Last time I talked about making milk paint gesso from fresh or reconstituted milk. Works great. I even did a batch where I added baby powder as filler, and I have to say I’m impressed. Though there’s a lingering clean bottom scent on the dry boards, which is kind of odd.
But there’s another way to make milk paint. It’s an old and revered type of homemade paint that utilizes a substance in milk called casein. You can buy dry casein or make your own, and though I haven’t used the dry stuff, I understand it functions a little like egg in tempera paint—the pigment is suspended in the fat globules, giving the paint a deep, jewel-like clarity.
When I went looking for milk paint recipes, the first one I saw was on the Martha Stewart site and I admit, this was not a turn-on. Back to old 1870 for me. But when I finally decided to contrast the two types of milk paint, fresh vs. curdled, I went back to Martha and saw a very interesting tip in the comments about adding borax to smooth out the curds.
The recipe I ended up using was from Earth Pigments which is a wonderful site and sells all kinds of natural pigments and basic supplies. The version of the recipe I give here is for a smaller amount, though I recommend you go to Earth Pigments and spend some time with their recipes.
1/2 gallon milk
1 cup white vinegar
Have the milk at room temperature before you add the vinegar. Once you add the vinegar don’t stir it anymore because the curds are already forming. Let the mixture sit in a warm place overnight. The next day, line a colander with cheesecloth (that’s what it’s for) and place it in your sink or over a large bowl. Pour the milk and vinegar mixture through the colander, thus separating the curds from the whey. I don’t know what to do with whey but it might be good for something. I just let mine go.
Next run some water very gently over the curds to wash away the vinegar. Put the dripping wet curds in a large bowl or gesso container. In a separate container, add:
½ cup hydrated lime
¾ cup water
Add water to the lime until saturated. You should be able to make a creamy paste, though I use garden lime which has to be sifted to remove larger chunks of rock and didn’t get anywhere near creamy. This milk paint recipe seems to require a very fine grade of lime, which you might want to buy specially. The 1870 milk paint recipe isn’t nearly as finicky.
Add the lime/water combination to the curds and stir. The curds should start to break down and become smooth. If this doesn’t happen, do what Martha Stewart’s commenter suggests and add:
½ teaspoon of borax
When the curds are smooth and the paint resembles pancake batter, add:
1-2 tablespoons of pigment
3-4 cups of filler such as chalk, gypsum, even baby powder.
Blend until it is smooth and luscious, and add more filler until you get the consistency you want. Use a gesso brush to paint your boards, making even left to right strokes. Allow to dry overnight, then add another coat, if desired, turning the board 90 degrees clockwise and using left to right brush strokes (this time in another direction). When the gesso is thoroughly dry, sand it until silky.
My version of casein milk paint gesso still had a few lumpy curds. Next time I will probably run it through the food processor. But when fully dry, the gesso was solid and tight and easy to sand. I have to say I still prefer the 1870 version for sheer simplicity, but this paint is nice and if I ever want to distress any furniture, I know where to go. Here’s a photo of casein gesso still wet: