cannot attach
Clumps form instead of color development
You are not actually grinding pigment at this stage — you’re fighting surface tension.
Mulling only works after wetting occurs.
The Correct Wetting Strategy
Before adding acrylic medium, you must first convert the pigment from a dry powder into a paste using a compatible wetting liquid. This replaces the air layer with a liquid layer the binder can adhere to.
Step 1 — Pre-Wet the Pigment
Place pigment on a glass slab and add a few drops at a time of a wetting agent:
Best universal wetting liquids
Propylene glycol
Ethanol + small amount of water (fast evaporating)
Triton X100 or other nonionic surfactant solution
Acrylic wetting additives (surfactant solutions)
Using a palette knife, press and smear until every particle darkens evenly. The powder should transform into a smooth butter-like paste.
Important:
You are not trying to thin it — only eliminate dry powder. If you use a surfactant solution, dissolve surfactant in water first to make a 10% solution. Applying too much can cause foaming and pinholes in dry coating.
Step 2 — Mull the Paste
Now use a glass muller:
Circular grinding motion
Firm downward pressure
Periodically scrape and regroup
You will notice a dramatic color shift — this is called color development . It happens because the pigment particles separate into their primary particle size and reflect light correctly. With a palate knife you can "draw down" some of your wetted pigment on a glass plate and shine a light through it to see if agglomerates are broken up evenly.
At this stage the pigment is actually dispersing.
Step 3 — Introduce Acrylic Medium
Only after the pigment paste is fully smooth should acrylic medium of choice be added.
Add small portions and mull between additions.
This prevents shock flocculation — a common mistake where the binder locks pigment aggregates permanently.
Recognizing Proper Dispersion
Well-dispersed paint has:
Glossy uniform appearance
No graininess when spread thin
Maximum tinting strength
No floating specks in a drawdown
Poorly wetted pigment looks dull and weak even if the color is strong in powder form.
Why Wetting Improves Color Strength
Dry pigment exists as microscopic clusters called agglomerates. Light cannot penetrate them efficiently, so the color appears chalky and weak.
Wetting + mulling breaks agglomerates into primary particles:
More surface area interacts with light
Transparency increases
Saturation increases
Less pigment needed per batch
You’re not adding color — you’re revealing it.
Common Mistakes to Avoid
Adding acrylic first
Creates permanent clumps the muller cannot fix.
Adding too much liquid
Produces a wash instead of a grind.
Skipping mulling
Leads to weak tinting strength and poor hiding power.
Trying to disperse in water alone
Water cannot wet hydrophobic pigments without a surfactant or co-solvent.
Advanced Tip — Why Glycols Work Best
Glycols act as a bridge between hydrophobic pigment and water-based acrylic:
One end interacts with pigment surface
The other interacts with water and polymer emulsion
Prevents reflocculation after grinding
This is why professional dispersions nearly always contain humectants or surfactants.
Final Thoughts
Making your own acrylic paint is not just mixing powder into binder — it’s a controlled surface chemistry process. The real secret isn’t force… it’s compatibility.
Once the pigment is properly wetted, the muller suddenly feels effortless, the color blooms instantly, and the paint behaves like a commercial product.
Master wetting, and you master dispersion.
Your pigments already contain the color — wetting simply unlocks it.
Be sure to fully investigate the properties of the pigment in question! Both from the manufacturer as well as independent sources! Some pigments are unsuitable for acrylic mediums because of the mediums sensitivity to pH swings. With proper due diligence and care, making your own acrylic paints can be both rewarding and money saving. Not to mention the intimate bond you’ll like form with your materials!
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