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Mineral Pigment Processing: Health and Safety Tips

Ruth Siddall16 September 2020

As a geologist, I get asked lots of questions about the safety aspects of preparing mineral pigments and paints, so I thought I’d write down what I have learned during my career as a geologist and answer some of the questions I’m frequently asked. Are mineral and earth pigments safe? Well, the answer is yes and no. Most materials are safe to use if you take the correct precautions on collecting, processing, storing and using them. The more you learn about the materials, the more you understand the risks. The same goes for all artists’ materials, including glues, resins, jesmonite, white spirit and so on. For stuff you buy over the counter, material safety data sheets are readily available. Obviously, this is not the case for stuff you might collect in the great outdoors. Here are some tips, and my personal feelings, about the risks of working with rocks and minerals and how to mitigate them. This applies to people working in sculpture and pottery as well as pigment processing. If you’re grinding rocks and minerals for pigments occasionally and in small amounts, there’s very little risk. However, if this is something you’re doing everyday, you need to take some precautions to protect your health. All dusty materials can affect your respiratory system, but some materials have more damaging effects than others.

What I’m writing here applies to rocks, minerals and biominerals (shells, bone) that you might find in your environment and are regularly used to make pigments or for carving. These tips do not apply to toxic or chemical waste products (which should be avoided at all cost), plants or animal materials (including dyes and lake pigments), or processed products like metals, plastics, resins and glass. Many of you will already know this and take precautions when preparing mineral pigments. However a lot of people are find this activity for the first time. So here we go …

Learn about natural materials and their risks …
Try to learn what you can about what naturally occurring materials are made up of. You can google most things and check their chemical formula. Also look at hazard sheets for similar materials sold by paint manufacturers. Find out what is dangerous and what is not and collect accordingly. Wash your material when you get it home to remove any dirt or potentially hazardous biological material. If you are working with relatively small amounts of these materials every now and again, there is no major hazard associated with them.

It’s all about what you wear …
I’m a lab and field scientist by background and health and safety is drummed into you ALL THE TIME in these environments. There is a reason why you never see scientists in labs wearing, shorts, T-shirts and sandals. In labs, we wear lab coats, face-masks and goggles. We don’t wear this stuff just to protect our clothes or to stop stuff splashing our eyes, we wear it to protect our skin, eyes and internal organs from ingesting dangerous materials. If you’re going to prepare pigments, think like a scientist and dress appropriately. Cover your skin, eyes and mouth. If you are really worried, wear ear-defenders too. As a field geologist we had to wear goggles when we were hammering or crushing rocks. These are proper goggles with a seal round your face (like a snorkel mask but without a breakable glass front) so nothing can get in. A visor won’t stop dust getting into your eyes. This is all really obvious stuff. If you do this, your risk of ingesting or absorbing dangerous substances will be really, really low.

My friend Jim using a rock saw and wearing appropriate safety kit. This is a water saw so there’s no dust, which is why he doesn’t have a mask on. A constant spray of pressurised water washes dust down into the trough. This water has to be disposed of via a sediment trap (and not straight into the drains).

Tidy up and wash-up …
Clean up your work-space thoroughly when you have finished working. Use a vacuum cleaner to get rid of dust. Oh, and have a shower when you’re done! Wash your hair while you’re at it. Don’t eat or prepare food until you’re clean. Really straightforward stuff, but again it hugely reduces risk.

