Friday, September 9, 2011

Health, Safety, & Copper Based Metal Clay [Copper II]

by Mary Ellin D'Agostino
Technical Advisor

This is part 3 of my ongoing series on Metal Clay Health and Safety.

In Health, Safety, & Copper Based Metal Clay [Copper I] I covered some of the issues surrounding the use of copper clays and promised to continue by discussing high level copper toxicity and inhalation. As noted in my last post, no-one has reported major illnesses relating to the use of copper metal clay. As long as you are working with moist copper based clays, the main issues are skin absorbption and ingestion of clay on your hands--so wash those hands! Some copper ingestion is vital to health, which is why you see it in vitamins. For a good general discussion, check out this Wikipedia article on copper in health.

Natural Copper. Photo from

Have you ever heard of metal fume fever? This is usually associated with inadequate ventilation and molten metals, but since it involves the inhalation of tiny (fumed) metal particles, it is a risk for the metal clay artist working with copper and bronze clays. Base metal clay workers should be aware that tin (in bronze) is the most common cause of metal fume fever, but that copper can be a culprit as well. The first symptoms of metal fume fever are a metallic/sweet taste in the mouth, upper respiratory tract irritation, nausea, and sudden thirst. The first line of treatment is to get the person into fresh air. Check out Charles Lewton Brain's articles in the Orchid Archives on metal dusts, metal fume fever and general metal safety issues.

The very tiny invisible particles of metal in metal clays can stay in the air for a very long time (days). They can also be stirred up into the air very easily after they have settled, so keeping your studio clean and dust free is a really good idea. If you do much sanding, carving, or finishing dried copper and bronze clays before firing, you really should invest in a good positive studio ventilation system--see part one of this series for a discussion of ventilation.

Now for the tricky part--just how much dust is a problem? I have researched this issue and the OSHA limits for exposure to copper dusts and mists is an average of 1 mg/m3 for an 8 hour period, which does not really mean a whole lot to me other than that having more than a little copper dust in the air for long periods of time is a problem. When the copper in the air is fume sized particles, the limit drops down to 0.1 mg/m3 for an 8 hour period. That is one-tenth the amount for mere dust! The most readable discussion I have found on this is an OSHA response to a question for clarification on how appropriate measuring of dust and fume limits. These limits were set at levels that should prevent upper respiratory tract irritation. I could point you to scads of technical articles and charts I waded through, but they pretty heavy going. Let me know if you want more references. If anyone requests, I can do some further research on how a metal clay artisan could go about measuring the levels of dust, mists, and fumes in their studio air. So let me know.

Be aware that severe copper toxicity can even result in death, so pay attention to any initial symptoms and take care of them. Use wet wipes to clean up copper and bronze dust. Use a HEPA filter and vacuum and keep those filters clean. Wear a dust mask when working or finishing dried copper and bronze clays.

I highly discourage teachers from doing children’s classes using copper and bronze clays because of the health risks. The recommended exposure limits are set for adults and children are often more at risk than adults in these kinds of exposures. All of the exposure literature only considered adults. Stick to the much more biologically inert silver clays when working with kids.

Part 1 of the series on [Silver] Metal Clay Health and Safety
Part 2 of the series on [Copper I] Metal Clay Health and Safety


Lora Hart said...

Excellent advise Mary Ellin. I took a class with a well known expert in base clays a year or so ago. 12 people. Good sized room. Windows open for ventilation. The sanding dust was so thick (although not visibly) that I coughed for the next two days and one of the other students lost her voice for a week!

Sometimes in a classroom situation, strict safety measures may be a bit lax, but participants should ALWAYS wear a mask when sanding and finishing is going on!

Vickie Hallmark said...

Good topic for discussion, Mary Ellin! As someone with a history of asthma, I consider myself a bit of a canary for metal clay artists. Personally, I find myself to be sensitive to dust from bronze clay, whereas I've never had an issue with silver clay. I've realized that I need to wear a mask whenever I might generate bronze or copper dust.

Traditional metal workers and glass artists have previously learned the danger of ingesting metals. We'd do well to adapt their ventilation methods to our own studios.

Sarah Triton said...

Thank you for your hard work here, Mary Ellin.Based on this information, I've decided I don't want to teach with the base metals at all. I personally & professionally can't afford that liability, especially since I have no vent system (yet) in my studio.I will definitely change my own work habits !