Tuesday, January 29, 2008


I think ceramics is one of those fields that really favors patient people. My friends tell me all the time that I'm "very patient" - though admittedly they are usually making this comment after spending the day with me and my overly-exuberant youngest child. Maybe that kind of patience doesn't translate to waiting for things to dry. Waiting until molds are dry enough to use, and until castings are dry enough to remove, is terribly difficult for me!

So there are victims. This poor Finn got pulled out of his mold before he was dry enough, and his side collapsed. Things like that just aren't worth the time they take to fix, so I crumpled him up. Normally he would have ended up the scrap bucket, but I must have missed him when I was cleaning. I found him this morning. Doesn't he look so sad? Actually, he almost looks like a horse all curled up to take a nap... if horses had no bones, that is.

Monday, January 28, 2008

Silver gene found in Andalusians

It appears that the silver gene has been identified in the Andalusian. The stallion Arco Iris is said to have tested EE Aa N/Z, which would make him a red (bay-based) silver. If you look at his pictures here and the video here, he certainly looks like a silver. This is a cool discovery, since many believed this was not a color that would be found in Spanish horses.

The finished product!

Here is the first of the finished "Summer Storm" plaques. I wasn't sure how the plaque would turn out in an art glaze. It was really designed so that the horse would be glazed in a realistic color while the background would be finished with an art glaze. (The leaf texture is there to take advantage of how art glazes flow into the recesses of the design.) But I like the all-over art glaze after all.

The plaque also shrank quite a bit. I had already noticed that my current batch of slip had a slightly higher shrink ratio than past batches. Whereas before the shrinkage was negligible, the new slip (using the same recipe) had an overall shrinkage rate of about 6%. For some reason, though, this particular piece is shrinking around 9%. You can see the dramatic difference between the final piece and the first original here.

The finished one is actually one mold further from the original, since the mane was added to a casting from it, but that's still a lot of shrink for one generation of moldmaking. It took quite a few generations of molds to shrink the Celtic Pony medallion that far.

I'm not sure why the shrinkage is so different from the pony. Perhaps the fact that it's rectangular, or has less depth. Or maybe because it can be poured with thinner walls. The question does make me wish I had studied ceramics in school, rather than graphic design! But whatever the reason, it certainly will make reducing the design to ornament and then to pendant size easier.

In the meantime I will be learning this mold's idosyncracies. They all have them! How thick the slip, how thick the walls, how long to leave the drained casting in the mold... each mold wants something different. So you always lose a fair number of castings from the early life of the first mold. The trick is to write all the preferences down so you don't have to relearn it all the next time the mold gets used!

Saturday, January 26, 2008

A new profile picture

I had been thinking it was time to change the photo above the "about me" section. As much as I like my Okie and his blue eyes, he'd stared at us long enough!

So now a little pixel version of my dog Emma is up there. I started playing with pixel art when I was confined to the couch with a broken foot a few years ago. Recently I figure out how to animate them. Right now Emma is just panting, but I'm working on getting her tail to wag. (I'm too picky for my limited knowledge of stop motion imaging - I want it to properly swish!)

I promise to stop goofing off and have a proper shiny horse post on Monday, though!

Friday, January 25, 2008

My other job

This weekend I get to take off my potter's hat, leave behind my clay and molds, and become immersed in the world of little boys. That's because this year I'm a Cub Scout Den Leader, and this weekend is the Pinewood Derby.

My husband has been a Den Leader for years now, and my older son is a veteran racer. But this is my first year. I don't have the same skills to bring to the making of little wooden cars that my husband (physicist, son of a carpenter) does. Somehow knowing whether a horse is a splash overo or a sabino, and which underglaze can hold up to multiple firings just doesn't translate well. But I have a good digital scale and a signmaking father! And I bake well. So we'll be under the weight limit, ready to cheer for each other, and well-fed. (Nothing says, "It's okay, you'll win the next race" like a double-chocolate brownie!)

And my youngest son did have his father to help him make his own car. I'm not sure if you can tell with it in pieces there in the photo, but it was made to look like a paper airplane. With any luck, it will all stay together. I keep having visions of the airplane part flying off the base the first time it hits the bottom of the track!

So I'll be bringing tissues, too, in case anyone melts down. As anyone who has had even a passing involvement in scouting can tell you, the Pinewood Derby is a Big Deal. Not just for the kids, but the fathers. Oh my goodness, but you haven't seen anyone try to do-over their childhood like a man who wants his son to win the Pinewood Derby! I may well die of testosterone poisoning before the weekend is through.

