Convergent Series

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

Archive for March, 2011

Other times, just waiting isn’t the answer.

Posted by C Scheftic on 2011/03/30

Here are a couple more of the pieces I tried, hugging silver metal clay around large copper sheet washers. I get the construction part of the process (where the silver is the potentially tricky part) but I’m clearly still trying to figure out the best finishing methods (with the copper).

The piece on the left was treated much like the one in my previous post. I did let it sit in the pickle a few hours longer as I worked on other pieces. There was still some firescale to grind off before I torched it to produce a range of heat-reaction colors. (It did take a bit less grinding than with the piece in my last post.)

The piece on the right is shown basically straight from the kiln. The red color, on the side that faced down on the kiln shelf, is closer to what I had been expecting for most of these pieces. I liked that red and didn’t want to do anything that might affect it.

This second photo shows the “backs” of both those pieces. The one that’s red on the front, with the semi-circle of silver, had been very black on the back (also, as expected). This shot shows what it’s like after I’ve ground almost all of that off. (I didn’t quite finish the job because I had to get them off to a friend who’s photographing them for another purpose … more on that in a later post.)

The piece to the left shows what can happen on the back of one with the torch-activated patina. It has a range of colors too, but they are darker, and with a rougher texture to them: a somewhat different look from what’s on the “front” but very interesting in its own way.

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Sometimes, you just have to wait a while.

Posted by C Scheftic on 2011/03/29

Here’s another “silver hugs copper” piece.

In this case, once again, I started with a washer-shaped stamping from copper sheet, and added a pair of simple silver metal loops around it. I pressed those together lightly at their ends, but did not press the silver down onto the copper. I pressed a “pilot hole” in the moist clay end; once it had dried I then drilled that to size. Then I fired it as usual for silver clay.

When that was done, once again, I quickly opened the kiln door, lifted the kiln shelf with tongs, and dumped the results into a bowl of room temperature water. That cooled it quickly to handling temperature. I repeated the attempt to reheat and requench (described in my last post) but that still yielded nothing that would “peel” off.

After several more tries I finally took the just-quenched piece, and dumped it into a bowl of bubbling-hot pickle (acid). I left it there for several hours while I worked on other things. Other than, perhaps, how long I had to let it sit (because I was using the weaker citric acid pickle, not the old sulphuric acid (aka battery acid) pickle), that’s my understanding of one of the traditional metalsmith’s ways of handling just-heated copper.

I could have left it to pickle for an even longer time. (I don’t have a photo of how this piece looked at that point….) The ugly black coating was somewhat thinner, but still evident.

So I took it over to my bench (in this case, a card table repurposed for use as a bench…) got out my Dremel tool, and started trying to “grind” off what remained. I got most of it off, except for a bit that was up right next to the silver bands. I didn’t have a good attachment for getting in really close without grinding off some of the silver. (I had one, but had recently chipped it doing something else silly, and have yet to replace that.) But, at last, I was seeing most of the copper.

What did I do at that point? I reheated it! Huh? Direct heating of “fresh” copper can do some nicely interesting things. So I got out my torch again, put a quench bowl right next to my firebrick, laid the piece on that, and fired away just until it started to glow. Keeping the heat on it as best I could–as with my earlier attempts at torching it, this takes a bit of simultaneous ambidexterity–with my other hand holding a pair of tough old pliers, I swept it off the brick into the bowl. This time, at least, it did what I was expecting: colors!

Although the exact results are always unpredictable. That is, I can’t guarantee, oh, “I want a bit of red here, green there, and blue over in that spot.” But you can say, oh, “I hope I get a nice assortment of colors,” and have a reasonable hope of getting that. They’ll be brighter on the side that felt the direct fire than they will be on the underside, but that’s just fine.

I liked how the colors of this piece turned out, at last, so I added a pair of bronze jump rings. The piece will eventually tell me what it wants to be hung from and with (probably while I’m working on something else with components that remind me of this one).

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While waiting for something to happen…

Posted by C Scheftic on 2011/03/28

Having finished, for the moment at least, my tales of my trials with Art Clay Copper, I figured I’d me mention something else I’ve been exploring at the same time.

