How many times have you opened a package or discarded a box and wondered, "Hmmmm, this would make a great soap mold!" There is no need to throw away such good packaging and containers; recycle them. Everyday junk that we throw away make wonderful soap molds. And saying that, we have to keep safety in mind when choosing a found container. Of course you want to use safe materials and making sure that the mold itself does not react with the lye and that it survives the elevated temperatures of the soapmaking process. And eventhough that is done that it holds its shape and does not harbor any funky stuff post soapmaking.
So here are some tips on how to prepare found containers to be molds.
1. Certain metals cannot be used with lye such as aluminum, galvanized zinc, brass, bronze and tin. Sodium hydroxide (lye) combined with these metals forms hydrogen gas, which is an explosive. Lye is the principal active ingredient in oven cleaner and has the same effect on these metals as oven cleaner. Lye can be used with a glass container but only for short periods, as it corrodes the glass producing a frosted effect. If using a container such as a sardine can make sure that the can is the kind that is coated with a protective film on the inside. In addition, prepare the tin by spraying with baking nonstick spray.
2. Boxes make the easiest containers to prepare. Firstly, the box has to be sturdy. Then it has to be lined with nonporous material. Some good liners are a cut open garbage bag or some other heavy-duty plastic. Kitchen plastic film is too flimsy to use for lining the boxes. Another alternative is the thick plastic film used to protect floors for painting. If the plastic pieces won't stay put, then tape them in place. Grease paper is another liner that works well. Some folks also use butcher paper, the kind with plastic or wax on one side. Keep wax side toward contents so it will be easy to peel off once soap sets.
3. Odd shaped containers such as milk cartons, Pringles cans, pvc pipes (used) or bought new, and clay flowerpots can be prepared by spraying with nonstick baking spray - and if needed plastic liners. If the container is long such as a pvc pipe, then locate a source for plastic liners that is available in tubular rolls sold expressly for lining pvc pipes by soap supply stores. the flowerpot and cake tin is one of my favorite odd-creative expressions of soap making. The finished product can be a lavishly decorated cake or flowerpot complete with flowers.
4. Found furniture parts make excellent large soap molds. Most dresser drawers would make large and deep soap molds. Since this is a found object, estimate the approximate amount of soap the container would hold by lining with one sheet of plastic, tucking in corners. Then fill with water and empty the water in a container and weight. This final number approximates the amount of soap this container would hold, minus or plus a couple ounces. With subsequent use this number can be fine-tuned to the amount you need.
Here's my list of things that make promising soap molds:
2. Sardine cans
3. Heavy duty cardboard boxes
4. Pringles (trademarked) potato chips can
5. Plastic drawer liners
6. Plastic Tupperwaret (trademarked)
7. Milk cartons
8. Clay flowerpots
9. Pvc pipes available at hardware stores, sold by the foot or yard. Most places usually have end caps too.
10. Plastic shoe boxes
11. Organizer containers
12. Dresser drawers
13. Gift boxes
14. Cake tins (then slice into cake slice soap!)
15. Chocolate boxes (yumm. Save some of the chocolate and make soap and give it back to the giver!)
16. Deli salad containers, especiaally the wonderful stury boxes and plastic holders found in gourmet type stores