How to make pigment from azurite and malachite (part 1)

This blogpost is the first of two parts from one of my handouts “How to make pigment and paint from azurite and malachite” made for my class on how to make pigments held at Cudgel Wars in Aarnimetsä AS LIII. You can read about how to make pigment from malachite in part 2!

How to make pigment and paint from azurite and malachite

written by Silwa af Swaneholm

About the stones
The two cousins azurite and malachite are pigments that were often found on the medieval palette and used in manuscripts. They are both copper ore stones and while azurite is blue the malachite is green. According to Thompson malachite is a changed form of azurite and contains “a higher proportion of combined water” (The materials and techniques of medieval painting. p.161).

Azurite can be blue but also comes in shades that are more greenish, that probably means that the shades with more green has more malachite in them. Malachite can have many shades from blue-green to green-blue and I guess that depends on the amount of azurite remaining in the malachite. You can buy azurite stones which you can clearly see have pieces of malachite in it. I prefer to buy azurite clusters that seem to have very little malachite in them and then malachite stones in various shades of green.

Azurite

Azurite was often called azure. From the beginning the word comes from lajoard, a persian word for blue. The borrowed word became lazurium in latin and then azurium. Azure is the word most often applied to all blue colours such as indigo, wood and so on. The pigment made from azurite was sometimes called citramarine azure, german azure, spanish blue, lombard blue or “our” blue (when the author referring to the colour lived where the azurite could be found (Germany, Spain, Hungary or Italy), the azurite colour was in short named after where it could be found. Azurite was usually found in silver mines.

Azurite turns black when heated red-hot and lapis lazuli does not turn black when treated this way. Azurite sometimes looks very similar to lapis lazuli but since lapis is much more expensive this was good to know and a way to find out what stones it was. Azurite also turns black when mixed with strong alkalines and from some varnishes. Many colours that appear black in paintings today where originally blue that turned black because of the varnish.

To make pigment out of azurite you need to grind the stone to a powder. Too much grinding can make the pigment pale but if it is not ground enough the pigment will be sandy and too gritty to be used in paint. The pigment was ground, washed and then separated to become different shades of blue. Separating was done with mixes of water, soap, gum arabic and water. First the pigment was ground with soap and then boiled in water. When doing this the sand in the azurite would go to the bottom while the azurite floats together with the soap. After this the pigment was ground with gum arabic and washed in weak lye water solution. The azurite particles takes a long time to settle in clear water so adding lye is a way to make it settle faster.

I tried to figure out what kind of soap that was used when cleaning the azurite. I have not found the answer yet. Most soap seemed to be made from alum and/or potash. After being washed with soap the pigment is to be cleaned with lye.Since I learned that azurite may turn black if mixed with strong alkalines I therefore decided to try sodium bicarbonate instead (also did not have lye at home). It seems to work well with this type of cleaning, at least with the stones I have tried.

Materials needed

  • Azurite
  • Safety mask and gloves
  • Mortar and pestle
  • Slab and muller
  • Jars, to rinse the pigment in
  • A flat spatula
  • Pipette
  • Something to stir the pigment with (I use grill sticks)
  • Distilled water or rain water
  • Lye (potash) or sodium bicarbonate
  • Gum arabic
  • Honey or unrefined sugar (if you want more shine to your paint)
  • Shells, or something else to store your paint in.
  • Small glass jars (if you don’t want to make paint from all your pigment).
  1. Start with beating and crushing the stone/stones in a mortar. Hold the mortar so that your hand covers as much of the opening as possible while you still should be able to beat the stones with the pestle. This way you avoid having small pieces of stone and dust everywhere. When the first crushing is done you should start grinding the pieces into a powder.

  2. Transfer the powder to the slab and start grinding it with the muller to achieve a fine powder. Remember that too much grinding can make this pigment pale but if you grind it to little it will be sandy and to gritty to be used in paint. Use small circular movements when grinding and when the pigment is spread all over the slab take the spatula and try to collect the pigment to the middle of the slab and then grind again. Repeat until all the pigment have an even size. You may might also see some malachite particles that have started to separate from the azurite.

  3. Now it is time to clean/wash the azurite. Take a jar and fill it halfway with water, add a tiny amount of sodium bicarbonate and let it dissolve in the water. When it has dissolved, carefully with help from a spatula pour the pigment from the slab into the jar. Swirl the mixture with a stick and let it settle for a short while but not to long, the water should be coloured when pouring it of the first times at least!

  4. Slowly pour the water into another jar making sure that the azurite that settled in the bottom will be left in the first jar. Continue to wash the azurite, adding water, swirl and pour, each time into a new clean jar. When you have 5-10 pourings that have settled pour of the excess water. Now it is time to choose how many shades of the azurite you want. If you want 3 then take the first 1-3 depending on how much pigment they contain and pour them together in a jar.
  5. When you have enough of pigment to make some paint it is time to pour the pigment back to the slab, add some gum arabic, powdered or dissolved in water and if you want to increase the shine on the finished color add a tiny drop of honey or a small pinch of unrefined sugar to the mixture. Time for final grinding.

  6. To see if the paint need more binder or shine to it make a small test on a piece of paper, if you are pleased with the result it is time to scroop the colour to a shell. Now the paint is done and you can either start painting with it or let it dried and use it later as watercolor.

References

The materials and techniques of medieval painting. D. Thompson. 1956, Dover publications, New york

The craftsman’s handbook, “Il libro dell’arte” Cennino d’Andrea Cennini, translated by D. Thompson. 1960/1933, Dover publications, New york

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