If you are doing this a lot, invest in decent processing kit …
If you are making pigments commercially, and therefore grinding stuff every day, you should probably invest in some proper kit, i.e. mechanical grinders such as disc mills or ball mills AND a proper dust extraction set up.
When I was a grad student, I earned a bit of extra pocket money by rock crushing (as well as crushing tonnes of my research project rocks). You need to crush rocks to a fine powder to study geochemistry and geochronology. I would spend days, weeks doing this. It is quite a slow process. We had a purpose built space with different machines which gradually reduced the grainsize of the rock, starting with a sledgehammer and ending with a disk mill. Also we had a huge set of extractor fans to remove all the dusts. These were like enormous vacuum cleaners which we could move and direct so they were right over the source of the dust and suck it all up. I’ve done a lot of this and I was well aware that the more you do, the more you’re at risk. I still use the lab for grinding if I need to make a lot of pigment. So if you just grind up a handful of ochre once a year, there’s little to worry about (but wear a mask), but if you’re grinding pigments and making paints regularly, you should take precautions and ideally do it in lab conditions where there is protective equipment. Dust is the enemy!

What scares me?
There are a few things that I would not normally grind by hand at home, because they produce specific hazards. Obviously radioactive minerals are a no go. This is not a huge issue with modern pigments but can be an issue when working with some 19th Century materials.

Silicosis is a horrible respiratory disease which comes from long exposure to silica dust. It cannot be cured and it is cumulative; the more silica dust you breathe in, the worse it gets. Silicosis is a killer among workers in granite quarries who have constant exposure, but potters are also at high risk. Breathing in the silica dust scars the lungs and leads to breathing difficulties. Generally, it is best to try and avoid breathing it in. The great majority of rocks on our planets are silicates (sandstones, granites, basalts, schists, slates etc), basically anything that’s not a limestone. I would not advise grinding silicates unless you have proper rock crushing and grinding facilities including extractor fans, as described above. I admit that I have crushed slates and shales by hand, but they’re at the softer end of this spectrum, and I’ve been masked up, etc. But I still regret it. Silicate rocks and minerals includes lapis lazuli and clay-rich rocks. Get it crushed in a proper lab with dust extractors. It scares me when I see people crushing basalt, sandstones, granite etc. Also most silicate minerals lose their colour when finely ground, so it’s a bit of a waste of time. The only silicate mineral worth grinding (in my opinion) is lazurite (the blue mineral in lapis lazuli), but again this should be done in the presence of an extractor fan.

Serpentinites are also silicates but in addition they contain asbestos, so just leave them well alone. Soft, attractive and colourful though these rocks are, I would never grind them, and I don’t even like sampling them at outcrop. The lung cancer caused by asbestos, mesothelioma, is not necessarily dose related. It can be caused by just one, unlucky breath.

A polished slab of serpentinite, a rock predominantly formed of the serpentine group minerals, which can be asbestiform. Serpentinites are very variable in appearance, varying in colour from black, to grey, green, bright red and yellow. They often have a distinctive ‘snake-skin’ like texture and feel soft and soapy to the touch.

What’s an ‘acceptable’ risk?
Some pigment minerals are known to be toxic because they contain heavy metals, copper, cadmium, arsenic, mercury, lead etc. Some of these are super-poisonous, but they are also very important as pigments both art historically and in the present day. As this is what I research, needs must. Heavy metals can build up in the body, so this is dose related – and can do a lot of harm. Some can kill you. You can ingest them through breathing in dust or getting it in your eyes and ears, and some you can absorb through your skin. This risk can be massively reduced by not grinding or working with these materials wearing a vest top! Cover up, mask up, wear goggles. I would never grind large amounts of these minerals. Even though I’m a pretty good mineralogist so I know what I’m looking at, one cannot be sure of precisely what is present in a mineral sample. The unknown unknowns are a problem, microminerals or inclusions of poisonous stuff, or similar looking phases that might be hidden with a mineral. The worst of these minerals are the arsenic and mercury sulphides; orpiment, realgar, pararealgar, conichalcite, cinnabar, metacinnabar etc. and synthetic pigment equivalents like vermillion. Many of the worse pigment poisoners, like Scheele’s Green, Hooker’s Green and some varieties of cobalt violets (i.e. cobalt arsenate) are now banned. These materials are very bad for you, large enough doses can kill. They are also dangerous because they begin to break down thermally and at low temperatures, i.e. not much above room temperature and start releasing straight arsenic. Also, if you have samples of these minerals, don’t have them on an open display shelf, keep them in a sealed bag or box. Keep them away from sunny windowsills! When preparing them as pigments, do so in small amounts, and make sure your skin, mouth and eyes are covered. It’s probably a good idea to wear disposable gloves too. Make sure you was hands and face afterwards, and certainly before eating.

