Convergent Series

learning, using & teaching metal clay, and other aspects of life

Posts Tagged ‘Hadar’s Clay’

Pre-firing Hadar’s Clays

Posted by C Scheftic on 2013/04/14

A Bit of Background (skip to next section if you already know the science behind metal clay firing):

Stainless Steel Bowl with
base metal greenware
(yellow bronze and
burnished brilliant bronze).

The firing of fine silver metal clays is easy! Design, construction, and finishing are each more complex than the firing itself. Yes, firing does involve some details but, once you’ve sorted out placement, position, temperature, and time, you may just turn on the kiln and go do something else while the binder burns out, the metal particles sinter, and the load finishes.

Metal clay artists working with other metals, however, know that the firing process for those is much more complex. The difference is that precious metals don’t react with oxygen when they’re heated, but non-precious metals do react. This may cause undesirable color changes (such as firescale from the copper in sterling silver). Even worse, though, these reactions can change and damage the actual structure of the solid metal even if you’re working it at temperatures lower than where they’d melt. (This is not specific to metal clay: you can destroy other metal forms the same way.) Could you just restrict the amount of oxygen during the sintering process? Not exactly! Because the “clay” in metal clay involves binders, you first have to burn off all the binder before the metal particles can sinter. And, to burn off the binder, you need oxygen. In short: at first, you do need oxygen and then, later on, you don’t want to have it.

So each “base metal” clay product provides its own instructions for firing. These offer their approach for how to (a) allow enough oxygen to burn off the binder, while (b) still allowing the metal to sinter successfully. If you understand that as the goal, and like to play around, you can try various ways to make it happen regardless of what any particular manufacturer recommends.

(A couple of years ago I wrote a series of ten posts about my experiences firing Art Clay Copper according to their instructions. In the end, I decided that I was going to abandon Art Clay’s all-open-air approach, and stick to one of the strategies that restrict oxygen during sintering even for that product.)

Now, to the Point of this Post:

For many years, in the instruction manual provided on her blog, Hadar Jacobson recommended a two-phase firing schedule for her clays (which also required a cooling phase in between). It took a long time to complete a full firing cycle (basically an entire work day), but it worked. The length of the firing process did somewhat limit the number of production runs a metal clay artist could complete, depending on how many kilns you had available, but it was even more limiting in relation to most class and workshop settings.

At some point in the last year or so, Hadar started talking about a different approach. This one used something she called pre-firing (a relatively short (half-hour-ish) firing on top of carbon to burn off the binder) followed by one full-scale firing (where you then cover the pieces with carbon and fire for a couple hours to sinter the metal). Best of all, there was no need to wait between the two! Once pre-firing was done, you could proceed straight to the final firing. That pretty much cuts in half the time required to fire a complete load.

Hadar offered two suggestions for doing this pre-firing. In each, you place the pieces on top of a layer of carbon inside an appropriate firing vessel. Then you burn off their binder either:

  • on the top of a gas stove burner, or
  • inside a kiln.
No Flake Foil Box with
six pieces of
base metal greenware &
one repair to re-fire.

Regardless of which device you chose to use, you would then cover the pieces with carbon and follow up with a firing that was pretty much the same as her old phase-2 process.

I tried it both ways and, suddenly, I began having all sorts of problems. Yes, they were ones I had seen before, but then only rarely, and they had provided enough clues for me to quickly diagnose any problems and fix them. Now, however, I was not finding ways to fix things. And, hey, the old method might have been long, but it worked for me. So I kept on using it.

But with the latest version of her Instruction Manual, Hadar has stopped even mentioning the old way. And pretty much everyone in the group of teachers going for accreditation in her program seemed to have shifted over. So, sigh, I’ve spent the last few weeks simply trying to figure out open-air pre-firing for myself.