One of the things about working with metal clay that really can suck you into it is this: There are a lot of times when you’re sitting there for a little while, waiting for something to happen (a component or a connection to dry out, some clay to rehydrate, some pieces to fire or tumble or react to a patina solution, whatever). It’s often not a really long time, but in some situations it is long enough that it’d be a shame to waste the time doing nothing. And, with all your metal clay and tools and everything sitting around, what better than to start work on a new piece?

So, while I was playing with copper clay, I was also playing with using copper sheet combined with silver clay. (I may eventually use both copper clay and silver clay to produce a single piece, but figured I’d reduce a few variables by first trying the regular sheet form of copper with silver clay.)

In the past, when I’ve mixed metal clay and copper sheet, I’ve combined them–after firing the clay to just metal–with any of a number of cold connection techniques. This time, however, I fired the silver clay right around the copper component. I started with some solid copper sheet that had been stamped out into a large “washer” size. I formed a bit of silver clay around it, and fired the two together. Now, the silver clay shrinks as it fires, which I think of as having the silver “hug” the copper.

This piece was fired at the optimum silver clay temperature of 1650. (Depending on the brand, copper clays may be fired somewhere between 1500 and 1800°F; the melting point of pure copper is 1984° F.) That 1650 temperature is, of course, well hot enough for various copper oxides to form on the copper.

As soon as this piece had fired, while it was still hot, I removed it quickly from the kiln (watching its red glow darken to black in the seconds it took me to move it) and quenched it in lukewarm water. A bit of firescale popped off from around the edge of the piece, but most of it remained on the two larger copper faces.

In one of her books, Hadar Jacobson mentioned that you could take a piece from the kiln, reheat it to a red glow, requench it, and the black should “peel of easily.” Now it wasn’t clear to me why I should have to reheat it if I’d done a quick-quench the first time, but I gave it a try. A little more black popped off from around the edge, but there was no peeling possible (let alone easily!) of the stuff on either face of this copper washer.

So I tried something else, suggested as one other alternative by Mary Hettsmansperger: brushing a just-cooled piece with a brass brush! That produces the interesting effect of turning the black coating to a sort of brassy-green color. It seems like that is stuck on: it still won’t come off at all easily. It does, however, tend to chip a bit at the edge, producing small brassy-black chips. I’ll have to wear it around a bit to test if that will eventually stop, or become more pronounced, or what. I’ll report my findings back here … eventually.

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Trying Art Clay Copper (Post #10 of … 10!)

Posted by C Scheftic on 2011/03/23

As I’ve said, I’m getting a bit tired of writing about this little group of pieces, and I expect you’re getting tired of reading about them. So this is the last post I intend to write about them (unless something really surprising should happen to turn up later on).

But I need to end the story somehow, so I will finish up with a couple of snapshots as I’ve gotten around to doing more finishing of them.

I finally broke out the radial bristle disks from 3M, put a small stack on a mandrel, and fired up the Dremel tool with that. It removed more of the black crud than had any other tool … though still not all of it from all the pieces. That’s really where I would have started with my clean-up attempts, except I don’t remember anything else I’ve read about using the Art Clay Copper having mentioned that, so I was just doing what others recommended…. Next time (which may be a long while for this product…), I’ll start with these and see how that turns out.

I started with the yellow (80 grit) and worked my way through 120 and 220, ending up at 400 on these pieces. Then I did some hand-polishing, with micron-graded polishing papers. (Not so much because I thought going to finer-grit disks couldn’t do it, but because I was still trying to get a “feel” for how these clays end up.) On the little fish, I finished up a silicone polishing wheel instead, which seemed to turn out just as well.

Finally, on a few of them I added a bit of patina, and polished up the high points. I’m not sure how long the color will hold, or darken further or wear off, or change and turn green (“verdigris”), but I’ll just have to wait and see. And then decide whether to apply patina to more of them.

For now, however, I’m moving on. More on several new projects in the next few days.

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Trying Art Clay Copper (Post #9 of ?)

Posted by C Scheftic on 2011/03/20

[All images in this post are composites that show both sides of the same pieces. One side of each set is to the left; the other, to the right. Clicking on any image should open a new window where you can see a larger version of it if you want.]

Four more hours in simmering pickle, and over an hour of concentrated dental-picking later, and they’re still not done!!! In addition to some remaining firescale, they still all need to be hand-polished and such. I will admit it: I am getting kinda tired of these 15 little copper pieces.