Cadmium pigments and lead pigments are a big risk in the same way, but at least you buy these in powdered form, so there is not the grinding hazard.

Copper minerals, i.e. malachite, azurite, atacamite, chrysocolla, conichalcite (a copper arsenate, so a double whammy, and it looks just like malachite) and lead minerals (to be honest rarely collected as minerals but the main ones are crocoite, galena etc.) are also poisonous, but you would need a much bigger dose to kill you, but they can have lasting damaging effects. Again, the rule is to try to avoid making pigments from these minerals unless you’re in a lab environment, and if you are doing this in your studio, do so in small amounts, cover up and wash afterwards.

The good news is, that once incorporated into a binder, these pigments are much safer, but care needs taking, especially with the very thermally unstable arsenic sulphides.

Something to be aware of is flushing pigments and paints made from these minerals down the sink. Try and avoid doing this!

Above: Conichalcite, a calcium copper arsenate hydrate. Quite a poisonous mineral, as minerals go! This is the nearest natural equivalent to the copper arsenate pigments which were really popular in the late 19th Century.

What’s OK (assuming above precautions are taken)?
Limestones and other carbonate rocks (these don’t contain silica, so no silicosis risk)

Biominerals (shells, coral, cuttlefish bone, bone etc) are carbonates or phosphates and don’t present any major risk, although they can absorb heavy metals during the lifetime of the organism, so this is something to be aware of. Boiling these materials in water before processing, for at least 10 minutes, should kill off any biological hazards and reduce the smelliness!

Iron-ochres and earths – however many of these do also contain clays, which are silicates and they can contain other heavy metal compounds. The purer the iron ochre, the safer it is. You’ve already got a lot of iron in your body, so you need to absorb an awful lot more to make yourself poorly from it. Nevertheless, iron poisoning is a thing. Breathing in a few particles won’t do you much harm, but it’s always best to avoid it. Again, this is more of an issue if you’re processing ochres on an industrial scale but cover up to avoid ingestion of materials and you’ll be OK. However, as dust is the enemy, even if these are not going to poison you, you need to avoid the dust, they can cause respiratory problems.

NB: Not all ochres are iron-rich. Other metals (cobalt, nickel, aluminum) can also form ochreous deposits.

 

FAQs – I’m happy to add to these!

What about heavy minerals and pollution in the environment?
This is an issue. But again it’s about reducing the chances of your body absorbing this stuff. The are trace amounts of heavy minerals that are pollutants in shells, bones, cuttlefish bone etc., so treat them with care and cover up whilst you are processing them. Clays can hoover up pollution, so take care if you’re collecting clays from industrial or former industrial areas. If you wash them and they smell funny or you get that oily, iridescent film on the water, then to be honest, I would leave it at that and dump them. They can contain some really nasty stuff, like benzene (this is a problem with the London clay in some Victorian industrial areas in London). Brightly coloured mine waste products should be treated with care too. The orange ochre mineral ferrihydrite that you see in streams is usually OK but check what was being mined there as these deposits can also contain arsenic and other horrors. Anything else, personally I’d leave well alone. It is waste for a reason and also sorts of nasty chemicals were used to process it.

Are you saying that I really should be only processing pigments in a lab environment?
No, not at all. Making these things at home is good fun. You just need to follow the basic safety advice; wear a mask and ideally eye mask, wear long sleeves and clean-up yourself and your space afterwards.

I’m still anxious about the risks some of these materials pose and feel I don’t know enough about them. Should I use them?
The simple answer to this question is no. If you don’t feel comfortable using a certain material then just don’t.

