Tuesday, November 25, 2008


My friend Thumper, trying to convince me that he is actually a bunny resting in the fall leaves.

My rubber Imp came out almost perfect. Not a single bubble marred his tiny face or heavily textured coat! He was, however, completely missing his tail. So I can conclude that my clever trick for surface bubbles was working for me. The same cannot be said for my grasp of sprue placement. Doh!

I thought about cutting the missing tail sprue and pouring another rubber this morning, but decided it was time for a break. We'll be spending the Thanksgiving holiday with my in-laws, and I've been playing in the studio when I should have been packing. (The last time I did this, we had one child who packed a suitcase full of Legos instead of clothes.)

When we get back, I'll pick up where we've left off. In the meantime, I hope everyone has a lovely Thanksgiving filled with food and family.

Monday, November 24, 2008

Making the rubber original

I don't spend much time in the studio on the weekends. Even if I tried to hide out in there, my family would come find me! (Especially when I have told them that no one gets to jump in any leaf piles unless I get to go first.) But I did get the master mold prepped so I could pour the rubber original this morning.

Mostly that involved hitting everything with mold release and cutting sprues. Plaster molds don't usually need this, but without sprues my rubber original will come out missing some body parts. I'm a little skeptical that even with these everything will fill correctly. Imp has a lot of narrow places!

So here are all the pieces so far: two sides, one poll and one gusset. Eventually the gusset will be cut into two, or perhaps three, pieces. I will leave it alone for now so there are fewer mold lines on my rubber original.

That original was poured early this morning, so now it's just a waiting game to see if I have a whole foal in there. I don't want to open the mold too early because the rubber can distort if it's disturbed before it fully cures. I'm trying to tell myself that I can go away for the holidays without looking, just to be sure it's done when I open the mold. (That's unlikely to happen. I'm never that patient!)

Sunday, November 23, 2008

The last pieces

Now that all the rubber has cured, it's time to take the Lego boxes apart. I tend to pour the rubber so that the last few hours of curing happen in the middle of the night, or while I will be away from the house, because I get impatient to see the mold and want to unbox it too early.

Here it is so far - the two large 'framework' sides and their plaster supports. The light brown oval on the top is the clayed-up poll piece.

Here I've used rubber bands to hold the framework pieces in place. These bands don't exert a lot or pressure, because I don't want to risk distorting the mold. Mostly they are there to ensure that the pieces don't slip apart later when I am pouring the inner pieces.

Now I can remove the clay which as been acting as a placeholder for my inner pieces.

Because the foal has a textured coat, and because his small size made this opening rather tight, I had to disassemble the mold to clean clay the remained on the original. Now that the mold and original are clean, I'm ready to add my pour hole.

Like the inner mold pieces, the pour hole is formed with clay. Because ceramic molds need a relatively wide "mouth", the pour spout usually extends to each side of the gusset opening which splits the gusset into two pieces - front and back. (You can see this typical pour hole opening on the Finn mold in the previous post.) Imp presents a bit of a problem in this regard because his left side legs are too close together to run the pour hole through them. Instead, as the picture to the right shows, I've run it off to one side.

I've also chosen to make this pour hole more uniform in width. That's because - for this mold at least - I'm only using this inner piece configuration to pour my rubber insert foal. Because I'm lopping off some legs, I need a few extra steps before I arrive at my final "mold of a mold". If I were working on what would be the final plaster mold, I would need a wider mouth to prevent clogging, but I'm going to take advantage of the fact that I can use something smaller for now. (This will all make more sense as we get to those steps - or at least I hope it will!)

Here I have poured the gusset. Once it is set I will flip the mold over and pour the poll piece. I don't have to wait until the first piece truly cures, just that it be set firmly. (This process is pretty messy, as this picture shows!) Since I am going to experiment a bit with my mold, I plan to pour more than one gusset piece. That way if something I try doesn't work, I will have a replacement piece without having to set up to pour again.

With luck I will be able to pour the rubber insert on Monday. I have an idea I want to try to see if I can get a more faithful (mostly bubble-free) casting, and I'm anxious to see if it will work!

Friday, November 21, 2008

From the comments

Becky Turner had a good question in the comments, so I thought I'd answer it here where I could use pictures.
"Im curious bout something.. why cant you pour the rubber copies from the original mold? cant you coat the original rubber mold mold with mold release and cast the rubber your using into it? if not..why?"
I believe Becky is speaking of the original rubber mold that would have been used to cast the foal in resin. I'm not using that mold because the mold lines for the ceramic version will be different from the resin one, and the pieces of the mold are actually as important as the original inside it. That's because while the rubber original (which I'll pour when all these pieces are done) defines the contours of the foal, the rubber mold sections define the contours of the mold pieces. I'm not really making a mold of the foal so much as I am making a mold of the mold.