I have not yet mastered the in-kiln method, but it seems I’m not the only one having some trouble with that one. The problem there is that, sometimes, part of the binder on the “down” side of pieces does not burn out, so the metal then cannot sinter. This may stem from the fact that, with no heat coming up from the bottom, the carbon is insulating that area too well. Heat will reach that side of each piece, eventually, once the carbon itself gets hot enough, but that may risk leaving top-sides exposed to oxygen for too long. Another approach, trying to solve that by turning the pieces over during the pre-firing, means handling very hot pieces in their most fragile state, de-bindered but un-sintered. No, thank you! Some people seem satisfied to solve this dilemma by simply firing their pieces twice, once with each side up; but if it takes that much to get them to sinter I figure I might as well just stick with the older method.

Stainless Steel Bowl with
de-bindered base metals.
(Re-fired piece is the one not black.)

But I think I am finally getting the hang of the stove-top method!!! The problems I’d been having were that my pieces were curling and/or cracking, which I knew meant they were getting too hot too fast. Hadar kept talking about turning the heat down if you saw the pieces on fire, but I never saw any flames. She talked about turning the heat down once you saw binder-smoke starting to appear, and I was taking a lot of care to do that immediately. She and the other instructors talked about how long their pre-firings took, and mine were well within those limits. After multiple attempts, I finally figured out that I really did have to heat the pieces on a very, very low flame. Maybe it’s just my stove, but I’m down to a mere fraction of the flame I’d use simply to boil water. Curiously, doing it this way does not seem to take much longer over-all than what I’d been doing before: it takes a bit longer before I see any binder burning off, but the pieces blacken completely rather quickly.

Another problem I’d had was that sometimes one or even a few pieces would not seem to burn off their binder. But I’m getting better at moving the container around over the flame, when that does happens, which seems to solve that.

I am still having the occasional failure (i.e., a bit more often than the old way), but I’m clearly making progress here. All seven butterflies in my last mid-fire load, for example, turned out fine.

Seven Butterflies
with two polished
to confirm sintering.

But, there’s something else to consider. In addition to the time that is “lost” to the occasional failure, one also has to actively watch the entire pre-firing process. You can’t do anything else useful. Well, maybe you can; but I sure can’t. It happens too quickly to catch a brief nap (yeah, I’ve been known on occasion to sleep through an entire silver-load); and it takes too much attention to spend time doing fine-finishing on pieces from the last load (which is what I usually try to do during firings). With silver pieces, I never really counted any “firing” time into their cost because I could accomplish other things while that was happening; with these pieces, however, now I do have to factor that into the price I charge for them. (I’d have that same dilemma with the in-kiln pre-fire method.) So I’m still trying to figure out how I feel about all this, but at least I have that feeling of accomplishment over approaching mastery of what currently seems to be the most popular method for pre-firing Hadar’s clays.

Seven Butterflies with
preliminary polishing complete.

By the way, even though I really am kind of swamped with to-dos, I finally figured out a way to add captions to photos that would work with this blog! It was easy, once I spent a bit of time on the task. I mention it, however, because there are some other metal clay hints buried in those notes; I’m really hoping to find time to write more about other aspects of firing in the coming weeks….

Oh, and all the pollinator-pieces used as illustrations here will be available at the Western PA Garden Marketplace on April 20. It’s not an art-event: the emphasis is on gardens and landscaping. My being there is just a little “bonus” treat, on top of all the plants and garden supplies. But if you’re reading this from the western PA area, it’d be great if you were to stop by and say “Hello!” on Saturday.

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Posted in General Techniques, Learning Metal Clay, Technical Details | Tagged: , , , , , , | 6 Comments »

Accreditation Program for Hadar’s Clay™ Teachers

Posted by C Scheftic on 2013/03/08

Well, I still don’t seem to have my head above water, schedule-wise, but there is a bit of news I’ve been sitting on for over a week now, and I just have to say something about that!

I have mentioned Hadar Jacobson in this blog before. I’ve found myself inspired by much of her metal clay art. I really enjoyed participating in a workshop she taught here just about two years ago (which I reported about in a series of six posts that started here). I find her clays to be delightful to work with. And I’ve been honored to have three of the pieces I’ve made using those clays selected as illustrations in two of her books.

