Science Project: Fine Silver Metal Clays

(Ongoing discussion of the day to day work on this project can be found on current and archived Web Journal entries on my web site, www.katemckinnon.com.)

This work is in progress!

Updates coming soon from my July 25 visit with the Uinversity of Arizona's GC-MS (gas chromatograph / mass spectrometer) machine, to see what the heck is in PMC and ACS binders, other than fine silver and industrial cellulose. It was fun, informative, and we'll be doing step 2 of the tests soon.

Next steps: Second GC-MS visit, letters to the authors and instructors teaching the use of Styrofoam, Styrene, Polystyrene, or floral foam burnout cores.

The page and the discussion are evolving, and I do welcome your comment or contribution. So far this work represents only my current research, and my opinions, with the intention of organizing my thoughts in preparation for further work and debate. I welcome discussions of these issues in any public forum, and would like the opportunity to participate. Forward me links to any discussions you think are material. Reach me at:

This page is presented as an overview of my ongoing research into the current practices in the field, and the relative safety and effectiveness of various working and firing techniques. If you want to refer to this discussion in forums, it would be best to just give a link back here, which would be http://www.katemckinnon.com/metalclay1.html, and let me speak for myself. I'd appreciate you letting me know of any serious discussions of this topic, because I don't follow the forums and I'd like a chance to contribute. And I thank everyone who is sticking with me on this. If you'd like to be on my list of people willing to sign onto my letter, email me at the above address and let me know. The more signatures, the better. Please let me know, when you email, what your experience level with metal clay is, and whether you have taken or taught classes in the field.

All work (even the contribution of the Mass Spec lab at the University of Arizona) is being donated, and we are doing it solely out of concern for the hundreds of thousands of people using these products. Our only goals are improved awareness and safety practices, and no liability to any person, firm, or studio is implied by my preliminary work. You will just have to review the facts for yourself, read the MSDS sheets, read up on the chemicals, and draw your own conclusions about what is and isn't advisable. I'll be publishing my part of it in my book, Structural Metal Clay, so if you'd like to support my end of the work, the best way is to just buy a copy of what will be a delightful book in any case.

My thoughts at this time are simple- I believe that the kilns should be fired either in fully ventilated spaces, or out of range of living beings, and that no one should ever fire plastics or foams as burnout cores for hollow beads. I want our teachers to be fully educated not only on safety, but also on the amazing potential of the metal clays, and why it's best to fully fire them. I'd like everyone who teaches metal clay to fully comprehend annealing, fusing, sintering, and work hardening. Metal clay is a product that can be used very safely to produce wonderful works in metal, and it discourages me that there is so much incorrect, incomplete, and in some cases dangerous information out there.

My goals are even simpler:

1. No more kilns in classrooms unless the show, studio or bead shop has industrial-grade ventilation. Even the burning binder is not fit to breathe- it contains industrial-grade cellulose, which is not rated for human consumption. Breathing is a more direct method of consumption than eating, and as a matter of courtesy and caution, the fumes of any type of combustion should not be vented into enclosed classrooms. We have no way of knowing which of our students are pregnant or otherwise sensitive to the materials being combusted.

2. An acknowledgement from Rio Grande, and their senior instructors, that it is inadvisable to fire polystyrene, styrene, or styrofoam without industrial-grade ventilation, and that the risks for pregnant women and their fetuses when exposed to those fumes is unacceptable. There is no situation in which this is necessary, and I know Rio to be a company that would not knowingly promote dangerous practices in its official classes. I realize that ceramicists and casters do it all of the time, and I point out that neither profession is known for its health benefits. Yes, chemical companies pollute the rivers and yes, our Great Lakes are toxic, and sure, we are surrounded by poisons every day. This is no reason for you to poison yourselves, your students, or their unborn children further with burning plastics. There are at least five best-selling PMC videos or books that need to be taken off the shelves or re-edited to un-recommend this practice.

3. Better education on the dangers of torch and gas stovetop firing, and an understanding that the process produces binder smoke directly in the user's headspace, and an inferior final product.

4. An improvement in the general education of our teachers regarding the full potential and metalsmithing applications of the products.

Just a little disclaimer, for anyone who thinks I'm coming at this from some sort of Ivory Tower Of Perfect Safeness. I'm concerned only in matters of professional responsibility here. Sure, I keep a clean bench, and I'm careful with metals, but I'm any manner of fool in other areas. I'm as naughty as can be. I sleep on memory foam, which is chemically ghastly (but so soft), I eat things I shouldn't. I've entered strange woods with hand-lettered "Keep Out" signs, I've gone down the rabbithole and I peek off of the edges of tall buildings and cliffs. I'm only addressing our accepted professional and teaching practices.

I think that the key issue to focus on in these discussions of safety is the concept of early pregnancy. No one would claim that we should be cavalier about that, and since females themselves have a difficult time knowing that they are expecting in early weeks, we ought to conduct our classes in a manner that sets a standard that results in air safe enough for a pregnant woman to breathe. We could argue until the cows came home about what was safe for a grown adult, so I'd like to sidestep that discussion entirely and focus only on what is obviously and provably true.

Kate's Table of What People Do revised July 24, 2007

Is it...

Potentially Deadly? Dangerous? Inadvisable?

