Friday, January 30, 2009

Choppin' up some ponies

I wanted to pull something Sarah said from the comments section, since it is something that I'm mulling over right now.

(1) Could casting these small pieces "on the half-shell" (split up the median) then assembling them in greenware be doable/useful?

(2) Perhaps cutting problematic legs off, probably in the triceps area and biceps area (so they "lock" better) and casting as separate pieces might be the only way around it?
As many ceramic collectors already know, earthenware horses have historically been cast whole. This is how Hagen-Renaker made their horses, and then later how Joan did most of the production horses at Pour Horse.

But European bone china and porcelain have a different tradition, one where the horses are cast in pieces and reassembled. After Joan formed Marcherware with Mark Farmer of Alchemy, she began experimenting with assembled pieces. The process makes it possible to cast more complicated horses. Horses with twisty bodies and swirly hair bits - Sarah's specialties! It also makes it possible to cast much larger horses than we've done before, because the individual molds are more managable. (A whole-body mold of a traditional-scale horse, when wet, is too heavy for most of us to lift.)

But this is all a rather new direction, and we're still learning what might and might not work. Doing it on a small-scale horse like Vixen or Taboo is something that hasn't been tried. We don't know quite what to expect, or which approaches might work best.

So back to Sarah's comments. These are the things that I have been pondering lately while making (properly soaped) production molds for Imp. Having clayed Vixen up (four times), it's really clear to me that her extreme head turn is going to make whole-casting problematic. Her body just occupies so many different planes. I don't think she will work without cutting her up somehow.

And I had thought about Sarah's first suggestion, which is cutting her in half down the dorsal line. This is how the horses used by military figurines are made, though of course those are typically made from injection molded plastic. And I would need to exclude her neck and head, since it would be really hard to work in that area (to fuse the two halves) without damaging her face. I'm also not sure that it will help with her because bends so much.

What I think will work with her is removing her forehand. Or rather, removing her head, neck and left leg and shoulder. That way my fuse line falls predominantly to the chest and underside of the horse (where any shadows created by the fuse line might be less visible). And I can pour the piece through the big opening of the body.

Of course, I could get lucky a second time. Maybe she will work with just an inset piece over her turned head. I'm going to pour a number of rubber copies, because I think it's going to take some experimenting to find what will work. But she looks like the kind of piece that might push the envelope a little, and that's always good.

Tuesday, January 27, 2009

A day in which I play Junior Scientist

Shortly after I met my husband, we both were given one of those Myers-Briggs personality tests. My test came back saying that I preferred "feeling" to "thinking". In fact, I topped out the score in that particular category. It is no surprise, then, that I was never particularly attracted to engineering.

So it must amuse my husband that I now routinely come to him (a definite "thinker") with engineering-type questions. I certainly have come to appreciate good problem-solving skills.

And that is what I needed for the problem with my inner pieces. I needed a way to seal the surface, and only the surface. I had already wondered if it might be better to spray some kind of sealant on them - something that dried almost immediately upon contact. My husband's suggestion was that I find something with a wax base, since that not only would sit on the surface but could probably be removed with rubbing alcohol. He thought perhaps furniture wax might do the trick.

I decided to set up a test to see what might waterproof my plaster without soaking it through.

I didn't want to wait for plaster to dry, so I used the backing off one of the bad Vixen rubbers. (I should note that here is where I made my first miscalculation. Well, make that plural. Did I mention that this post could also be entitled "How Lesli wasted a perfectly good day in the studio"? Anyway, the plaster should have been damp, not dry, because that's how the plaster is when the mold is being made.)

All I had to do was sand off the keys and make it 1/4" thick. As this picture shows, I made a rather big mess. But I got my thin slab of plaster to test.

Interestingly enough, thin plaster is surprisingly sturdy. It took several smacks with a metal hammer to get my test pieces.