I’m getting conflicting advice about the risks of working with a certain rock, mineral or shell. How do I find out what the truth is?
Again, if this is making you uncomfortable, simply don’t use that material. But remember, the hazard is caused by getting this stuff into your body. If you do everything you can to avoid that, then you will reduce the risk. Try to rely on scientific sources rather than social media and hearsay to get more information.

Should I just completely avoid using seriously toxic mineral pigments like orpiment and vermillion?
No, but you should learn about them first and understand what the risks are. There’s lots of safety info out there. These minerals/pigments need handling with care. As I keep saying, you just do everything you can to avoid this stuff getting into your body. I wear gloves for handling orpiment. However, if you have no need to use these pigments they can be easily avoided. You can buy safe modern paints which have similar colours and properties.

Is it safe to teach kids pigment processing techniques?
It’s not safe to use the toxic mineral pigments mentioned above (copper, arsenic, lead, cadmium, mercury etc. based pigments), but processing ochres and chalks will be fine and good fun; no more risky than making mud pies. Levigating clays and ochres in water is pretty safe too. Make sure they’re supervised, old enough not to know not to eat it and make sure they’re wearing a mask if they’re working in dusty environments.

Many minerals have therapeutic properties, won’t this help protect me?
No, they don’t and no, it won’t. Sorry. In fact many minerals pose risks as described above and can be very harmful. Breathing in their dust or inserting them into your body can be really dangerous. Also the mineral trade to produce therapy crystals is really, really, really unethical and exploitative a lot of the time … but that’s another story.

A Colour A Day: Week 25

Ruth Siddall13 September 2020

A Colour A Day: Week 25. 7th-13th September

Jo Volley writes…A method for making shell gold.

Grind either skewings or leaf gold with a small amount of clear honey into a paste using a muller and slab. Work the muller slowly in a figure of eight until you have the mixture spread out thinly on the slab, gather up and begin grinding again. Continue this process for approx. 15 minutes or until you have broken down the gold into fine particles. Place the mixture into a glass and fill with hot water to flush out the honey.

When the gold has settled to the bottom of the glass decant the water.
Repeat approx. 5 or 6 times until all the honey is removed. De-ionised or distilled water is recommended for the last 2 stages. Allow the gold pigment to dry. Bind with gum Arabic and store the gold paint in a shell.

All pigments are bound in gum Arabic on W&N watercolour paper.

First column left to right: Four gold pigments gifted by the artist, Lisa Milroy, collected on her travels in China.

Second column top to bottom:
Schmincke pale gold
Jo Volley’s shell gold
Schmincke rich pale gold

A Colour A Day: Week 24

Ruth Siddall6 September 2020

A Colour A Day: Week 24. 31st August – 6th September

Jo Volley writes…

This week we pay homage to the maillot jaune of the Tour de France with seven historic yellow pigments and celebrate Adam Yates, English cyclist, wearing it for the first time. The maillot jaune was adopted in 1919 by Henri Desgrange, director of the tour, to distinguish the leader of the race more easily within the peloton. Desgrange was also editor of the sports paper L’Auto which funded the tour and printed on yellow paper. To quote Jens Voigt, who wore the maillot jaune for a day during the 2001 tour, ‘Yellow is a beautiful colour, no?
All pigments are bound in gum Arabic on W&N watercolour paper and read from left to right:

Gamboge

Lead tin yellow

Orpiment

Alizarin yellow

Naples yellow

Indian yellow

Aureolin

In memory of Tommy Simpson, the first British cyclist to wear the yellow jersey.
30 November 1937, Haswell – 30 July 1967, Mount Ventoux.

A Colour A Day: Week 23

Ruth Siddall29 August 2020

A Colour A Day Week 23. 24th August – 30th August.

