Much of the equipment you need to make hand-milled soap is the same as for other soapmaking techniques. But you'll also need a few other items, including graters, food processor, double boiler, slow cooker, microwave oven, spoons, scrapers, bowls, molds, and scoops.
The first thing you need to do in hand-milling is shred your soap. Of course, if you want, you can buy soap already shredded, which will save you a step. But this will limit your options. You need to look at what kinds of shredded soap are available. If you can't find the kind of soap you want already shredded, you can probably find it in blocks, so you'll need to shred it yourself.
To shred blocks of soap, you can use a simple cheese grater and elbow grease. Some soaps are harder to shred than others, so the amount of strength needed will vary. Be sure to take care you don't grate your knuckles as you work.
Use a grating surface that has the larger, approximately ∕-inch, holes. The tiny holes will take forever and produce soap powder, not shreds. (If you want to make soap powder, make shreds first, and when they're very dry, pulverize them in a food processor or with a mortar and pestle.)
Here's how to shred your soap. Hold the grater firmly over a container. Wear heavy-duty gloves or an oven mitt on your hand holding the soap. Draw the surface of the soap over the surface of the grater, using even pressure. The soap may start to collapse as the bar gets smaller. If this happens, just roll it into a ball and keep shredding until there is no more surface area. You can use any stainless steel tool for food again after you've used it for soap once you've thoroughly cleaned it. Consider, though, having some tools just for soaping if you use them a lot.
A much faster way to shred your soap is to run the bars through a food processor. You need to be sure your processor has a heavy-duty motor and enough room in the work bowl to accommodate the shreds without compacting them. Select the grating blade with the larger holes. Push the soap through the feed-tube as you would cheese.
You can often find used food processors in thrift stores and online auctions after the holidays. Always follow safety procedures when using any appliance. Some soaps may be too hard to process in a food processor. Take care not to learn this by burning out a motor! Refer to your food processor's instructions and look at the directions for grating cheese. Use this as a comparison guide.
You will need something in which to melt the soap shreds. Many soapers swear by slow cookers, but others wouldn't think of hand milling without a microwave oven. However, the most common method is with a double boiler. To use the double boiler, you place the shreds and the liquid in the top of the boiler, place water in the bottom, heat the water to boiling, then turn the heat down to simmer. As the soap melts, you add scent and texture materials. You must watch carefully so the boiler doesn't boil dry!
With the slow cooker, the process is not unlike making a rich stew. You place the shreds, liquid, and color in the pot, turn it on and wait for the low, steady heat to do the work. You can use the same slow cooker for hot-process and hand-milling techniques.
You need to watch the level of water. Soap can scorch if it gets too hot without enough water. If you find that your slow cooker dries out the soap mass, increase the amount of water in the recipe at the outset.
You can find inexpensive slow cookers at mass market and thrift stores. It's best if you get one with variable temperature. If you buy a used one, be sure that the liner is free of cracks and strange odors.
Another way to work with soap shreds is with a microwave oven. This method can be faster than the others, but it can also result in extremely hot melted soap, froth, and hot steam. It is best for small recipes, one pound of shreds or less.
Each microwave oven is different, so you need to experiment. Use low to medium settings. If you blast your soap on the highest setting the chances increase that it will scorch, “grow” out of the bowl, or reach an overly high temperature that will melt the molds.
If you decide to make larger batches in the microwave, be very careful of the heat. Even the sturdiest plastic can melt under the intensity of the heat. There are very few sheet molds that can stand up to the temperatures, so let it cool before risking your favorites.
Spoons, Scrapers, and Bowls
Whichever heating method you use, you will need other tools just as you have for the other soapmaking methods. As always, use only silicone; thick, heat-safe glass; and stainless steel. Although the soap will not be caustic when you get it for milling, it's still best to use nonreactive tools.
One-piece silicone scrapers with heads that are curved like a scoop are perfect. Get a couple of sizes for big and small tasks. Be sure to watch how they age — as they eventually will — because you don't want chunks of decaying scraper in the soap.
For mixing, a large stainless steel slotted spoon works perfectly. Be sure you have one that has a plastic or rubber covering on the handle rather than naked stainless steel all the way to the end.
The texture of hand-milled soap will be slightly to very uneven. If you cut it into bars, you will probably get some warping on the sides and edges as the added water evaporates. This shouldn't be seen as a flaw, but as yet another hallmark of having been made by hand.
Molds and Scoops
Make sure your plastic molds are heat-resistant. They need to be able to stand up to boiling water. Test the molds with boiling water, as discussed before. You can easily ruin a good plastic mold with too-hot hand-milled soap, especially if you're melting it using the microwave method.
Scoops are handy to make very pretty soap balls. Scrape the finished soap mass into a block mold. Then, when it's cooled but not totally hard, use a stainless steel ice cream scoop to scoop out portions. Wear latex gloves to protect your hands and always be careful of the heat.