And here are my candidate sealers; ScotchGard, furniture polish, matte varnish, dullcote, and wax resist. Off to the right is my control piece with my usual mold soap. I've etched a letter into the plaster chips so I know what's what.

At this point, all I wanted to know was which of these actually sealed the plaster. As it turned out, plaster is really hard to seal. ScotchGard doesn't seal it at all, no matter how much is applied. Surprisingly, neither did the DullCote, though the varnish did. Unfortunately the spray was strong enough that I suspected I'd never be able to use an insert to protect the design area from the spray. The only two "alternate" sealants that worked were the furniture polish and the wax resist. Of those two, the wax resist was both more effective and easier to apply, since it brushed on just like the mold soap.

Like I said, this is how I wasted a day in the studio. It probably wasn't necessary, although it was certainly interesting. After calling Joan to discuss my results, it became clear that my real problem wasn't that I was using mold soap, but that I was following the mold soap directions. (I tend to do this, much to my husband's frustration.) The instructions called for 8 parts water to 1 part soap. So yes, Sarah, my soap was simply too wet.

I still plan to make a comparison test. I want to seal one Imp mold with my soap (straight, no water), one with wax resist, and one with Joan's soap. I am pretty sure all three will work, but I want to know which one works better. And next time I'll just wait for the time difference (Joan is on the other coast), and use my "phone a friend" option!

Inside baseball

I hope the blog readers can forgive me if I engage in a bit of mold-making "inside baseball" for a moment. This is all a bit off in the weeds, even for those of us who make plaster molds. But after speaking to Joan Berkwitz recently, I discovered the reason behind a problem that has consistently plagued me. I have high hopes that now that I know why this happens, I can figure out a solution to stop it.

Let me explain the problem.

These are pictures of the two mold pieces that form Imp's raised foreleg. The piece to the left in the small inset (gusset) piece, and the piece to the right is part of the large side piece. The pictures aren't as clear as I might like (I'm pushing the outer limits of the close-up function of my camera here), but if you look closely you can see that the design area on the left hand piece looks dirty. There are small bits of clay still stuck in some of the crevises of the leg. The piece on the right is discolored from a very recent pour, but there isn't any actual clay left behind. The leg separated cleanly from the mold, which is what it should do.

I've had the same problem with the inside leg pieces of the Al-Hadiye mold. In fact, the problem has been worse than the one with Imp.

Obviously this kind of thing makes for a lot more cleanup work on the 'stuck side' of the leg, which is the last thing you want with a really thin leg. But the real problem is that because the clay will not release properly, it tends to pin the leg into the mold. That's why Al-Hadiye is such a high-loss mold. Those front legs almost always get pinned, and then break as the mold is disassembled.

What I found puzzling was that the first pour in both molds came out reasonably well. With Al-Hadiye, the loss rate quickly rose after that. With Imp, the problem was less severe but there was an increase in problems with that leg as the mold was used. This didn't make sense to me, since usually castings separate from the mold more easily with time, as little rough spots get worn with use. That was the question I posed to my mentor, Joan. Why would I be experiencing the opposite problem?

Joan explained that inner pieces like these gussets have problems because they don't have enough plaster area to absorb the water from the slip. If the mold cannot pull enough moisture from an area of the casting, it doesn't dry enough to release - or at least it won't until the other parts of the casting are so dry that they break during the demold.

These pictures of the Imp front gusset (top) and the Al-Hadiye middle gusset (bottom) show just how little plaster there is to absorb the water. And with Al-Hadiye, the situation is worse because he has two legs side-by-side, both needing to lose their moisture. No wonder he is so problematic!

But when I mentioned that the legs were leaving a film of clay behind on these parts, Joan said that was more typical of getting a bit of sealant on the design area.

We have to use sealant on these pieces to get the plaster to split apart after each mold piece is made. That's why the size of the plaster inside is such a problem. The other surrounding plaster pieces cannot take that excess moisture because there is a barrier - the one painted on the inner pieces to allow them to separate later. The only plaster available to draw the water out is what is on that one sealed piece.