Jo Volley writes…

This week we celebrate Goethe’s 271st birthday, 28th August, with earth pigments from Cyprus collected and processed by Ruth Siddall who says of them …

Cyprus is an island long associated with the production of pigments. These are by-products of the copper mining that has been active since the Bronze Age when Cyprus was the main supplier of copper ingots in the eastern Mediterranean region. But it was not copper-based pigments that were in abundance, it was the iron and manganese-rich ochres and umbers which were typical of Cyprus as well as the celadonite-rich green earth deposits. The Cypriot umber is a true umber in the geological sense having formed at a mid-ocean ridge plate tectonic boundary. In fact this is the environment of deposition of all of Cyprus’s ores and pigments. They originally formed in deep ocean waters, superheated by volcanic activity and then this slab of oceanic rock, ores and all, was emplaced onto the Eurasian continent during the construction of the Alpine mountain chain. The ochres formed by the weathering of the ores both before and after this emplacement onto dry land. Such a geological environment is uncommon, and Cyprus is by far the biggest example of these processes on Earth. A unique island for pigment formation.’

All pigments are bound in gum Arabic on W&N watercolour paper and read;

Left hand column from top to bottom:
Yellow Ochre, Sia Mine, Cyprus
Jarosite Yellow Ochre, Sia Mine, Cyprus
Burnt Umber, Margi, Cyprus

Middle column:
Red Ochre, Sia Mine, Cyprus

Right hand column from top to bottom:
Raw Umber, Margi, Cyprus
Terra Verte, Cyprus
Brown Ochre, Sia Mine, Cyprus

A Colour A Day: Week 21

Ruth Siddall16 August 2020

A Colour A Day Week 21. 10th-16th August

Jo Volley writes….

Extracts from Matisse on Art Jack D Flam 1973. On the occasion of an exhibition at the Gallery Maeght, December 1949 the title of which was Black is a Colour. Henri Matisse’s remarks were recorded by M. Maeght.

Before, when I didn’t know what to put down, I put down black. Black is a force: I depend on black to simplify the construction. Now I have given up all blacks*The use of black as a colour in the same way as the other colours – yellow, blue or red – is not a new thing. The Orientals made use of black as a colour, notably the Japanese in their prints. Closer to us, I recall a painting by Manet in which the velvet jacket of a young man with a straw hat is painted in a blunt and lucid black. In the portrait of Zacharie Astruc by Manet, a new velvet jacket is also expressed by a blunt luminous black. Doesn’t my painting of the Marocains use a grand black which is as luminous as the other colours in the painting? Like all evolution, that of black in painting has been made in jumps. But since the Impressionists it seems to have made continuous progress, taking a more and more important part in colour orchestration, comparable to that of the double-bass as a solo instrument. 

*Matisse does not mean he has given up the use of black, but that he no longer used it merely for linear construction as in his earlier works. Actually, at this time Matisse was making a use of black as a colour instead of an element of linear construction.

From left to right

  1. Jet – W&N Designers gouache
  2. Perylene – W&N Designers gouache
  3. Lamp – W&N Designers gouache
  4. Blue Black – W&N Calligraphy ink
  5. Mars – W&N Designers gouache
  6. Ivory – W&N Designers gouache
  7. Noir Intense – Lefranc Bourgeois Linel gouache

A Colour A Day: Week 20

Ruth Siddall9 August 2020

A Colour A Day – Week 20. 3rd – 9th August

Jo Volley writes…
This week’s colours are more earths, gifted by Steven Patterson, Chief Executive Officer, Derivan, Australian artist materials manufacturer, from their Matisse Structure Origins Range. To accompany them please listen to Mahler’s Das Lied von der Erde;

The earth breathes, in full rest and sleep.
All longing now becomes a dream.

