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Cheap pigments for plaster  RSS feed

 
Thomas Sommer
Posts: 13
Location: China
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Hi Dan, and all natural builders

We're in rural China and don't have regular access to pigments used for coloring cement. The mineral pigments we have found are very much out of our price range. Could you recommend other sources of natural pigments?

I'm aware adding lime or different colored clays can influence the resultant color, but what about plant based pigments usually used in natural dye?

Thanks
Thomas
 
Kim Bozarth
Posts: 23
Location: Nevada
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If you like yellow you can use turmeric! A little goes a long way and depending on the clay you start with can give you a really nice color. I've also used cinnamon.
 
Dan Chiras
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Hi Thomas...I have never found cheap pigments for natural plaster other than concrete pigments. They can be purchased in the states from pottery suppliers. Some are pretty inexpensive. My problem is that the number of options is pretty limited. The best pigments I've found are pretty pricey. I purchase them from a supplier in Denver who gets them from American Clay. I will make my own finish plaster and buy the pigment from this company. I think it is Verde Paints or something like that. Sorry, it's late and I can't remember the name.

Colored clay can be used to pigment finish coats, but you have to consider the colored clay as part of your mix...in other words, remember that it is clay. If you are making a plaster from fine silica sand and clay, the clay pigment adds to the clay content of your mix...so you will need to use a little more sand.

I typically mix one part of clay to one or two parts of fine-grained silica sand. I tried something different last summer and was really impressed with the result. I made a finish plaster with one part of powdered silica sand to one part of powdered clay. It worked really nicely. The stuff troweled on easily and looks terrific. All readers of this might try experimenting with this mix. The ratio of sand to powdered clay might be a little different, but I think you will find that it works very nicely.
 
Erica Wisner
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Location: Okanogan Highlands, Washington
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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
 
Thomas Sommer
Posts: 13
Location: China
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Thanks Kim, Dan and Erica for the good info.

We'll be experimenting with rust, soot and chalk in our current projects. I've looked into growing turmeric as a perennial before but found our climate to be much too cold. If we could grow it as an annual it might be worth looking into as a pigment.

Does anyone use other plant based dyes for coloring plaster or paint? We have lots of pokeberry growing on the mountain and I have been reading about fermenting the berries for fade resistant brown colored ink. Has anyone tried this as a plaster pigment, or should we experiment next fall and reply with the results?

 
Judith Browning
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Location: Arkansas Ozarks zone 7 alluvial,black,deep loam/clay with few rocks, wonderful creek bottom!
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Thomas Sommer wrote:Thanks Kim, Dan and Erica for the good info.

We'll be experimenting with rust, soot and chalk in our current projects. I've looked into growing turmeric as a perennial before but found our climate to be much too cold. If we could grow it as an annual it might be worth looking into as a pigment.

Does anyone use other plant based dyes for coloring plaster or paint? We have lots of pokeberry growing on the mountain and I have been reading about fermenting the berries for fade resistant brown colored ink. Has anyone tried this as a plaster pigment, or should we experiment next fall and reply with the results?



You might want to research using madder...'rubia tinctorum' the roots are a source of very beautiful reds. it is fairly easy to grow if you have fresh seed or can find someone to share roots. I found very good seed from Horizon Herbs...fresh and great germination. It is considered an 'invasive' and not sold to some areas.
It has a large history as a dye plant...for fiber, violins, oil paint. It takes three years to begin harvesting roots but is so worth the wait. I don't know about as a dye for plaster, though....it seems like it should work if you reduce to pure pigment as in 'LAKE' PIGMENTS for oil paint.

...I have used poke for an ink and an attempt at fabric dye...it is disappointing for such a beautifully colored fruit...it is not at all light fast and becomes off towards a brownish color, at least in my experience.
 
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