Because it's so important not to get sealant on the design area (that water has to leave the casting there), we paint it on by hand. Joan thought that perhaps I had gotten some small amount in the design area, because the "dirty" effect that you can see on that inside leg is often indicative of that. The problem was that I just couldn't see that happening, especially not with each and every mold. I am too darned fussy about how I work. (A trait that is both good and bad, I'll readily admit!)

So I puzzled and puzzled over this, until I had an epiphany. Joan was right. I did get sealant on the inner design. But not the way one might imagine. I wasn't accidentally painting it into the design. It was seeping into the design from behind. We use mold soap to seal the pieces, and that soap is dissolved in water. The first few coats soak into the mold piece, and eventually build up a water-tight barrier. With less than 1/4" of plaster, no doubt I was probably soaking that sealant through the back of the design.

And even if I didn't reach the design this way, I was still sealing up some ability of that plaster to absorb. And I didn't have any plaster to spare!

So this is now the problem I need to solve. If I can't find a way around this, small-scale horses with side-by-side legs (like Al-Hadiye) are not feasible (perhaps in some cases not even possible) to cast. And all but the most simple of pieces will have a high loss rate.

Of course, imagining how cool certain horses would look in ceramic is a serious motivator. And I have some ideas already. My first plan of attack is to see if there is some way to seal just the surface of these pieces, without anything soaking into the plaster. I just wish - for the hundredth time since taking up ceramics - that I had a stronger background in chemistry.

Thursday, January 22, 2009

Not again...

I swear Vixen is cursed.

First I pulled the mold walls in too closely (top middle). That wasn't going to work, but I thought I could salvage the work by making adjustments in clay, pouring the second side and then repouring a corrected first side (top left). That didn't work. Actually, it would have worked but in doing this I realized that my mold was backward from the start. So I clayed her right-side-up and made the third attempt (top right).

I thought that since she'd already proven to be a troublesome little mare, I would be really sure to give her a good coat of release agent. I'd had some trouble with Imp because I been too sparing with it. I was able to get the resin out from the rubber, but not without snapping his tail. It wasn't a big deal, since the resin would only be used from that point on as a reference when cleaning the castings. I just glued his tail back on and all was well. My fear was that if the resin Vixen became trapped in rubber, what might break would be a leg. And after all that had gone wrong I had no confidence that I would only need her again as a reference! So I gave it all a really good spray.

Apparently too much. A few hours after the pour had set, I went to lift the mold box so I could set it out of the way and Vixen, still nestled in her bed of clay, slipped right out from the bottom. I've never had that happen before! Usually the resin and rubber seal pretty tightly. And in this case the rubber hadn't fully cured. In my experience, if the original comes out really early then the impression in the rubber tends to soften just a bit. And that is exactly what happened. So today I will pour the first rubber piece on her... again. Perhaps the fourth time is the charm!

And it might not be the last, either. I think my problem was an excess of release agent, particularly the amount I sprayed on the interior of the Legos. But if you look at the three rubber pieces, that last one is much darker than the first two. My rubber is now a month old, and those containers have been opened repeatedly, so it has begun to degrade. This next pour should tell me which was the source of my problem.

I cannot complain though. I got really lucky when molding Imp - far luckier than I should have been. If Vixen had been easy, too, I might have gotten too cocky. If there is one rule in ceramics, it is that the medium conspires to make sure that never happens!

Monday, January 19, 2009

A clever tool

I thought I would share some of the problem-solving that has gone into making Imp in ceramic. Each horse presents different production challenges. In the case of Imp, most of them have centered around his size. Just a few years ago, we thought stablemate-scale sculptures with thin legs were not feasible. That's one of the reasons there are so many draft and pony breeds in ceramic; they have relatively thick legs. (Well, that and many of us working in ceramics are Anglophiles.)