If one reason to use copper (aside from its lovely color, of course) is to help keep down the price of my work as silver prices soar, working with this copper this way isn’t looking promising. Yes, the raw material costs less, but the difference is eaten up by the hours (of my time) that will be required after firing. Yes, I can do other productive work while pieces just sit in the pickle. Yes, I’m still learning at this point, so I’ll likely find ways to speed up with trial and practice. But right now, what I have invested in these is far more than what I could ever sell them for had they been silver. And copper sells for less. I can picture getting the copper-work down to the same cost, to me, as it’d’ve been had I worked in silver. I’m having trouble picturing how to get the cost (materials + time) to come in at less. (And, yes, Art Clay Copper can also be fired in activated carbon, like the other copper clays, which should eliminate some of the firescale problems … but the point of trying it was to see if I could avoid the various other issues in using that technique.)

The two fish — the pieces that caused the whole episode of having to start a second packet of clay during the construction phase — have cleaned up nicely. The fan still needs some clean-up on the front, and the ginkgo needs a little on the back. But these four are in pretty good shape. The end of the work on them seems to be in sight.

The pair of matching wedding-love medallions don’t match. In my last post I noted the huge air-induced bubble on the one at the top. It’s a kind of nice effect; my only disappointment with it is that the other one didn’t react the same way! Both heart-sides cleaned up well, but dental picking was key there. (The top one was also polished with a Dremel tool. That didn’t help with the firescale, at least not via the attachments I tried, but it’s why that one looks a bit shinier than any of the others for now.) The bells still need a bit of work. Note that the bell that’s on the convex side of the bubble dome cleaned up a bit better than did the one that’s still flat. (Yet another reason I wish both had bubbled!)

The other pair of disks show something similar. They each have the same intricate texture on one side, and the one that’s on the convex side of the domed piece cleaned up well. The other one, on a flat piece, is going to require a good bit more cleaning: whether that means going back in the pickle or being attacked with more hand tools has not yet been decided!

Of the next five, the little leaf-shapes are in the best shape. The other three all still have a lot of firescale, on one side or the other. On the paisley shape, the most black is on the side that was facing up on the firing shelf, so that makes some sense to me. I’m sorry to see, however, that the patch I had made to the little ding the piece suffered while drying is one of the bits that popped off. (Please, can we just have the firescale pop off? What’s this with losing other bits as well!) On the butterfly, the most black remains on the side that was fired down, which is not how it’s supposed to work. Same thing on the long oblong shape: the blackest side was fired face-down. I can almost understand it for that piece: the face that was down was not really flat, so some oxygenated air could have slipped underneath. But it also disappoints because in the “popping off” action, a small area near the top (right edge, just under the smooth area at the top of the textured section) now has a small hole in it.

But the biggest disappointment is this last little pair. Even after almost seven hours in hot pickle, the black just will not come off them. And they totally defy the theory of less firescale on the face-down side, because the dense black — up in the indentations on the side that doesn’t have the little “snake” — is on the side that was facing the kiln shelf. I tried picking at them, just to see if it’d work, and it did not. These were meant to be used in an inexpensive little pair of earrings, and it is not worth my time to pick at them any more. They’re going to sit in the pickle until they clear themselves up, or they just disintegrate in the acid.

But I’m too tired to think about them any more right now. Polishing remans .. both to be done, and to be reported on.

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Trying Art Clay Copper (Post #8 of ?)

Posted by C Scheftic on 2011/03/18

A few posts back, I mentioned that I had my doubts about how well any of these pieces with components I’d squidged together would hold. Well, yes, there were some issues.

1. Edges that had looked perfectly smooth in the clay state now show gaps between two pieces that had been squidged together. While this can be an issue in any clay if you don’t properly finish the edges, with this product, even seams that had looked and felt well-groomed still reverted to showing their two-part construction.

To illustrate this point, here are four of the five pieces I made in Art Clay Copper using this technique, and three others that I made the same way with some form of silver clay (PMC+, PMC3 and Art Clay 650) that I just happened to have handy. (I don’t have any samples that used other brands of copper nearby to photograph.)