And the latest news items, both Hadar-related, are these:


  1. She is starting an Accreditation Program for Hadar’s Clay™ Teachers … and … [drum roll …] …
  2. She has invited me to be in the “charter group” of teachers to participate in this!

(If it weren’t for the jaw-pain that, at the moment, I know would result from jumping up and down (even just once, let alone for days on end now), I’d show a video of that here. Instead, I’ll just include a photo of of one of my pieces from her book, Patterns of Color in Metal Clay.)

Now, we are just at the beginning of a year-long process. On the one hand, I am thrilled that there will be a cadre of us (all around the world!) spending pretty much a whole year working on a series of common projects, talking about the results, comparing notes, seeing what is and is not reproducible and what really does vary by individual, how to handle all this in various situations both in-class and on-line, and more, all culminating in a series of get-together workshops next year. On the other hand, I am also a bit intimidated to think that this will take a whole year of regular tasks and assignments just to get through the process, so I’m betting that some folks will drop out along the way. At the moment, I am simply hoping that I can hold on (although, of course, another part of me really does want to make it through “with flying colors”…).

But one of the things that really helps to maintain my fascination with the whole metal clay / powder metallurgy process is how intrigued I am by the continual learning that I am privileged to gain with it, and the opportunities I then have to share all that with others through classes, workshops, demonstrations, publications, and more. So that is the spirit in which I accepted the invitation. We’ll just have to see how it goes!

Posted in Learning Metal Clay, Teaching Metal Clay | Tagged: , , , , | 1 Comment »

Translation, please…

Posted by C Scheftic on 2013/02/28

Here’s something else I make at times, something that ties in with the theme of my last post about using bits & pieces of clay that may be left at the end of a session. (Well, sometimes I deliberately save little bits of clay during a workshop, so I’ll have some left in case a student has a question that’s best answered with a quick demo. That’s actually how I ended up with so many of the oak leaf bits shown here….)

Can you help: I’m trying to figure out what to call the resulting pieces!

My inspiration for little pieces like these are “chopstick rests.” In transliterated Japanese, I am familiar with the term hashi oki for that use. According to Wikipedia, the transliterated Chinese term is kuaizi zuo. Shown are examples of such little items that I sometimes make with the remaining bits of clay at the end of a session. All of these are bronze. If the kiln happens to produce lovely colors, I leave them as-is; otherwise, I polish them up well; I tend to combine them in non-matching mixes. (Having three such pairs itself is unusual! And, yes, the photo deliberately shows an odd number of them!)

Sometimes I make slightly larger, more complex ones too, and do that more-deliberately (that is, not just with leftover bits of clay!). I’m completely sold out of those right now, however, and don’t seem to have any good photos of ones that have moved on to new homes. But in his excellent book, Metal Clay Fusion, Hawaii-based artist Gordon Uyehara includes a sample project for making several different styles of seashore-themed hashi oki, so metal clay artists may want to check that out.

The thing is, now that I’m located in Southwestern PA, I don’t come across many chopstick-users. When I host a dinner where I set the table with those, I often have to teach diners how to use them! Even when people are already comfortable with them, often they are still not familiar with the use of little stands to keep the chopsticks both in place and off the table / tablecloth itself.

I do, however, know lots of artists and craftspeople who use specific hand tools that might benefit from a creative little resting-place. Shown farther down this post are two of the tools I often use, a colour shaper and a ball burnisher resting on another such piece on my own worktable.

What should I call these items when used that way? Now, I do believe that oki is fine to use for the “stand” or “rest” part of the name. But hashi for “chopstick” is not. What is?

I asked the person who teaches Aikido Kokikai down the hall from my studio (and has spent time studying that in Japan). She was, of course, a bit concerned by my “westernization” of this “traditional” idea: why not just call it a tool rest? When I explained how much I valued the “art” aspect of hashi oki, rather than the strict utilitarianism of a “tool rest,” she was a bit more willing to consider this. Not a native speaker of Japanese, however, she said that the best phrase she could come up with was dohgu oki. Except, she said, dohgu expresses the idea of equipment, more than a simple hand tool, but she could not think of a Japanese word or phrase for the generic idea of a small hand tool like this.