We have gotten a lot better at dealing with thin legs, but problems remain with small horses. When earthenware horses are cast, liquid clay (slip) is poured into the mold, allowed to sit until a skin is formed, and then drained back out. As a result they are hollow inside, somewhat like a chocolate Easter bunny.

The goal is to get a fairly even thickness to this "skin". Excess slip can't stay inside the body of the horse or the barrel and hindquarters suck in during the drying period. Those larger areas must drain back through the pour hole. This means that the pour hole opening has to be large enough to drain the slip even after the skin has formed around the opening.

With most horses, this isn't a big problem because they aren't poured very thick. Imp is different in that he must be poured a little thicker, otherwise the area around his throatlatch closes off, leaving an air pocket inside his head. Air pockets that don't vent to the outside can cause a piece to explode. The idea of opening a kiln to find a half-dozen Imps with their little heads popped off was really unappealing! The solution was to wait longer to drain him so the inner walls would be thick enough to make his head solid.

The problem with this was that his pour hole - the spot where the clay had to drain back out - was already too small. His belly just wasn't wide enough to hold a proper sized pour hole. Walls thick enough to fill his head closed off his pour hole, but weren't so thick that there wasn't excess slip sloshing around in his belly. I needed to be able to clear the pour hole so it could drain.

Unfortunately just sticking something up inside doesn't work well. It's hard not to push through the pour hole and on into his back. Since the mold turns upside down to drain, the damage to his back would not refill. What I needed was a special tool just long enough to clear the pour hole, but too short to hit his back.

I needed something that could scoop the clay out of the opening, rather than just push it around, so I used my round-nosed pliers to make a loop from some armature wire.

Here I've used the rubber master to determine the length needed. I want the loop far enough inside that I'm not scraping it against the plaster mold. The metal wire is hard enough to chip the plaster. I want it just a little beyond the opening, but well away from the topline.

After marking the length I need with a Sharpie pen, I bent the remaining wire into a handle.

Then the handle was covered with polymer clay and baked. This stablized the handle and allowed me to hold it a little better. (The purple handle has also make it harder for me to lose the tool, which has made me wonder if I should paint all my tool handles bright colors!)

Since making the draining tool, I've been getting a higher percentage of Imps that survive to the bisque stage. Now my only production question is if I can get them to the final glazed stage.

Thursday, January 15, 2009

Some cool horses

I've been busy catching up on neglected tasks and cleaning out the studio, hoping that clearing out the clutter (both the literal and mental sort) will improve productivity. So I don't yet have a glazed Imp, but I thought I would share pictures of Jag. He's the new horse at the barn where I keep my mare, Sprinkles. He has a really fun personality

He's also most likely carrying the splash overo gene. It might be hard to see in this photo, but this right eye is partially blue. His muzzle is interesting, too, because that isn't mottled skin. It's actually white hair on dark skin, and it only appears on this one side. The other side is dark.

My camera had a hard time capturing them, but he also has really pronounced reverse dappling.

Jag has had me thinking about how much the horse world has changed in recent years. He brings the number of appaloosas at our barn up to five. We also have four pintos and six palominos, but only three bays. For years the common complaint in the model horse community has been that we have a disproportionate number of "odd" colors, unlike the real world where most horses are bay or chestnut. It does seem that this has been changing somewhat.

One of my favorites at the barn, Omi, is bay. Despite his advanced age (28), I suspect I don't have to tell anyone his breed. He is still used regularly as a lesson horse, and has the most amazing trot. I hope I age this well!

Like my own mare, he's hard to photograph because he's a love sponge. I have a lot of pictures of the end of Omi's nose, instead of his neat tipped-in ears, because he always scoots in closer right before I snap the picture.

The presence of clutter in my studio (and my life) undermine my productivity, but spending time among horses is absolutely the best thing for it. I purchased Sprinkles almost three years ago because I thought unlimited access to an anatomical model would be helpful in my sculpting. What I didn't realize then was that being around horses on a regular basis would help almost every aspect of my work.