2. While the “snake” I formed to add to this piece seems to be holding well, it surprised me earlier by shifting a little bit as it dried. Originally, there’d been a big circle at the tip of this paisley shape. But, while drilling a hole in that from which I’d planned to hang the piece, I broke it off. Smoothing out the point, I decided to try this approach. I squidged the (still moist) snake into place, taking care to make sure it extended exactly over the pointed tip. When I came back the next day, after I’d left it to dry, apparently the shrinking clay had caused it to shift off that point a bit. (You can see how much it shifted by seeing how far off the point it is as the top of this photo. Had it been fully secured, there’s no way that could have happened. Other problems might have arisen instead, just not that…) By the time I saw this, it was too late to move it at all, but I wanted to make sure it was really secure. I re-moistened it, pressed it back down, and held it for far longer than I would normally do. At last, that did seem to hold. (This photo shows the piece fired, quenched, pickled, and dental-picked. Many of the little dots are still full of firescale…)

3. But my biggest surprise was the big expanded air bubble in this one. It clearly shows that some air had been trapped between the two layers, something I’ve never had happen when I used a similar technique on other clays. It is a somewhat interesting, if unintended effect. The only problem is, I’d made a “pair” of these, and only this one gained the bubble. The other one is shown, on edge, in the first photo above: both it and this show separation cracks around their edges.

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Trying Art Clay Copper (Post #7 of ?)

Posted by C Scheftic on 2011/03/17

I keep talking about the “stuff that popped off’ (or didn’t pop off as I’d been led to expect…) when I quenched my fired pieces of Art Clay Copper. It struck me that, if you haven’t seen this, you might not know quite what I mean.

The photo with this post shows what was left in my bucket once I poured off the water after firing my first two trays of this product. It doesn’t include what fell of either in the pickle pot or as I was cleaning up pieces that had been pickled, nor does it include what I managed to scrape off with a dental pick. Those actions, however, generated far less fall-out than did the initial quenching.

To give you a sense of scale: In all, I fired about 90 grams of clay. The copper oxides in that little plastic cup are somewhere between 2 and 3 tablespoons in volume. Admittedly, there’s a good bit of air in between all the little chunks but, still, it looks like a lot of “lost” copper to me…

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Trying Art Clay Copper (Post #6 of ?)

Posted by C Scheftic on 2011/03/16

OK, it’s time to return to my saga of trying the copper clay from Art Clay (Aida Chemical Industries).

While I was contemplating what to do with the six little pieces from my first firing, I put the second load into the pickle pot. And this is what they looked like after, oh, well more than one hour but a bit less than two.

I did fiddle with them a bit more before I thought to take this photo. I gave them a good rinse, of course. I then sat there for a long while, with a dental pick, chipping away at the remaining firescale. You can sort of tell where I had some success. The pickle-finish areas are pale, while the pick-cleared are a slightly darker, redder color.

The pick worked better along lines than it did in indentations that were more round. Thus, though I’ll still need to clean up those areas (with more pickling? or what else?), you may note the clearer areas (whether light or reddish) in the hearts (upper left), wedding bells (upper right) and the single flower (right side, second from the top). The little black dots in the wedding bells and both the paisley-shape (left side, third from the top) and the fish (bottom right) would not budge; neither would the random shapes in the deeply-patterned textures (left side, second from the top and center, second from the top),

I was too tired, by that point, to even contemplate dental-picking the butterfly at the bottom. But this part of the exercise did confirm for me that I didn’t make an error in career-choice. I would not have been happy, as a dental hygenist, doing this all day. I’ve always admired people who did choose that, and this little episode sure has confirmed that feeling!

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A small gap in the copper-saga.

Posted by C Scheftic on 2011/03/15

I haven’t finished posting my notes on working with copper, but I got sidetracked teaching half a dozen workshops and private lessons.

Those all used silver metal clay. (Ahh, the reliable stuff that I understand!) We made boxes (both lidded and sealed). We wove “flexible greenware” clay into interesting shapes. We made pieces that move via the use of “metal clay” rivets. Of course, I get so involved in the moment, that I don’t think to stop and take many photos. But here’s a small sampling, from three of my workshops this past week.