What I am doing with all this clay is essentially sculpting the inner mold pieces. On the first side I was sculpting them in the negative - making the indention for that side of the inner piece to fit inside. Then on this last side I sculpted them in the positive.

You can see this pretty clearly on this Finn mold. The bottom piece was the first part was poured, when Finn was sitting on a relatively flat "bed" of clay. This might be easier to visualize if I flip the mold over here:

Imagine the blue area is the clay holding the horse for the first rubber pour. The white plaster is the first rubber piece made.

Flipping the mold back over again, now imagine that the yellow area is the rubber I poured in the first step. At this point in the process, that rubber is now holding the original in place. The blue area is the clay I used to form the gusset. (If I were to turn this mold around, you would see another blue piece where the poll piece goes.) The white plaster is the piece we just poured in our last step. You can always tell which side got poured first because it has a relatively flat horizon line, whereas the last piece has arcs. This becomes more important later, because plaster molds are designed so that a specific piece gets removed first.

I'll be pouring those blue inner pieces in the next steps. Right now the gusset is one large cavity, but I'll be adding a clay pour hole to preserve that space much like Sarah described in her recent blog post here. (Love the toothpick trick, Sarah!) Many times those inner rubber pieces get cut into smaller pieces, as you can see from the lines separating the front and back gusset into two sections.

The split between these to pieces was made by cutting the rubber after it had cured. If I was going to cast Imp whole, I would be doing this with his gusset pieces, too. Years ago, horses almost always had two gussets - one to the front of the pour hole and one to the back. With ceramic horses getting more and more detailed, multiple gusset pieces are now the norm. The downside to this is that legs often have three mold lines instead of two, which is one reason Imp will be cut apart and cast in pieces. If I put three mold lines on his little legs, there wouldn't be much leg left!

And finally, if anyone has questions don't hesitate to post them in the comments section. I might not be able to give a good answer, because I am still learning. But teaching others (even if you know only a little!) is a great way to learn more, so I will certainly try to answer.

Thursday, November 20, 2008

The last easy part

Ceramic horse molds all have the same general format. There are two big side pieces which have the left and right profile views of the horse. Those two pieces form the structure that holds a varying number of inner pieces. Unless the sculpture has ears that are pinned back or are hidden inside the mane, or unless the head is turned just right so that each ear appears in profile (this is true of many Hagen Renaker pieces), there will be a piece that sits atop the poll. And finally there are the inner leg and belly pieces. Because of my family background in textiles and sewing, I tend to refer to this group of pieces as the gusset.

I find that the two side pieces and even the poll piece to be pretty straight-forward. It's the gusset pieces that are the challenge. This time around, I've added a new level of difficulty because I'm going to eventually cut this little guy apart, which will change how I approach those inner pieces. So this second side piece is going to be the last easy part. After that, the project is likely to get interesting because I'll be making it up as I go along! (Perhaps I should have thought about that before I decided to blog this all in real time, huh?)

But I can put off those thoughts for a little while yet, because at this point all I am after is a rubber copy of my little guy. That means the mold I am making for this step can have fewer inner pieces, because everything involved can bend. (Plaster isn't nearly so good in that regard!)

There was something unusual with this side, though. In most molds, the insides of the legs are contained in the gusset pieces. For this piece, however, the one hind leg was pulled back far enough that part of it could appear on the side piece. What stumped me was just how to plane the clay between that part and the other hind leg. The clay needs to hit the mold line at as close to a 90° angle as possible. To keep that angle at the back of that nearest hock, and still have the side piece pull off clean, that inner piece was going to have to have a tiny lip and then slope dramatically, all across a tiny space (1/4").

I haven't done any molds with inner leg pieces included on one of the sides, but I knew Joan had done that with the Okie Rio mold. I had a sample one here, so I looked and sure enough that mold had the same solution - a thin edge to preserve the needed angle against the casting, and then a quick drop. I used to love having some of the old Pour Horse molds because it meant I could glaze a few of those pieces. Now I spend more time studying them than casting from them!