Firing Styrofoam, Polystyrene, Styrene, or other plastics in a room with poor ventilation. Read their MSDS sheets, and read carefully. The scariest thing about them is how safe they make the products sound. In truth, styrofoam emits hydrogen chloride and hydrogen fluoride in a thick black smoke when burned. Polystyrene, which sounds safe as toast at first read, emits benzene and Styrene. Styrene may be the worst, as it is a known embryotoxin, and easily crosses the placenta. Think on that.

How much poison you ingest depends on how much you are burning, what your ventilation is like, and how big you are. Very small amounts of styrene might just give you a headache, but can harm a fetus. When you see the words "human mutagen" or "human embryotoxin," you can be sure that these chemicals and compounds are dangerous.

As the majority of our students are females, and at least half of childbearing age, these concerns are very serious ones for our field. Also, many women in very early pregnancy (when the fetus is at highest risk to mutagens) do not realize that they are pregnant. In this case, safest behaviors are called for in every class.

Unfortunately, and mysteriously, I do not yet have the agreement of the senior PMC instructors on the dangers of burning plastics. In fact, here is a link to a published tutorial from the PMC Guild, which features a project firing Styrofaom, and a project firing floral foam. Instructions just say "fire as usual," with no health warnings or mentions of how dangerous the firing is.

Remember that toxic exposures can be cumulative.

 

Fuming, soldering, or otherwise vaporizing metals without ventilation. Solder and flux give off a rainbow of toxic fumes and gases, including those listed above. Fumes from vaporized gold can include cyanide and arsenic vapor.

(Hot sulphiric, nitric or hydrochloric acid isn't so wonderful either, and one or more of these can be found steaming up from most metalsmithing pickle pots. If you use fine silver instead of sterling, no flux or solder are needed to join, and no pickle is needed to clean the metal.)

Firing Styrofoam or plastics in a kiln, or soldering or fuming, without an industrial fume hood or really good ventilation. If you can smell it, you're breathing it, and that means that it's going directly into your bloodstream and interacting with your central nervous system. (This is bad for anyone, but see the previous column for notes on early pregnancy.)

 

Firing kilns of any sort in enclosed classrooms with poor ventilation and little or no knowledge of the sensitivity of students, or of your legal liability if something unthinkable happens. Run your own business? Do you know what your liability coverage is?

 

Breathing the products of combustion of unknown materials. Be wary of cork clay and other fillers- industrial-quality ventilation is required if you don't know what's in it, or where it's made. Torch-firing metal clays generally involves the artisan standing over the piece that is firing. Do this only with real ventilation- your kitchen hood isn't good enough. (And know that those pieces will never be as sturdy as those fired fully in a kiln.)

 

Breathing metal dust. Like asbestos, crystalline or spiky particles tend to stay in the soft lung tissue and accumulate. Metal that is inhaled tends to stay in the lungs for life, and can complicate conditions such as asthma or emphyzema. Excessive exposure to inhaled metal can cause metal poisoning. Grayish skin and mucous membranes are often the first sign of toxic exposure. There are many ways to keep the dust down. The best is not to excessively file or sand the dry clay. If you need to file or sand, do it outdoors if possible. Consider wearing a fine particle respirator if you file or sand.

 

Believing automatically what manufacturers (or individuals) tell you when they are making a profit from your consumption of a product. Unfortunately, we have plenty of references on that one. PMC and Art Clay Silver have every reason to encourage people to torch fire and to underfire, but they should at a minimum recommend ventilation for firing.

Breathing the products of any combustion without ventilation. This is just common sense. If possible, avoid breathing smoke and dust with unknown ingredients. If you can't eat it, you definitely shouldn't smoke it, as inhaled toxins go directly to the bloodstream and the central nervous system.

Remember, not even our senior instructors and distributors really know what the secret ingredients in the metal clay binders are.

 

Filing or sanding all metal clay as a matter of policy. Why make unnecesary metal dust? We've got to do it once in a while, but in general try just gently stroking a cut edge when it's freshly cut and save sanding for designs that require it. (Try it! It's easy. You don't need to use any water, just gently stroke or pat a fresh cut, immediately upon cutting, and see how lovely your edge is.) Please don't teach the "cut it sloppy, sand it dry" method of working.

 

Getting covered in metal clay slip or dust while working. Again, this is just common sense. No need to be a clean freak, but remember that your skin is your largest organ, and is highly absorptive. In general one should eat, breathe, and rub into the skin as little metal as possible.

 

Teaching metal clay classes with only a basic certification class under your belt, or relying exclusively on information gleaned from such a person. Certification classes are designed as an introduction to product, and an invitation to participate in a discount program. The courses are not comprehensive, and do not present enough information about safety, and the potential of the product, to prepare you to teach others.

 

Underfiring or short firing metal clay, when you have the opportunity to fully fire it. 1650F, for two hours, is ideal for all fine silver metal clays. Work down from there as necessary, or re-design pieces for better firing. Pieces fired for shorter amounts of time or at lower temperatures will never be as sturdy as pieces that have been fully fired. The fusing temperature, or the temperature that fine silver completely softens and melts together, is 1761F. Our goal is to come as close to that as possible, without losing any surface detail. 1650F is ideal for this purpose and will give you the best finished metal.