Wednesday, January 7, 2009

Palm pony!

This is the first bisque Imp. As you can see, he is tiny enough to fit entirely in the palm of my hand.

Because unfired greenware is gray rather than white (or transparent amber, in the case of the rubber), I was able to see all his tiny details. He even has a faint facial vein! I think you can see it in this close-up. How Sarah manages to sculpt this small just boggles my mind.

His only flaw is that he tips. I am going to pour a few more to see if they all end up tippy, but since his legs are properly aligned I suspect the bisques just have a slightly different balance. (Mel, for your sake I won't use the B-word.)

Monday, January 5, 2009

Christmas by the sea

As I mentioned in a previous post, my mother retired this year. That meant it was time to make good on a family promise that once she left retail, we would celebrate by going to Florida for the holidays. (The was the first time my mother was not working on Christmas day in more than thirty years.)

So finding this wreath-like bit of sea debris washed ashore the day we arrived seemed like a good omen. I was rather tempted to briefly borrow one of the red bows on the garland decorating the condo complext where we stayed, but I didn't want to get labeled as a trouble-maker on my first day, so I had to settle for taking a few bows off the presents we brought. My husband thought the fact that I was concerned about the proper color contrast was proof that I needed to spend a week away from the studio!

I am not really a beach person, but there is a lot to be said for 85° weather in December.

I was also amazed at the number of birds, many truly oblivious to the people around them. This guy was a regular fixture on some old pilings at the end of our beach. We have cormorants here; in fact, we see them so often when we are sailing up at nearby Lake Norman that the boys have dubbed one of the islands there "Cormorant Island". That island is a waterfowl preserve, though, so watercraft - even our environmentally friendly, silent sailboats - are restricted from getting too close. I hadn't seen them upclose before, and I was fascinated by their brilliant, emerald-green eyes.

The locals didn't share my interest. Several told me that they were considered pests, much like the seagulls. I did notice that, like the seagulls (and urban pidgeons), they had suprising variety in their plumage. That usually happens when animals are domesticated. It was amusing to think of a hint of domestication with something that looked, up close, so much like a dinosaur.

But as much as I enjoyed the birds, I missed my dog, my pony and my studio. By week's end, I was pining to make things.

Which lead me to make this mythical sea horse on our last day. I think I would have benefited from the widespread availability of the internet there in Florida to look up sand sculpting techniques, because I sure could have used some tricks for keeping the stuff together! I guess it would have also helped if I had some tools besides my hands and a plastic ice cream spoon. (I did like working in a medium compatible with popsicle-eating!)

And now I am home with all my favorite tools and materials - and a working Imp mold. The new year is off to a good start!

Sunday, January 4, 2009


It worked! It worked! Okay, so his little tail popped off, but he was otherwise fine. It seems Imp can be cast from a relatively simple mold.

I am not sure about his tail. With this one, I waited too long to demold him and he began to dry. I knew he'd dry fast, as small as he is, but I was way off in predicting the wait time. That will often cause breakage on the appendages, which is exactly what happened. I'm not sure, though, if the tail will work even if I pull him out sooner. I may be reattaching a lot of tails! But then I originally thought I'd be casting with multiple molds and piecing together a partial body, two legs and a tail. So I'm ahead no matter what.

In all other respects, the mold worked perfectly. Now the question is, can I clean him without breaking him? And, if I can do that, can I do it more than once in a blue moon? But for now, I'm just thrilled that I have one, tiny little raw mud Imp!

Oh, and we did just get back from our trip to the Florida coast. We arrived home late last night, too tired to unpack. I should have been unpacking this morning, but that untested mold just couldn't wait. I do have some fun pictures from the beach that I'll try to post here shortly, including my first foray into sand sculpture (I'll stick with mud in the future).