Imp will also require a small inner piece to catch the detail under his tail. These kinds of pieces that don't extend out to the edge of the side pieces don't appear in the master mold, but are made by hand for each individual plaster mold. That's one more thing I can put off until later!

Here my clay mock-ups of the inner pieces is just how I want it, and I've begun to smooth the clay so there are no rough edges between my plaster pieces. (Everything in front of the foreleg has been smoothed, while the area behind it has not.)

The lines where the legs meet the body are where I propose to cut the legs. These will be removed and cast separately, then reattached when the foal is in the greenware stage. There is one other visible mold line near the top of the foal's head. One of the cardinal rules of ceramic mold making is that you do not second-guess and change your mold lines during the claying up. Obviously, I broke that rule! But I knew when I drew that line that I might revise it if it looked like I had it set too far, which I had.

With luck I will finish smoothing these pieces and get the second side poured today. My goal is to have the whole master made by the weekend, and have a rubber original or two by mid-week. That way I can spend the long ride to visit my in-laws thinking about how to tackle the next steps.

Wednesday, November 19, 2008

Why Lego mold boxes are cool

This is going to be another long post, but this is where using the Lego mold box gets fun. In the last part, I had my marble (well, bead) keys made. In this picture I've added another layer of Legos and poured a thin layer plaster over the rubber. The plaster will serve as extra support for the final mold, making it even less likely that the design will distort. The keys I created on the back of the rubber will hold this plaster piece in place. (The molds in this post have plaster supports top and bottom.)

Here I've taken off that extra layer of Legos to expose part of the plaster support. I don't want to expose it all, since the mold box is going to help hold the plaster in place for the next step. Notice that I took the mold off the green laminate board after my rubber set up.

That's because from this point forward, I'm going to be flipping the Lego box over a lot.

Here I have the upside-down mold box with the plaster support partially exposed. This will let me sand the plaster support level and round the edges and corners to prevent chipping.

Here's my leveled plaster support. I've also replaced the layer of Legos I took off before, so everything is the same as it was at the start of this post. (Except that my mold will now sit flat on the table when it is finished.)

Now I'm going to flip the mold box upside-down again.

Sometimes I can grab a bit of clay and all the clay will pull free. It didn't work so easily this time, probably because the foal is textured, so I remove layers of Legos until I can see the area where the clay meets the rubber.

Here I am lifting the clay from the rubber piece I poured yesterday.

This is where the Legos come in. The second side piece will pour against this first piece. The normal procedure would be to unbox the first mold piece along with its plaster support, and then rebox them for the second pour. But Legos can be added to what was the bottom - now the top - of this mold. They just have to be built upside-down! But there is no re-boxing, so everything remains sealed.

This is time saving, of course, but it's particularly helpful with really small pieces. The less the rubber gets disturbed, the greater the chance the original remains sealed in place. If the seal hasn't been broken then excess rubber cannot seep between the original and the first mold piece, which means one avenue for distortion has been closed off.

I've removed most of the clay in this picture. I haven't bothered to dig out the area between the legs - in fact I placed those pieces in sections so they would remain after the perimeter clay was pulled off. I'm going to have to clay those areas during the next step anyway.

I've started to clay in my inner pieces, which get poured last. I've started to build my Lego wall where I have the clay, but I've left most of the wall off for now so it's easier for me to work. When the inner mold pieces are clayed up, I'll add the rest of the wall and pour the rubber.

That flexibility is why I find the Legos so useful. I can build my mold box in either direction, depending on what piece I need to make. I can also put part of the mold wall in place if it's helpful, or take part down, depending on what I need to do at the moment.

I lost my marbles (literally)

When I was a kid, one of the most common things to hear my mother say was, "Is nothing sacred!?" She would say this when something - usually her nice sewing scissors - of hers went missing. The assumption was that one of us kids (usually me!) had borrowed the missing item.

Yesterday, I caught myself sounding just like my mother. I didn't forget the setting rubber for a change, and was there at just the right time to add the marbles. Only there weren't any marbles. Someone had borrowed them. Or I lost them. (Now I see why my mother never seemed really angry when she complained about our rather vague notions of ownership; she couldn't rule out the possibility that she had misplaced the thing herself!) I ransacked our house, and could only scare up two small marbles.

That wouldn't give me enough keys to hold the plaster backing, so I scrambled to find something - anything! - round. That's when I found the extra Cub Scout recognition kit I purchased last year. (Tiger Cubs are forever losing those achievement beads, so I wanted to have plenty of replacements.) Those big beads were just about the same size as a small marble, so I thought they might work in a pinch.

