Casting, part one

Please remember, I have only had experience at Pour Horse, never took a class or anything, or worked at another factory. So the information I have is somewhat limited, but I suspect that these situations are universal.

First of all, you need a good mold. The mold needs to be clean, dry, and put together properly. Make sure that none of the pieces wiggle around, or fit loosely. If they do, take the mold apart and see if some bit of clay or something is between two pieces and is keeping the mold from fitting well. Make sure also that the "keys", "notches", "buttons", whatever you personally call them, are clear of debris and the pieces are in properly. If you have a piece that just won't fit tight, get it as good as you can, strap it or rubber band it, and then put some clay in the cracks around that piece. If you don't your slip will run out and the horse will not fill properly.

Then, you need good slip. If you bought it, you must assume that its maker did the important work for you and you only need to mix it to the consistency you want. First, before adding water, you must mix it well. Slip is weird stuff, it is "thixotrophic", and when it sits for a while it gels up. You need to agitate it and get it moving to see its real consistency. I like to use a regular drill, and on the end I have a "mud mixer" attachment. You can buy this at the hardware store, but don't buy the cheap plastic one for paint, if it bangs around on the bottom of the bucket a couple of times it breaks. Get the metal one, with a fairly long reach, and the best one has one blade that can be slid up and down the pole, using a hex key. This is excellent for using in larger and smaller buckets, and you will be glad to have it handy. If you don't have this, you need a really stiff plastic or metal spoon. Plastic is better, metal can rust and rust is our enemy. Stir and stir, particularly if the slip hasn't been used lately. Then you need to pour out the amount you are going to use right away. You need a kitchen strainer. (In this cast metal is fine, since they are stainless steel and don't rust.) A nice big one, with the little hooks for holding onto the edge of the pitcher, is excellent. Keep it handy also, so you won't be tempted to go without it. You'll find out why soon...

If you have a pitcher (like for iced tea or Kool-aid) that's great. You can use anything that will hold enough slip and that is easy to wash. I've used clean margarine tubs. The big Costco sized ones are handy, and any other tubs like them. Put your strainer over the pitcher (we'll call it a pitcher even if you are using a margarine tub, after all, I can't see you so you could be using anything!) Pour your slip through the strainer, and pour a bit more than you plan on using. If you don't know how much you will need, just pour as much as you can fit into the pitcher with room to add a little water and stir. After all, it doesn't go bad! You can always cover it or pour it back into the bucket later. Now, did you see any lumps that your strainer caught? Maybe not, if this is new slip. But later, when you have been using it, and the crusty edge drops off into the bucket, and you drop your contact lens in, and a fly comes by and lands in the bucket when you're not looking (think tar pits here) you will be glad that you strained it. Always strain it if you are in doubt about its lumpiness. If you don't, when you pour it, Murphy's Law says that the one lump will go up into a leg as it fills, and block the rest of the slip, so you will have a three legged horse.

Stir your nice strained slip with a clean rubber spatula. Feel the joy. Be at one with the mud. Think positive thoughts. Then think about food. Why? Because chocolate is important, but cream and soup are more important. You want your slip to be thicker than cream, but thinner than soup. They sell "viscosity cups" for this, but really you can get a feel for it fairly quickly, and you can learn to vary it according to the individual molds.  Minis need closer to cream, so that they fill quickly and can be poured out easily. (see chill lines under trouble shooting) Bigger molds, little bits and up through classic, can take a thicker brew. Really big molds, bigger than classic up through gargantuan, can take almost soup, and it helps in the long run for strength. However, if your individual mold needs it thinner, mark that on the mold with a marker pen, so you remember. If you are not getting full ears, for example, or are getting chill lines, your soup is clam chowder when it should be tomato bisque. Hungry yet?

Add water, if needed, a very little at a time. Add and stir. Check again. You shouldn't need much water for a commercial preparation. Dip your finger in and feel how quickly it runs off, and how much it coats your finger. Be observant, and learn from your castings. Your slip will vary in its ingredients so there is no hard and fast rule. Every gallon is likely to vary, too, so you need to make it right just before you pour it. A word to the wise, I like to get the slip ready the night before, thinning it as needed, and then cover it and let it sit overnight to use the next day. The water is more "at one with the mud" this way, and it doesn't get sticky. Don't mess with your entire bucket. Just do what you are going to use immediately in the next couple of days.