2/3 of the box-class at Zelda’s, packing up and looking very happy… The rest of the crew at Zelda’s, finished and happily exploring other potential projects
Michelle (who decided to increase the challenge in her own project) adding a hinge between two “woven” components. Sally, refining her little lidded box.

I love working with this stuff, but I also love helping others to create something with it that they can proudly wear–or give away–saying, “I made that myself!”

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Yes, it is a small world…

Posted by C Scheftic on 2011/03/13

When I teach metal clay classes, regardless of which clay we will be using, I always make a point of reviewing a brief history of metal clay: The products first released in the USA were from Mitsubishi Industries (PMC) and Aida Chemical Industries (Art Clay), both of which are based are in Japan. Those two are still the primary sources of silver and gold clays.

Some newer metal clays have been developed and released from other companies, in the USA (where I live) and elsewhere. But all metal clay artists should remember that our field has deep roots in Japan and, in particular, in that country’s scientific community.

After the earthquakes and tsunamis in Japan a few days ago, the latest word–at last–is that both metal clay teams (Aida and Mitsubishi) are safe, for the moment at least, as are their metal clay production facilities. This, of course, says nothing about their families, friends, and colleagues. Nor does it address the turmoil their country will undoubtedly face in trying to recover from recent events, both the original natural disaster, and the many man-made ones that are still unfolding upon that.

This post is just my small way of acknowledging their work, expressing my appreciation, and giving a small hint how much I want to wish them all well with what’s yet to come.

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Trying Art Clay Copper (Post #5 of ?)

Posted by C Scheftic on 2011/03/11

All my pieces have been fired and … sigh … it’s time to talk about firescale!

The first photo here shows the items in my second firing: taken from the kiln, quenched, removed from the quench bowl, and then knocked on the table a bit to see if any more firescale would fall off. Some did, but a lot remains. The darker-red colors in some of the pieces is what most of them looked like at that point. I tried using a steel brush on a few to see if it would remove any more firescale. Though that polished some of the darker red down to a lighter and slightly brighter copper color, it seemed to have no effect on the black bits. I was worried I might be burnishing them into the pieces, so I didn’t do much of that.

The six small pieces, from my first firing, were treated the same way, except I didn’t use the steel brush on them. Here, I did what was on the instructions, and moved them straight from the quench bowl into my pickle pot.

Now the instructions say they may need to be pickled for a few minutes. How many? Well, in part, that will depend on what sort of acid you use, and mine isn’t one of the strongest ones. I use, instead, one that’s based on citric acid: it’s still pretty harsh as far as acids go, but it doesn’t have as many nasty side-effects to people or the environment in general as some of the others. I know that, using it, I have to leave pieces in a bit longer than with, say, a sulphuric acid one. But, ummm, this is what the pieces looked like after two whole hours in the pickle, and then a good rinsing. You can see that some of the firescale is still flaking off, but there’s still plenty left…

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Trying Art Clay Copper (Post #4 of ?)

Posted by C Scheftic on 2011/03/10

In this post, I’ll say a bit about firing Art Clay Copper. It’s a different process than any of the other metal clays.

With silver clays, you arrange your pieces on a shelf and put that into the kiln. Then you turn the kiln on and, if it has a digital controller, you program that to reach a certain temperature and hold that for a specific length of time. When it’s done, you wait for things to cool down a bit (easier on the kiln itself, and safer for you as the operator), and then remove your pieces. Folks often just set their kilns to fire over night, figuring they can wake up to pieces that have been fired and cooled. If you want to take them out hot, however, you can either quench them in a bowl of room-temperature water or just let them air-cool on the shelf for a while before you touch them. (Other factors may be involved, such as whether they include glass or stones, but that’s the general process.)

With other copper-based clays, you fill a firing vessel with a layer of activated carbon, arrange your pieces on that, cover them with more carbon, and then (depending on which product you are using) may or may not put a lid on the vessel. Then you put that into a cold kiln, and proceed as with silver. For some such clays, a two-stage firing process is used; there are other variations involving whether you let them cool in the kiln or use a slotted tool to scoop them out of the hot carbon.