Not only did they work, they were better than the marbles! The hole through the middle meant I had a place to pry the bead loose once the rubber cured. Even more important, the slick plastic surface didn't bond to the rubber, so the beads came out clean. You can see the the tears around the two right hand keys where the marbles bonded to the rubber. Marbles have surprisingly porous surfaces, so I lose a portion of them with each mold when they become permanently gunky with rubber. The beads came out clean, so I'll be able to reuse this same pack of beads each time.

Tuesday, November 18, 2008

Pouring the first side

I finally have Imp all clayed up. I've checked to make sure I haven't missed any undercuts and that I've followed my mold lines faithfully. You can see I've cut in natches - the indented circles around the outside of the clay. Those create keys so the mold pieces don't slip during use. At this point he's all ready for me to pour the first side of the rubber mold.

These are the essential tools for rubber mold-making. No matter how well I mix my rubber, what's left on the rim of the bowl and the spatula never cures. (And what does cure never comes off!) So I stock up on throw-away food containers and rubber spatulas at the local dollar store.

I use a polyurethane rubber that comes in two parts which have to be mixed in a 4:1 ratio. Normally I would do this mixing outside - instead of on my dinner table - since I dislike the smell of the rubber as it cures. Unfortunately for me it's only 37° outside, which is too cold for the catalyst to work properly. (I had to learn this the hard way a few years ago. You end up with something that looks and feels a bit like school paste, only it never dries.)

Here I've just added the catalyst, which is a golden brown color. Once cured, the rubber is translucent amber.

I start by pouring a small amount of rubber and then tipping the mold around so the rubber flows around the original. What I want to do is make sure no air bubbles get trapped in the detail of the original.

In this picture I have moved the rubber around enough that the entire design area has been covered with a thin layer that is relatively bubble-free. Now I can safely pour the remaining rubber into my Lego mold box.

The original is still almost visible there inside the translucent rubber. The challenge at this point is to come back in an hour or so and add the marbles to key the back of the mold. I often forget until it is too late and the rubber has cured enough that the marbles won't work. I am setting the timer this time, so maybe I won't have to cut any keys.

Monday, November 17, 2008

Nothing is more valuable than a good mentor!

After posting the in-progress pictures for Imp last week, I was contacted by my long-time mentor, Joan Berkwitz. She pointed out that I could reduce the amount of displacement of my inner mold pieces if I tightened up my mold perimeter. She was particularly concerned about the size of the inside ear piece (the "Carmen Miranda hat").

So using Joan's markup, I dramatically cut down the size of the mold. Oddly enough, what I ended up with was pretty close to the original perimeter that I had laid out, and then enlarged at the last minute. I had worried about leaving enough plaster to absorb the water from the slip, since I had recently made a medallion mold with too little border and knew the problems that created. What I hadn't considered was that while the medallion and the foal weren't that different in overall dimensions (width, height, depth), the mass involved was dramatically different. The foal would dry evenly without much trouble. What I should have been worrying about was the shifting of the inside pieces.

So I have been reminded today that a good mentor is a priceless thing. I still remember Joan telling me, back when I first started making molds, that the best reinforcement for a lesson was cursing. If you overlooked something and it caused a disaster bad enough to set you to cussing your own foolishness, you were more likely not to do that thing again. I have certainly found that to be true! But sometimes having a good friend to warn you that what you are about to do will result in a lot of cussing is just as good!

Friday, November 14, 2008

More impishness

It's a good thing I didn't have to make good on my plan to drown my sorrows in blue clay, because Michaels didn't have any more blue. I had to settle for pale terra cotta instead. Here I'm just trying to fill in the gaps between the resin and the original bed of plasteline so the original doesn't shift when the rubber is poured.

This was also the point where I realized just how challenging this little guy was going to be. I already knew from my experience with Al-Hadiye that leg flexibility was a big problem. But that was with the rubber original. Little Imp here already has flexible legs. I found those little resin legs gave - and gave a lot! - against the pressure of the (relatively soft) plasteline. Yikes!

But he's so cute. And I do have all this rubber that will go bad if it's not used soon...

Here I've smoothed out the clay and have begun to shape the inner pieces. What I am going to be pouring is the large outside piece, so what I want here is to create an appropriately shaped negative area to hold those pieces.

That concept is more obvious in this picture where I have added the shape of the mold piece for the poll. Almost all horses require this piece so the ears don't get damaged when the horse is demolded. Claying up this piece always makes me smile because it tends to make the horse look a bit like Carmen Miranda.