Each colour is painted out in 3 layers on W&N watercolour paper and read from left to right:

1. Armenian Gugark Cherry
2. Morrocan Yellow Oxide
3. Armenian Lori Red Light
4. Armenian Tavush Trans Green
5. Armenian Lori Violet Light
6. Armenian Kotayk Ochre
7. Armenian Bole

A Colour A Day: Week 17

Ruth Siddall19 July 2020

A Colour A Day.  Week 17: 13-19 July

Jo Volley writes…

Over the last week I have had the privilege to work with 7 colours produced and sent to me by Ruth Siddall.  To receive these little packets of pigments through the post and work them into paint has been a pure delight.    

Ruth says of them. “These colours are all based on lake pigments made from American plants and an insect, the cochineal beetle. Three are wood dyes (logwood, brazilwood and osage orange), Aztec marigold was made from dried flowers, the avocado lake was made from a dye extracted from the stones of the fruit. Annatto (or achiote, achiotl) is a spice made from seeds. The latter was used as a ink in historical Mexican painting, and also as food colouring and a cosmetic.”    

All are bound in gum arabic on W&N watercolour paper and read from left to right.

Osage Orange, Maclura pomifera
Annatto, Bixa orellana
Cochineal, Dactylopius coccus
Logwood, Haematoxylum campechianum
Brazilwood, Caesalpina echinata
Aztec Marigold, Tagetes erecta
Avocado, Persea americana

A Colour A Day: Week 16

Ruth Siddall12 July 2020

A Colour A Day Week 16: 6th -12th July

Jo Volley writes…

This week’s A Colour A Day is inspired by Robert Rauschenberg’s White Painting (seven panel), 1952.

Of the series, his friend the composer, John Cage wrote:

To Whom / No subject / No image / No taste / No object / No beauty / No message / No talent /
No technique (no why) / No idea / No intention / No art / No object / No feeling / No black / No
white (no and) / After careful consideration, I have come to the conclusion that there is nothing in
these paintings that could not be changed, that they can be seen in any light and are not
destroyed by the action of shadows. / Hallelujah! the blind can see again; the water’s fine.

Read from left to right are 7 white pigments bound in gum arabic on W&N watercolour paper.

  1. Lead
  2. Zirkonium silicate
  3. Egg Shell
  4. Zinc
  5. White Earth
  6. Fluorescent white
  7. Titanium

A Colour A Day: Week 15

Ruth Siddall5 July 2020

A Colour A Day: Week, 15. 29th June – 5th July

Jo Volley writes…….

In spring 2017, Nisar Hossain, Dean of the Fine Art Faculty, University of Dhaka, Bangladesh, Artist and specialist on Contemporary Painting and Folk Painting of Bangladesh, led a contemporary installation  workshop at the Slade based on traditional Folk Art of Bangladesh.  He also gave  a public lecture at the Whitechapel Gallery The heritage of ritualistic folk painting and the traditional painter communities of Bangladesh as part of the Inspire exchange project between the Slade School of Fine Art and the University of Dhaka Faculty of Fine Art, Bangladesh funded by the British Council.

Links to various workshops throughout the Inspire project

Here are 7 of the colours Nisar generously donated to the Material Research Project pigment library, written in Bangla, as he gave me. Each are bound in gum Arabic on W&N watercolour paper and read from left to right.

  1. Hāra pathar
  2. Haritāl
  3. Sindura
  4. Bhusha kali
  5. Hingula
  6. Elamati
  7. Nīl

 

A Colour A Day: Week 14

Ruth Siddall28 June 2020

A Colour A Day week 14; 22nd-28th June

Jo Volley writes …
I am currently working on a timeline of Van Gogh’s colours for the Van Gogh House in London. In a letter to Theo dated 8th April 1888, Arles, he writes;

‘My Dear Theo, Am obliged to write to you as I’m sending you an order for colours which, if you place with Tasset & Lhote, rue Fontaine, you’ll do well – since they know me – to tell them that I expect a discount at least equivalent to the cost of the carriage…‘ He continues with a list of instructions for colours, canvas and carriage then writes…