If you can help me out with this, please leave a comment on this post. (Make sure to leave your email address–this is something I can see but it is not automatically posted in public with your comment.) If I end up using your suggestion for this, I’ll be happy to send you a little set of these pieces if you’d like. (If several people suggest the same name, and I pick that, then I’ll draw one at random.) The offer remains open until I pick one and post my choice in the comments.

Please help, if you can! Thanks….

Posted in Misc. Musings | Tagged: , , , | 3 Comments »

Bits & Pieces

Posted by C Scheftic on 2013/02/23

I’ve been meaning to write for a while about several questions that often come up in workshops, especially with beginners when each person is allocated a package of clay and then finds they don’t use all of it: why did you give me more than I need and how do I save it for later use?

I see the answers to these questions as being connected, but let’s start with the first one: for many “projects” it is just worth having a bit extra as you roll it out, so you’re sure to get a big enough area to cut out the shape you want. While this remains true no matter how experienced you become, it is especially important for beginners who are just learning the various ways to manipulate clay.

The answer to the second question is a bit more complicated. Silver clays come in a well-sealed package, and can remain in great condition for a rather long time inside that. The trick is that, once the package has been opened, all sorts of things can happen. At a minimum, the clay dries out. If that happens, it can be rehydrated: ways to add water to get it back to working consistency is something I’ll try to remember to write about at some point in the future (even though it’s not something I encounter myself on a regular basis any more…). If you’re going to use the remaining clay again fairly soon, you can just try to keep it moist. There are all sorts of products you can buy, or build yourself, to create a little humidified storage environment. The problem with doing that for any length of time (and something that the product vendors rarely address) is that your clay can easily become contaminated with mold. Now, you can add something to the environment (not to the clay itself, but simply inside your storage box) that can help retard mold growth. White vinegar or lavender oil are examples of some mold retardants. And, even if your clay does acquire a bit of visible mold, it’s not a crisis. At that point, your options are to scrape off the mold or to just work with it. (You do have to take care with the latter because the extra “space” taken up by the growing mold may create spaces in your fired piece that may influence its look and/or interfere with its strength.) But, in my experience, there’s a much better solution: don’t even try to store it!

That is, my general answer to both of the original questions is this: why not see if you can just use up any remaining clay in some creative and productive way?! Add to your current piece, or make something else.

One of the earliest “lentil” shape beads I ever made is shown in an old photo here, to the left, strung with some Russian jasper and green glass beads. (It’s also one of the pieces that led me down the path of making reversible pendants!) Its other / first side had a more elaborate design; what at the time I thought of as the “back” had the simple, low-relief, fleur-de-lis pattern shown here. After decorating the first side, I had a bit of clay left. I rolled it all out, just two cards thick, which got it big enough that I could cut out a small square. I put that on the same drying form I’d used for the lentil (so it would have the same curvature) and cut a circle out of the center of that. With the clay left over from trimming the square and cutting the circle, I made a number of little balls and let those dry too. Then, I moistened the center of the fleur-de-lis side and the underside of the open square, and stuck those two pieces together. Once those seemed secure, I added more water inside the open circle, and pressed the little balls into place. Having the circle around the outside of the balls gave me a way to make sure I could attach all of them securely, to that ring and to each other, rather than trying to count on a small point of connection on the bottom of each ball. And, suddenly, after investing only a few more minutes and a tiny bit of “left-over” clay, the piece became reversible, which sure seems like a good deal to me!

Of course, if you have more clay left over, you can always make something else with it. All of the elements in the silver and bronze earrings shown in the smaller image to the right were made when I had some larger leftover bits. After completing other pieces I’ve often used any remaining clay to make little patterned disks, or cut out little textured designs, and just set them aside to dry. When I’m firing up a load in my kiln, if I have a bit of extra room, I pop them in. When I have a few spare minutes–with metal clay, one always seems to have moments of waiting for something else to happen … to dry, to rehydrate, to finish firing or cool off, for example–I will go through these bits and pieces, and assemble them into something interesting. Their small size, of course, means they often (but not always) become elements in earrings.