Notice I haven't built up the walls of the mold yet. I want better access to the clay, so I don't want to have to reach inside. Once I have the clay just right, I will build up the walls.

Now that I have the basic contours right, I am ready to finish the surface. I'm using a soft brush dipped in a little oil to smooth the clay. I'm also making sure that I have hit my mold lines exactly and that the clay is flush against the original. This is also my last chance to double-check for areas that might catch in the mold. (I think all is well so far!)

I have a few more steps before I am ready to pour the rubber, but it's exciting to finally have him underway.

Wednesday, November 12, 2008


"Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has."
- Margaret Mead

Okay, so we didn't change the world. But we did convince the School Board to let us keep our school!

Now I can go back to my normal life as a maker of small horse-shaped objects. Which is good, because I'm pretty sure I wasn't meant for life as a political agitator.


I was going to spend the day glazing lottery pieces, but with the school board vote (tonight!) looming large in my mind I was really too agitated. I talked myself into the idea that even though the lottery is falling further and further behind schedule, everything here is pathetically behind schedule. Using that logic, I told myself that anything I worked on was a helpful step towards getting things back on track.

Designing the mold for Imp was just the mentally consuming puzzle I needed. There were a lot of issues to think through if I was going to make the project work, but nothing I did today couldn't be undone later if it proved to be a mistake. (And I could further rationalize the time spent by telling myself that molds take forever to dry, so if I wanted to be able to tackle making these guys when the lottery horses were done, it would be better if I did this now so they could start drying sooner.)

I don't have a lot to show for all that thinking, other than those inked lines on the little guy. They don't look like a lot of work, but deciding where they go is the biggest hurdle in mold-making. In his case, I have two possible paths to take. I can try to cast him whole, or I can cast some of his legs separately and then reattach them in the greenware stage. Given the trouble I have had with distortion on the Arabian's legs, I've decided to try the piecing-together route first.

But in order to do that, I've got to make a rubber master. (That was the last and final rationalization for veering from my plans: I have leftover rubber that is nearing the end of its useful life.)

Since Imp is so small, I'll be using Legos to box these molds. Legos are wonderful because they eliminate the tedious sealing necessary with wooden mold boards. Here I've gone ahead and made a simple Lego frame to mark off the dimensions of my mold. The green background is a small square of countertop laminate. (I had my husband cut these from the scraps left when we redid our kitchen a few years ago. They make wonderful non-stick bases for molds.)

Here I am adding some Plastelina so I can start to clay up the original sculpture. The Plastelina is soft and smooths easily, and it can be purchased cheaply at the local Michaels, so it's perfect for this. I like this pale blue color because it shows up well against just about any material used for an original, although it reminds me of the blue icing they put on birthday cakes for little boys. (The texture isn't much different, either!)

Here I've placed Imp on his Plasteline bed. Once I have him positioned where I want him (keeping in mind that this is where the slipcast piece will be inside the plaster mold), I will begin claying up the original so that I can pour the first piece of the rubber master mold. That won't happen today, though, because I ran out of both Plasteline and time!

Perhaps tonight we will get good news about the fate of our school, and tomorrow I will painting with renewed enthusiasm. If not, I may be drowning my sorrows in sticky blue clay!

Sunday, November 9, 2008

More sooty oddness

This Morgan gelding, Sky, is the oddly marked sooty palomino I mentioned in the previous post. In this picture where he is darker, it is easy to see that his dark hairs form a pretty typical sooty pattern with the dark knees, dappling and ear rims. He even has the dark ridge along the leading edge of his cheek. If you look closer, though, you can see some slightly darker areas on his barrel and hip.

Those same areas are much more visible when Sky turns lighter. (Having been around a number of palominos in the last few years, I have found it interesting how dramatically their color changes with the seasons.)

The pattern of the dark hairs is very reminiscent of those seen on blood-marked fleabitten grey horses. It's also interesting that whatever is concentrating these dark hairs into patches, it hasn't disrupted the dappling pattern. That's also true on Prince (the horse posted yesterday), though he is much paler so his dappling - which is obvious in person - doesn't tend to show up in pictures.

Here is the other side of Sky, showing that his odd markings are not evenly distributed. That kind of asymmetry is typical in blood-marked greys, too.

Although it isn't really related to his odd coloring, Rebecca said that Sky had another unusual quality. He's a gaited Morgan. What a really cool horse!