But the process for Art Clay Copper is different. Pieces made of this clay can be fired on an open shelf (just like silver and gold are). It is recommended that you put something on the shelf to help prevent the pieces from sticking to it: fiber paper or fiber blanket are two such possible aids to releasing the fired pieces. Once they’re all ready, you set them aside, and fire up the kiln. Your kiln should be empty, except for a few small posts that will, eventually, hold your shelf. You get it up to 1,778 degrees Fahrenheit first. Then you open the door (wearing appropriate safety gear), quickly insert the shelf with your pieces on it, and close the door again right away. You let it fire, like that, for 30 minutes.

This photo shows my kiln after two such firings. The yellowish discoloration along the top of the door is the result of previous firings. The dark brown streak up the left (hinged) side is new, from these copper firings!

And after firing, however, Art Clay Copper requires several additional steps. Before the firing time is up, you must prepare a bucket or large bowl of water and place it as close as you reasonably can to your kiln. Then, as soon as the firing is done and with the kiln still up at full temperature, you open the door, reach in with an appropriate tool (I used tongs) and grab the shelf. Moving as quickly as possible, you dump the pieces into the water to quench them. (Once again, dealing with pieces that have inclusions such as glass or stones complicates the matter more than I will address right now.)

Realize that, when you open the kiln door, the interior is all aglow. You can see the kiln elements and your pieces all bright from the heat. (You should, at this point, be wearing safely glasses with filters that will protect your eyes from the infrared glow, as well as gloves and clothing that will resist the heat!) But as soon as air from the room starts to rush into the kiln, the hot copper starts to form firescale oxides. It takes just a fraction of a second. So you have to act quickly, to minimize the amount of firescale that appears. And dumping the pieces into the quench bowl causes a lot of that black crud to just pop off into the water.

If it doesn’t all pop off, the instructions say that you can place the pieces in what is known as pickle, which is a metalsmith’s term for a hot acid bath. That should remove the rest. The word “should” in that sentence should give you a clue that there’s more to this story. That will appear in my next post.

For now, however, I’ll end with a shot of the two kiln shelves I used, showing what they looked like after being uses for this purpose.

On the one with the broken corner (it arrived broken, so that’s not a result of this process), you can see the residue from where the pieces did stick a bit, despite my having used some release paper. On both it and the other one (which I used for the first firing, with pieces aligned just along its left side as it’s placed here), you can see some remnants of that paper too. I’d not read nor heard any comments about that from others, so while I knew it was a possibility, it’s not really something I was expecting. I won’t be using these, or at least these sides, for subsequently firing silver pieces….

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Trying Art Clay Copper (Post #3 of ?)

Posted by C Scheftic on 2011/03/09

In my third installment of this tale of Art Clay Copper, I begin with a snapshot of the second tray of pieces almost ready to fire. (I’ll turn the fish so both are design-down, but I thought I’d show you the front of one for now.) As with the first shelf, it contains a mix of pieces I made over two days of working with the product. Before I talk about firing them both, I want to write a few notes about what this clay is like to work with.

In my first post from this series, I noted that my favorite for handling is Hadar’s Copper Clay (which comes in powder form). It has the most incredible silky-smooth texture when you work with it. The Art Clay Copper, straight from the pack, is a metal clay that feels much more like real clay (the kind potters use and gardeners hope to avoid). Once you’ve added lots of extra water to it (much more than with the silver clays), kneaded all that in, and let it rest a bit so the water can fully work its way into the binder, it gets to be much smoother. I never got either of the packs I tried to the super-soft feel that comes quickly with Hadar’s powder. (That’s just a comparison, not meant as criticism.)

But it was another of this clay’s handling characteristics that really surprised me. One of the techniques I use quite frequently with other metal clays (silver, bronze, and other brands of copper) involves making several components of a piece, letting them dry, then re-moistening the surface where they’ll connect to each other, waiting a bit for the water to soak in and, perhaps, adding more water if some areas dry out again faster than others, then putting the two pieces together with a motion that is often referred to as squidging.

Some people make attachments another way. They will thin down a bit of clay into a thick paste form, spread that all over one piece, then moisten the second one and push it into the paste. I’m not as crazy about that one, mostly because it leaves you with some paste oozing out around the joint that you then have to clean up. In most cases, the best way to do that is to let the paste dry and it will chip off more easily than will any parts of the original clay components. But it’s still messier, and the chipping is still riskier, than what you get through the squidge-process; and I’ve seen no prior evidence that the paste-seam is any stronger than one that has been squidged.