Sometimes I’ll add other elements to such “bits and pieces” too. The orange-and-silver earrings shown at the very top of this post were done that way. When I fell in love with the little colored lucite flowers, I bought a small collection of them to use both for my own creations and during workshops. For several months, whenever I’d have a little bit of clay left over, I’d make a little flower disk or leaf of some sort. I kept track, so that I’d end up with matching pairs, but I didn’t worry about completing any particular number at once. I just used up what I could for some larger shapes, made smaller ones when I had less clay left, and made other small elements or even just tiny balls with the very end of the clay I had on hand.

In fact, for silver pieces that I intend to fire first and figure out how to use later, those I make flat. Then, when I do decide where I want to use them, if they need some shaping for that particular purpose, I can use the “traditional metalsmithing” technique of dapping the fired pieces to shape them as needed. That’s what happened to the little flowers I set on top of the blue-and-white glass beads shown with the earrings in the final photo here. In fact, though I made those flowers specifically to use with these beads, I could not have domed them to match their shape in the “dry” state because I punched them out of a little bit of extra / scrap clay that I had mixed up so it would remain flexible as greenware. I had finished the project I wanted to make with that clay and had some left then too. Since I knew that “flex greenware” clay that has been rolled out is great for using with paper punches, I used some of my leftover clay to make a small sheet for punching. I then made these flowers but they had to be fired flat … since they were too flexible to hold any other shape. (I also rolled the final bits of that flex-clay into long “snake” shapes that would remain flexible and could be used to embellish other pieces later on.)

I will note that, while fired silver and copper clays can be dapped after they’ve been fired to metal itself, the various bronze clays that I enjoy working with cannot be formed much (if at all) after firing. That’s just the nature of bronze, not simply the fact that it came from metal clay.

I do sometimes wonder how much this is something I do, myself, verus what other metal clay artists do with their leftover bits of clay. I know that a number of you do read this blog (without commenting) but I sure hope you will speak up now: Do you do this too? Or what?? And, why?

Posted in General Techniques, Teaching Metal Clay | Tagged: , , , , , , , , , , , , , | Leave a Comment »

2012 Art Buzz Tour — This Weekend

Posted by C Scheftic on 2012/12/03

Have you heard the buzz? It’s even louder this year! Over forty artists! Seven sites! All in the Pittsburgh area’s “East End” this weekend. And my studio is one of the locations on it again this year.

At WSCC (where I’ll be), the Holiday Gift Shop will still be running downstairs, and I am pretty sure that Daviea Davis will have her glass mosaic studio open too, upstairs across the hall from mine.

2012 Art Buzz Map

If you’re in the area, I sure hope you can stop by. To say, “Hello” and “Happy Holidays” at least. If, for some reason, you can’t get yourself there in person, how about leaving a holiday greeting as a “comment” on this blog post. Even having you say just “Hello” or “Happy Holidays” would be much appreciated!

I look forward to seeing / hearing from you, dear readers, so I can extend my best wishes for this holiday season to you too, in return, in a more personal way.

Posted in Events, Studio | Tagged: , , , , , , , , , , , , , , , , , , , , , , , , , , , | Leave a Comment »

Art Buzz Tour — This Weekend!

Posted by C Scheftic on 2011/12/09

Have you heard the buzz? Eighteen artists! Seven sites! All in the Pittsburgh area’s “East End” this weekend. And my studio is one of the new locations added this year….

Map of 2011 Art Buzz tour

If you’re in the area, I sure hope you can stop by. To say, “Hello” and “Happy Holidays” at least. If, for some reason, you can’t get yourself there in person, how about saying “Hello” or “Happy Holidays” or something else even more interesting as a “comment” on this blog post.

I look forward to seeing / hearing from you, dear readers, so I can extend my best wishes for this holiday season to you too, in return, in a more personal way.

Posted in Events, Studio | Tagged: , , , , , , , , , , , , , | 3 Comments »

 
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