Thursday, January 24, 2008

Getting back on track

Earlier this week, my grandmother took ill with what we thought was a bad stomach virus last week. When it became clear that it was probably serious, we left for Alabama. Later that day we learned that what looked like a virus was simply the early stages of renal failure. She passed away on Monday.

We just recently returned, and I am trying to get back on track here at home and in the studio. I have some new photos to share, so hopefully I'll be more myself in the next day or so.

Friday, January 18, 2008

First horse of 2008

This guy was the first horse out of the kiln for the new year. He's a rare custom order, donated to a benefit auction for Habitat for Humanity. I think he looks a little worried in this photo. Maybe he knows we are supposed to get more snow in the morning!

His color is a little off in these photos. In person he's more mousey and less tawny. I rely a great deal on the natural light in the house when I take photos, and there hasn't been much of that with all these storms. Hopefully I'll get the chance to get better photos when the weather clears.

Thursday, January 17, 2008

Mold inserts

I mentioned in the moldmaking post that I normally make a rubber insert for my medallion molds so I don't have to fill the cavity with clay. My new batch of rubber reached room temperature last night, so I poured one for the new plaque. [As a side note, you don't want to overlook the "room temperature" part of room temperature vulcanizing (RTV) rubber. Trust me.]

Here is the insert. I'm not especially careful about bubbles when I pour these, since all I need them to do is fill the cavity.

It's kind of fun to see him semi-transparent. They remind me a bit of the beeswax ornaments I saw on a visit the Plimouth Plantation. Too bad rubber doesn't smell like the beeswax!

This is the mold with the insert. All that's left is to box the mold and pour the lid. As you can see, the inserts leave the mold much cleaner than the clay. But mostly they just enable you to make multiple molds more efficiently.

Hot Chocolate and Dry Mittens

I had set aside today to take pictures of some newly finished horses, but it's snowing and the kids are home from school. Excited kids. Kids who haven't seen snow in several years. Kids too wired to be in the same house with ceramic horses. So we are all taking the day off.

I don't actually do snow. I hate the cold. There is no way I'm venturing outside to build a snowman. But I make a mean cup of hot chocolate (I have a whole jar of marshmallow fluff!) and I'm more than happy to keep a steady rotation of mittens in the dryer. I also have a lovely collection of old hats, scarves and carrot noses - for someone else to use.

Now if I could just find a way to hand all these things to them without opening the back door...

Thursday, January 10, 2008

Making the plaster production mold

In the last post, I described the making of a rubber master mold. This time I'll show how that master mold is used to make a working plaster mold. That is the purpose of the master mold; it becomes the mold for making a mold. One by one the rubber mold pieces are removed and replaced with plaster ones until the whole thing is replaced with a plaster version. So that's what we'll be doing here.

When I made the master mold, you might remember that I poured one of the large flat sides first. Once I begin making a plaster mold, that process goes backward. I will actually start with the smallest, innermost pieces and work my way outward. In the case of this mold, there is only one inner piece so I'll start there.

Here I've removed the inner piece and banded the mold back together. I don't need to box the mold at this point, because the rubber will contain the plaster. You can also see that the plaster backing on each side of the mold allows me to band the mold firmly without risking distortion of the inner image.

Here I have started pouring the plaster into the cavity.

As soon as the plaster begins to firm, I scrape it flush with the outer edges using a straight edge. Flush edges make it much easier to box the mold when the larger pieces are poured.

I only have to wait until the plaster has set and is solid. It won't be dry for another few days, but solid is all I need for now. Here I've taken off one side of the master mold (the one with the negative of the design) to reveal the inner piece. This piece will get a few coats of mold soap to keep it from sticking to the next piece, and then it's time to box it all up again.

(Oh, and it's better not to remove the plaster pieces after they have been poured if you can avoid it, since the seal helps prevent later pours from leaking inside.)

Here I am pouring plaster into the mold box containing the bottom half half of the mold and the inner plaster piece.

Here's everything so far, just released from the mold box. The thicker piece of plaster at the bottom is the plaster mold. The amber area in the middle is the rubber piece with the design (the piece we just poured plaster on to) and the thinner piece of plaster at the top is the backing. I'll be taking that backing off for the moment so the rubber has a little more give to it when I pull it from the production mold.