Though I’ve no clue why this is the case, I found Art Clay Copper very difficult to squidge! Most of the people I know (or know of) who’ve preceded me in trying this product are paste-users, not squidgers, and they have reported that it takes a lot of paste to attach pieces. (Like the comments about additional water needed while kneading the clay initially, however, further details were not readily available.) I guess that could have been a clue that squidging would be a challenge, but that hadn’t dawned on me until I tried it.

Squidging involves moving the two pieces you want to attach, gently and slightly but repeatedly, against each other. At first, they slip past each other very easily. You are creating a tiny bit of paste with the water and the motion; you don’t want to move the pieces very much, however, because you don’t want to alter the texture around the edges of either piece. After a few seconds, they stop slipping as readily. You feel them grab onto each other. At that point, you make sure they are aligned correctly, stop moving them, and apply a bit of gentle pressure for a few moments more. And they’re attached!

Well, that’s how it works with other clays. With the Art Clay Copper, I never got that moment of feeling them grab. I’d get the moment just before that one, as the slipping slowed, but not the definite grab. It took a good bit of pressure to get the pieces to feel like they were holding onto each other securely. I had the same reaction every time I tried this. (In the photo, above, that means with: the “matched pair” of big disks at the top, the ball on the piece at the upper right, and on the underside of the domed piece in the middle to the right. I also did that with the partial-layer on the two leaf-shapes, and the disk on the back of the ginkgo that are on yesterday’s photo.)

With other clays, all it takes is a bit of smoothing with a moist fingertip (or, in tighter spaces, with a moist rubber-tipped tool) to clean up the seam. With this product, it took a lot more effort at that point, and even required additional sanding (which I’ll do, when necessary, but really prefer to avoid as much as possible) to get a neat-looking seam. Even with all that, I set up both shelves ready to fire with only moderate confidence that everything will hold together well. Time will tell, I guess.

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Trying Art Clay Copper (Post #2 of ?)

Posted by C Scheftic on 2011/03/08

In my last post, I mentioned digging into a second packet of Art Clay copper. That was unplanned! What I’d expected was to come back the next day, do a bit of fine-finishing on the pieces that would now be fully dry, and try firing that first group of pieces.

What happened, instead, was that when I came back, I found that the bails on the back of the two fish had cracked and broken apart! I made the bail-pieces early the first day and set those aside to dry. Then I made the rest of the pieces, ending with the fish. I did it in that order because the fish were formed in a little push-mold, and I figured I’d just keep making other pieces until what I had left was around the right amount to use for those: it’s just easier to push the last bit of clay into a mold to finish it all off than it is to roll it out into some reasonable shape.

(This image is an excerpt from yesterday’s snapshot, showing how they looked shortly before I left the studio.) I’d never before used those fish molds for metal clay. They are bigger (both longer and deeper), and thus require more clay, than what I typically make with silver. I had used a few others around that size in other copper and bronze experiments, and they’d turned out fine. I often push a dried half-washer of clay (any variety) into moist clay for either decorative or practical (e.g., hanging) purposes, and it’s always been a simple yet effective technique.

I didn’t think to take a photo of these in their broken-apart state, but here’s my theory on what happened. I have pushed semi-rings into clay as deep (even deeper) than this before, or into a shallow spot with as much clay surrounding it on all sides, but never both at the same time. As all the surrounding clay dried and started shrinking, could the force of that have caused the semi-ring bands to crack? In fact, on one of them, it did more than just crack open. There was further shrinking after the crack that caused the two pieces to offset a bit and slip past each other. (Made me think of certain kinds of earthquake…)

Since I’d used up my entire first pack of Art Clay Copper in making these, I had none left for making any sort of repair! I had bought a second pack (the smallest size available is 50 grams!) thinking I’d learn from any problems in my first round and then have another go at it later on. Since I had to open that one just to repair the fish bails, however, I decided to keep going. I don’t yet know how long this stuff will keep once it’s been opened. I do know it’s definitely for far less a time than one can leave an opened pack of silver clay, because the copper starts to oxidize from exposure to the air. So I used up the majority of pack #2, but this time I did set aside a small ball just in case I later found I needed to make yet more repairs!

