China has a long
art history, and there may be historic pigments worth looking up through a
local university.
- Many cheap tempera paints ("poster paint") will work fine with clay plasters and paints, though some may lose color or change colors if exposed to alkaline materials like lime. These colors may be fugitive - they can fade with exposure to light, or just over time.
For more permanent colors, from cheap materials:
- Fine soot is the black pigment used in "India" ink (Chinese traditional ink), though not many people want to tint their walls grey-black. But a little grey, and a little yellow ochre, can give a surprisingly greenish effect. (Useful for setting off more intense colors, and for murals, e.g. painting bamboo in greenish and yellowish tones. Kind of a sickly effect if it's used for whole rooms). You could make it by collecting soot from cooking fires or chimneys, I usually save mine when I vacuum out the stove annually. Or by grinding charcoal, though that's a greyer effect and might be better for plasters than paints.
Chemical compatibility: It
should be pretty neutral in small quantities for most natural plaster mixes. If there's creosote, tar, or pine pitch present, it could have a slight binding effect, or create odd smells, toxicity, flammability. Not terribly dangerous unless you used
enough to tint the plaster or paint very dark black. This type of pigment,
carbon blacks, have a reputation for keeping linseed oil from setting completely. Graphite and vine charcoal are other variations on this pigment.
- White: Clays, chalks, lime (several coats). Could possibly get a very white
ash from burning clay-coated recycled paper; white clay is used a lot as a size for color printing. Some people get paper delivered by signing up for junk-mail lists, though color printing sometimes adds other minerals (copper, etc) that will turn the resulting ash less white. Properties: Alkaline - could cause some other pigments to change color. Turmeric goes from yellower to browner under various acid / alkaline conditions.
- Warm Ochres: You can soak rusty metal to produce your own ochres. A little salt or acid accelerates the corrosion process.
- Iron black is what coats cast-iron; not sure how to make it in quantity.
- Bog iron is yellowish - formed in oxygen-poor, cool conditions. Soaking iron in deep
water (e.g. a barrel) can result in yellowish pigment deposits on the bottom.
- Red ochre forms in hotter, oxygenated conditions. I've seen boring yellowish clays or plain yellow-grey rocks turn orange or pink like rosy bricks when heated in an intense fire.
Brick ochres: I have also had great fun with small kids grinding soft red bricks down into pigment - any brick that can be used as 'sidewalk chalk' can be ground down on a concrete surface and sifted as a plaster additive. Brick grog will act more like sand in your plaster.
- Good, non-toxic, bright blues and greens are rare. This is where I spend my money on pigments: a good, deep, ultramarine-type blue from American Clay or Ochres and Oxides can be mixed with white to make lighter blues. I don't know how to make them, so unless you find a local source you might be out of luck.
Borax or 'blueing' (laundry additives) might be locally available to whiten or lighten any dingy blue-ish or white surfaces.
Copper (verdigris) makes a good green-blue, can be oxidized like iron, or copper or nickel ores can sometimes be found locally. Slightly toxic. Copper sulfate is too water-soluble to be useful as pigment or dye. Could potentially dye the fibers for the plaster with a commercial dye like indigo or woad, but this might not come through in the result.
I might also look into getting a big shipment of blue chalk - e.g. the contractors' marking chalks, or the powdered refills for chalk lines.
Getting the most out of your (limited) local palette:
- For any expensive pigment you can't afford in quantities, don't make tinted plasters, or tint the plaster as a suitable base with something cheaper.
E.g. do a white or light-grey wall, and then add a very thin wash or paint of blue / yellow pigment. This makes the color brighter, and the pigment go further. However, it's harder to do evenly, and it will also show dings and scratches more than a solid, tinted plaster.
- The finer you can grind a pigment, the further it goes. Extreme grinding can slightly lighten the color of a pigment, because smaller particles reflect more light ("glare") instead of just the color itself.
- Suspending it in oil, or coating with an oil or varnish, will darken the pigment color closer to its wet hue.
- If tinting a plaster, remember that the other materials in the plaster count as pigment too. Clay, lime, sand - it's very hard to make a plaster white if using grey or red sand, in fact a white plaster with black sand is the ubiquitous grey color of Portland cement / concrete. Experiment with very small batches - some pigments darken plaster surprisingly quickly, and others disappear into the white or brown no matter how much you add.
- Color theory is useful too.
- Use compatible base colors.
No amount of red pigment will turn green plaster pink; the most you'll achieve is a brownish hue. Fresh animal dung sometimes gives a greenish cast to plasters, though I'm told this mellows over time; some colors of sand will add to the effect, and yellow clays can also color plasters quite intensely. A yellow or warm orange will be a lot easier to achieve over this greenish effect than a pink or purple.
- Likewise, if you are working with a bluish-white or greyish local clay, adding red tints often results in the most disgusting corpse-pink, rather than a nice warm color. Even warming up those blue-grey clays with yellows can take a lot of pigment. If you want a warm color, start with a warm base, like yellowish or orangeish local clays. If you want a cool color, like a cool grey or bluish, go for the cool-color clays or a neutral base.
- White lime plasters with white sand are easier to paint over in most colors, but can soak up a lot of pigment if you're trying to tint the plaster itself.
- Contrast: If you want to make natural tints appear brighter, e.g. "red" trim from a dingy barn-red brick pigment, use a contrasting color nearby.
In this case, a white plaster made slightly greenish by inclusion of animal dung or plant matter (I suspect thistles might make a good green dye, but haven't tried it yet) would set off red trim and make it appear brighter. So would a greenish "brown" plaster made with a brown local clay, and inclusion of some black or grey to tint the brown cooler. This greenish grey-yellow-ochre background tint makes red or orange trim details stand out and look brighter, almost garish sometimes.
Yellow-oranges set off blues and purples, and vice-versa. Blues and purples are rare, but a small (expensive) blue detail around windows can look stunning against a yellowish wall.
Hope that helps!
-Erica W
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