You can see from this picture that while the rubber does have some give, it's still pretty rigid. (You can also see that I missed my curing window for using the marbles on the back of this piece, and had to cut keys in by hand. Hate it when that happens!)

So here are the first two pieces of the production mold. All that's left now is the "lid". That's the piece that will fit over the top and will have a holes drilled for pouring the slip. Tile molds are typically open-faced so that moist clay can be pressed into the design cavity. Slipcasting molds need lids so the cavity can be filled and then drained. (That's why medallions and plaques are hollow, and tiles are solid.)

To make my lid, I'll need to fill the design cavity. Normally when I make my rubber master I pour an insert - a rubber version of the design - that I use for this. Unfortunately for this project, I ran out of rubber with the last piece of the master mold. So until the box arrives with more, I'm stuck filling it with moist clay.

I don't have to worry about getting a good casting - just with filling the cavity so I don't get plaster inside the design area.

Here I'm scraping the clay level with mold.

Now I'm ready to soap the mold and box it up so I can pour the lid. You'll also notice in these last few pictures that I cleaned up and rounded the edges of the mold a bit. That helps the mold fit in the mold box a little better.

These are the finished lid and the bottom half of the mold. The moist clay insert has been removed, but it has left a bit of a stain on the mold. Of course, the mold is going to look used soon enough, so it doesn't really matter.

The finished mold has had pour holes drilled into the lid (facing away from the camera) and then been reassembled, banded and left to dry for a week or so. I usually place the drying molds near the kiln, though not quite as close as in this picture. (The kiln was not running when this picture was taken, so I moved the molds closer to it so I didn't keep tripping over them.)

Now comes the hard part - resisting the temptation to pour slip into the mold until it is well and truly dry!

Tuesday, January 8, 2008

Making the rubber master mold

I'm probably making everyone dizzy, shifting back and forth between such differing interests as moldmaking and horse coat genetics. I need to figure out how to show subject tags to the bottom so everyone can organize my posts by subject instead of having them appear chronologically. Of course, that will only help if I get better about adding the tags in the first place. I usually forget.

But to get us back to making the rubber master mold for my new plaque, I now have my finished original ready to mold.

I've mounted the original to a glazed tile with a little Elmer's glue, then sealed the edges with a little clay (the reddish-brown edge around the design). That keeps the rubber from seeping under the original. The greenish circles around the design create keys so the mold pieces fit together without shifting.

With most medallion designs, there are just two pieces to the mold: the piece with the design and the "lid" that fits over the top. As you may remember from the waste mold made from the original piece, this particular piece requires an extra piece because of the undercuts around the muzzle. If you look carefully, you can see where I've drawn the mold line in pencil on the bisque. My next step, now that the piece is all set up, is to clay up that piece.

It's hard to see because the clay is dark brown, but I've added three natches to the insert piece. Each mold piece needs to have these so the final mold is tight and well-aligned. Now we're ready to box it all up and pour our first rubber piece.

I've used marbles once again to create my mold keys. The marbles are removed when the rubber is set (but not fully cured) and then a plaster backing is poured. The rubber and the plaster backing then remain in the clamped mold box for two days to allow the rubber to fully cure. After that point, the boards are removed and the plaster and rubber are banded along with the base tile. (The base tile with the design are still sealed in the rubber at this point.)

With the rubber, plaster and tile still banded, the clay forming the insert piece is then carefully removed.

Here the clay has been completely removed from the original. This step is much trickier when the original is made of clay instead of hard bisque like we have here! The original looks a little shiny because I had to spray the area with mold release so the rubber pieces separate later. (You only forget to use mold release once...)

Now I can pour the rubber. Like the larger piece, it won't be fully cured for another day or two so the mold must be set aside once again.

Here the cured mold pieces have been removed from the mold box. The circles with the dark edges are the keys on the back (the ones formed by the marbles) that hold the mold to it's plaster backing. The fainter circles along the top and bottom edges, and the three faint circles to the right side are the natches in the mold itself.

So we have two of the four pieces we will need - one large one with the design cavity and the smaller muzzle insert. All that remain now are the plaque itself and the "lid". To save ourselves a bit of hassle, we'll actually be pouring those two as a single piece of rubber.

Here I have poured rubber to fill the mold cavity and then up and beyond for several inches. (Think of the final piece as looking like the plaque sitting atop a platform.) In this picture the rubber has not yet set enough to place the marbles, and you can faintly see the outlines of the other mold pieces below. Once it sets a little more, the marbles are added and another plaster backing is poured. Then the box must be set aside for another few days so the rubber can cure.