I ended up with a few more pieces than I could comfortably fit onto a kiln shelf and fire all at once. (I might have just fit them all, but this stuff requires handling while it’s all quite hot, which I’ll discuss in another post, and I wanted to be sure to leave enough room to get a good grip on the shelf with my tongs….) So I selected out a few small pieces to fire the first time around. I include a snapshot of those.

The little “fan” and “ginkgo” shapes are from the first day’s batch; they’re face down since that’s the recommended firing position for one-sided pieces. (The ginkgo is a shape I have used with those semi-ring bails pushed into the step. Since I was trying to end day #1 with nothing left over, however, and I’d only made one of these, I didn’t do that this time. In retrospect, I wish I had, to compare with the fish. Oh well, I can test that another time.)

The two “pairs” towards the right are reversible; they are set to fire with their “flatter” side down. The theory is that the bottom side, in contact with the shelf, will develop less firescale. While I think of the side you see on these pairs as more likely to be the front, the other side is also nicely textured, though flatter. I figured it would maintain better contact with the shelf, so it faces down. I’ll just have to see what happens. Stay tuned for that report…

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Trying Art Clay Copper (Post #1 of ?)

Posted by C Scheftic on 2011/03/07

Over the last year or so, I’ve tried several of the copper clays that have become available.

To date, Hadar’s Copper Clay has had my favorite handling characteristics. Most of the others come as a moist clay product, but Hadar’s is a powder that you mix with water to form the clay. It takes several minutes to mix up, but it’s easy to do. You mix just the amount you need and, once you get the knack of estimating quantities, you don’t have to worry about storing the remains of a partially-used package.

The thing I absolutely love about Hadar’s copper clay is how it handles: it has a wonderful, soft, smooth, silky feel. It’s easy to texture, roll, drape, fold, and otherwise manipulate. It works fine at a range of thicknesses.

I have had some problems with firing it, however, which is my main reason for exploring other possibilities. Like most copper-based clays, Hadar’s has to be fired in activated carbon (to produce an oxygen-reduced atmosphere that prevents the surface turning black from copper oxides known as firescale). While firing all metal clays involves a fine balancing act with time and temperature, so they sinter properly into “solid” metal without melting, it’s much trickier when (a) the stuff is buried in some sort of carbon and (b) the carbon needs to be contained in some sort of firing vessel. Why? Because both of those affect the temperature that reaches the pieces you are firing. And, to complicate things further, the various types of carbon and of firing vessel affect that in different ways.

This week, at last, I found some time to try the copper product from Art Clay (i.e., Aida Chemical Industries Co. Ltd.), so I’ll document my learning process here. I wish I’d posted more detailed notes on my earlier trials. This time, I plan to do a series of posts — I’m not sure how many it may take, thus the “?” in the title of this post — but I’ll just keep going until I’ve covered a range of items.

I’ll start with opening the package and preparing to work: I’d heard people comment that it took a lot of effort, kneading and rehydrating, to get this clay to a workable state. They were not kidding! I hadn’t understood why so many people had remarked that they’d had to add a lot more water than they expected. I’d thought, “Adding water to rehydrate clay is a common activity, what’s the big deal?” Well, let me tell you, it takes so much more, it’s easy to just lose track of how much you’ve added! I’m pretty sure that one package took a good six times more spritzes than I’d ever expect to add to other “fresh” clays. And another packet took more still; I think it was close to ten times as much, but that’s the one where I lost count.

But I’m getting ahead of myself by mentioning that second packet. Though I had several, my plan had been to just experiment with one; I’ll explain that later. I will say that, comparing the mixing of Hadar’s powder to the conditioning of this form, I don’t think I saved any time or effort there.

I did have a good laugh, trying to condition the clay. I thought of my friend, Barbara, who kept telling me I had to try this product because I was going to love it. Love, love, love it! And there I was, struggling to get it ready to work with, and it hit me: Barbara has worked for years with polymer clay. Of course she thinks nothing of all the effort it takes to condition this clay! I told her that, and she got a good laugh too!

For now, I’ll just include that snapshot of the pieces I made from my first pack of Art Clay copper, as they dry. The top three are fully reversible. The four smaller pieces, along the bottom, each do have a clear front and back.

I’ll try to post more of this tale each day or two until it’s done. I hope you’ll stay tuned!

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