Casein (Milk Curd) Paint
Sour-milk paint — the medium of barns, posters and Mexican muralism.
Make glue out of milk curds, then stir in pigment.
- ▸Casein is the milk protein that turns curdled milk into glue.
- ▸Once dry, the paint is rock-hard and waterproof.
- ▸Goes onto wood, plaster, paper — anything that isn't shiny.
Steps
- 01
Warm milk gently, stir in vinegar; the milk will curdle.
- 02
Strain through cloth — keep the solid curds, discard the whey.
- 03
Rinse curds and squeeze dry.
- 04
In a bowl, mash curds with the lime — they will dissolve into a smooth, sticky binder.
- 05
Stir in pigment paste (pigment + a little water) to the consistency you want.
Materials4
- — 500 ml skim milk
- — 2 tbsp white vinegar
- — 1/2 tsp slaked lime (calcium hydroxide) or baking soda
- — Dry pigment
Safety
Involves caustics, acids, or open flame. Full PPE and trained supervision recommended.
- Caustic alkali — burns skin, eyes, lungs
- Acidic / corrosive etchant
- Airborne dust — respiratory irritant
- ☐Wear chemical splash goggles and nitrile gloves
- ☐Add alkali to water, never water to alkali
- ☐Keep vinegar nearby to neutralize spills
- ☐Wear goggles, apron, and acid-resistant gloves
- ☐Always pour acid into water, not the reverse
- ☐Neutralize and dispose per local hazardous-waste rules
- ☐Wear an N95 / FFP2 mask when handling dry powders
- ☐Mix in a tray to contain dust; wipe surfaces wet
- ☐Work in a ventilated area; keep food and drink out of the studio
- ☐Read each material's safety data sheet (SDS) before starting
- ☐Have water, soap, and a first-aid kit accessible
Heuristic guidance derived from listed materials. Always consult each material's safety data sheet (SDS) and a qualified instructor before attempting.
Notes
Once dry, casein is water-resistant and extremely durable. Use within a day — it spoils fast.