And here is the final master mold. (I hadn't yet banded it when I took the photo. Normally rubber bands hold the layers in place.)

I know this post is already long, so I'll save the process of making working plaster molds from this kind of rubber master for a later post.

Friday, January 4, 2008

A Dominant White update

A few months ago I posted that a Swiss research team had identified Dominant White in horses. That article is now available online here. If you follow the link to the article and look at the horses pictured, you'll quickly see why some people have objected to the use of the term "Dominant White" for these horses. They look like ordinary sabinos.

The term Dominant White was originally used to designate pink-skinned, white horses with (usually) dark eyes. These white horses were thought to be the product of a single copy of the Dominant White gene. Since no Dominant White horse had proven to breed true, it was assumed that the homozygous form was lethal. What was not mentioned in early articles on the color was that these horses typically had a high percentage of broken-colored offspring. This fact, which was consistent across a wide variety of breeding populations, is what prompted me to write my original paper speculating that Dominant White was really just sabino.

It would seem now the issue is mostly one of semantics. What the Swiss research did not find was a gene that produced uniformly white horses. But at the same time, the genes that were identified (and they found four versions) do not behave the same as the already-identified Sabino 1 (Sb1). Sabino1 is the gene that American researchers found in some sabino whites. With it, white horses are homozygous and the broken-colored horses are heterozygous. Because not all sabino-whites carried Sabino1, it has been assumed that there were likely other (as yet unidentified) versions of sabino out there.

The Dominant White horses in the study were heterozygous. Some were completely white, and all were more than 50% white. It was speculated that, at least in the populations studied, the gene was lethal in the homozygotes. So the color does behave differently than Sabino1. For that reason I suspect the newly identified genes will not be renamed Sabino2, Sabino3 and Sabino4, as if they were other versions of the sabino gene. They will most likely continue to be called Dominant White, even if the horses produced are not exclusively white.

Of course, for those of us who paint horses, we'll probably come to think of Dominant White as just another version of sabino. It would be a version that tends towards the "whiter" end of the sabino spectrum, but aside from that the differences don't seem to be significant enough to matter, at least not for our purposes.

[Edit: I've included the illustration that accompanied the article, since some have had trouble accessing the page. I am often asked to post photos of the oddities that I have come across over the years, but I am unsure if what we do qualifies as "fair use" for educational purposes. So I'll include these photos, but be aware that they'll get pulled if someone objects.]

Thursday, January 3, 2008

Tobiano Arabians?

This mare is certainly stirring up discussions on a lot of the horse color forums, so I thought I would mention her here.

Normally I discount the designated breeds of the horses for sale on DreamHorse. Often what sellers do is list the breed the horse "most looks like", or perhaps whatever someone told them the horse was (or looked like). Sometimes I think it's just wishful thinking! But this seller has been very specific both on DreamHorse and on her own site that this horse is a registered purebred. It is even stated in the ad that the horse is "DNA typed, registered and confirmed purebred".

If you follow the link, you'll see that the horse is unmistakably a tobiano. (She is also a sabino, but that wouldn't make her unusual for an Arabian.) I think most people would agree that she's also unmistakably plain, especially for the pedigree that is claimed to belong to her. So it probably isn't surprising that many folks are calling foul, and that the registry has been contacted.

It may well be that somewhere along the line, papers were swapped and that mare is not really RWR Sonora. If so, the registry should catch the error when and if someone tries to register one of her foals. But if she does type out as Sonora (for whatever reason), then the truth is that tobiano will be in the purebred Arabian gene pool. To say that it would always be regarded with suspicion would be an understatement. But it would be there, and there would likely be enough breeders willing to take advantage to insure that it stayed there.

If I hear any more about the mare and her status, I'll pass it along.

Hair... long, beautiful hair...

Okay, so it's not exactly long. He is more or less a stock type horse after all. But he does finally have some hair.

Some of you may remember this guy from some of the earlier moldmaking posts. When I left off, he was awaiting a mane so I could make the master mold. As you can see, I added the mane in plastilene clay directly to the sealed bisque. Considering how much of a mess I made across the background as I worked, it's a good thing I was working on a bisque. If it had been the clay original, I probably would have had to recreate the background pattern. With the bisque it just took Goo Gone and a handful of sponge applicators and I had my background back.

Right now I am half-way through making the master mold. I've been taking pictures through the whole process, so I should have those to post in the next day or two.