Now, if you feel ready... pour. Pour smoothly, pouring against the side of the pour hole and trying to allow a little room for air to come out at the same time. If you pour too slowly, you will get chill lines, so it is better to pour faster and fill up the hole if the hole is just too small to allow slip in and air out. Keep pouring at the same rate until the pour hole is filled to the top. Then, watch closely. See the slip level go down? That's because of the water in the slip that is being absorbed by the plaster mold. Top it up again. You don't need to be obsessive about topping it up, but you do need to keep the level of slip above the level of the hooves of the horse. If you are unsure about the level of the hooves, next time the mold is empty, mark the approximate level in marker pen on the outside of the mold. That way you will know for sure. Keep an eye on the mold, checking the level every couple of minutes. If you are as distracted and hopeless as me, try getting a kitchen timer and clipping it to yourself. That way you won't get on the phone and forget the mold entirely.

See how the slip that is next to the plaster is getting hard? It's stiffening because the plaster is absorbing the water.   You want that thickness to be somewhere between a nickel and two nickels. A nickel if it's a smaller horse, and two nickels is about your maximum. You can let the horse get thicker if in the past you've had trouble, but a really thick casting has its own problems. (see troubleshooting) Because you are topping off the level all the time, you can't really gauge the thickness, can you? So let it go down a bit, maybe half an inch, and then use a tool to cut a little piece out. This piece will give you an idea of your thickness. Remember too, that the thickness now will not be the thickness when it is dry. It will dry thinner.

When the slip crust reaches the thickness you want, you need to drain the mold. This can be done by turning it upside down over your pitcher, and letting it drain out. Be careful that bits of plaster and boogers don't fall into your pitcher or you will need to re-strain it. If the slip doesn't come out, or comes out slowly, you will need to take a tool and get up into there and give it more room to escape. See, if you are pouring slip out of the horse, air needs to go in to fill the space. Otherwise, the slip won't come out, or the worst cast scenario is that the casting will suck inward and collapse. You don't want that, so if the slip is not coming out or is slow, take a long thin tool and stick it up into the pour hole, to about where you think the inner edge of the pour hole is. They make tools for this, and they are great, but if you don't have that you can use a wire loop tool or something. I like this dental tool that is a flat blade on one end, and a little scooper on the other, the flat blade can get in there and cut through the crust without just pushing the debris into the mold. Everyone has something they are most comfortable with, and I've used a dozen tools looking for the perfect one. Anyway, you want to clean some of the hardened slip from the upper edge of the mold, inside the pour hole, and pull it out so that the slip has more room to come out. You can look down into the pour hole, and maybe see where the clog is. This is just something you will need to learn on your own.

Finish draining the casting, and keep it upside down. You can rest one edge on something, like a piece of wooden dowel or something similar. If you lay the mold down flat with the pour hole still down, the slip runoff will continue for a few minutes and can glom the mold to the table. If this happens, your casting can collapse because there is no air going in. At the least, if this happens, the inside of your casting will not dry out as quickly as the outside, and it may remain wet longer. So rest one edge of the mold on something, so that air gets in. What happens if you turn the mold over, and leave the pourhole up?  Nothing, if you drained it properly. But if there is still some slip in there, for instance in a leg cavity, it will slowly drain into the lowest part of the mold. That is usually the head, so your horse will have a solid head. Much better to leave it inverted.

Now go have some chocolate. Better yet, send some to me.

Come back in a couple of hours. Turn the mold over and feel the hardened clay that's still in the pour hole. If it seems stiff, you can carefully remove the first piece of the mold. First, gently break the seal by lifting the first piece slightly, and make sure that none of the inner pieces show a tendency to come up with it! If it doesn't want to lift off yet, the piece is probably a little too wet. Give it another hour. If it lifts off easily, then continue to remove mold pieces. If the horse seems too wet to touch, you can leave it laying in the mold for a little while, but keep checking and don't leave it to go see a movie. The exposed part of the horse is going to dry more quickly than the part still in the mold, so you need to just let it stiffen enough to finish demolding.

This is really long, so the next post will be a continuance of this...  Joanie