Check out my video of the Iron Pouring Process here.
- Model-making. First, you’ve got to get creative. What do you want to create? Visualize your end goal, then sketch your ideas out a few times to see what might work, and what might not. For a first-timer, using ceramic clay is a great idea.
- Mold-making. Now it’s time to make your mold. Your mold will be made from your original sculpted model. 100% silicone is a great pick since you can buy it cheap from just about and local dollar store. You can either create a one-sided two-dimensional mold, or a three-dimensional mold. If you’re going three-dimensional, a shim with keys can be placed between the two halves during mold construction so that it can be put back together easily. Depending on how large your piece is, you might have to plan out how to recreate the original model, breaking your mold construction into pieces, especially for a large sculpture.
- Wax. So you’ve got your mold. Melt your wax and pour it into your silicone mold evenly. You can take this in steps, coating your mold in steps, or fill the entire mold with molten wax, and let it cool. Keep in mind, if you pour wax into the mold at once, it will take longer for the wax to dry.
- Removal of wax. Your wax copy of the original model is removed from the mold. Reuse your mold to create more wax molds. The more you models you have, the more creative an interesting the process can get. It’s good to make more than one mold; you never know when your creative spirit will hit you.
- Chasing. Use an electric soldering iron to clean up your wax mold or alter it. Blow dryers are good too with multiple heat settings if you want to hide any imperfections. Wax pieces that were molded separately can now be heated and attached; I won’t say easily because it depends on your mold. In combining your molds, you are only limited by your imagination.
- Spruing. Now, using more wax, your mold will be sprued with a treelike wax structures that will provide paths for molten metal to flow through and air to escape. I found that those tall candles that you can buy from the dollar store for your dinner table work well for this. During spruing, you can take a Styrofoam cup and use a wax candle-like form to attach the cup to the mold to give a pour spout that the molten metal can be poured into easily. A great way to ensure that the cup does not get slurry in it during the next step is to use any brand of aluminum foil and place it over the top of the cup, and secure it by dipping the cup with the aluminum on it in the wax and let it hard, multiple times. It doesn’t matter if wax gets in the cup because the wax will be melted out later in the process.
- Slurry. After spruing up your wax mold it is dipped into silica slurry; remember to weare a good face mask so you don’t breathe in the particles. After dipping the mold in silica slurry, then dip it in sand-like stucco, or a dry crystalline silica (of the same grain size.) Now you have created your ceramic shell mold material, although it is not literally ceramic, it just gets hard like ceramic. Let the shell dry, because you will dip your mold again until you have at least a half-inch coating that covers the entire piece. The bigger your piece, the thicker your shell needs to be. Do not get slurry inside the cup flat top because your cup holds the piece up. If you get slurry in the cup you will have problems during the next steps.
- Burnout. The ceramic shell-coated piece is placed cup-down in a kiln. The heat hardens the silica coatings into the shell, and the wax will melt and run out of the shell. Remember that the melted wax can be recovered and reused, but many times it is burned up. Now, what was wax in the inside of the shell and sprues is negative space that is necessary for the molten iron to occupy.
- Testing. Optional process where you allow the ceramic shell to cool then see if water will flow through the feeder and vent tubes as necessary. Any cracks or leaks that you find at this time can be patched with thick refractory paste.
- Pouring. The hot ceramic shell is removed from the kiln then placed cup-upwards into a tub filled with sand or dirt. Metal is then melted in a crucible in a furnace and poured carefully into the shell. It’s important not to let your shells cool off too much before pouring the metal because if this happens your mold shatter. After pouring metal allow your cast to cool.
- Release. Hammer away your ceramic shell with a hammer, but be careful; some metals are more pliable than others. You can ruin your hard work if you are not careful. After hammering, you can sandblast any excess remnants of the ceramic mold. The sprues, which are also faithfully recreated in metal, are cut off, to be reused in another casting.
- Metal-chasing. Now, you can cut off any remaining sprues with a grinder and recycle them for the next casting. Now your casting looks like the original model. Pits that were left by any air bubbles in the casting, and any sprue stubs can be filed down and polished.
Notes: The top image is an example of a sprued up wax mold that is ready to be dipped in slurry.
The bottom two images are the finished cast iron sculpture.