Using stearic acid or stearin in candlemaking
You can broaden your candle-making repertoire by exploring the uses of this handy additive.
Photo Credit: Stephanie Phillips
Stearic acid, also known as stearin, is a long-chain fatty acid often used in candle-making. Its primary property is to raise the melting point of the wax mixture, making the resulting candle harder and more durable.
The derivation of stearin from rendered animal fat aided the industry's transition from tallow to paraffin. Paraffin became popular because it cost less to produce and burned cleaner than tallow. However, its lower melting point--between 120 and 140 degrees Fahrenheit--caused problems. The hardening effect of stearin, with its melting point of up to 160 degrees Fahrenheit, made paraffin a much more viable option. Today, most commercially produced candles are made from a stearin/paraffin mixture.
You can usually find stearin powder at the same craft stores that sell paraffin and beeswax. It can be made from vegetable oil as well as from tallow, so if you prefer to avoid animal by-products you can still take advantage of this useful additive. The typical proportion is 10% stearin to 90% wax by volume. A candle made from this mixture will drip less, sag less, and burn longer. As the ratio of stearin to wax rises, these effects will increase. You can even use 100% stearin for an entirely dripless, smokeless, and very long-lived candle.
Stearin simplifies the production of molded candles. A mixture of stearin and paraffin will shrink as it cools, allowing your creations to easily pop free of their molds. However, because stearin can eat away at rubber and latex, it's best to avoid using it with molds made of those materials.
A variety of visual effects can be acquired with stearin. A lower ratio can result in an attractive, but not always desired, snowflake effect. In higher proportions, stearin makes wax more opaque and colors brighter. You'll want to experiment to find the best balance for your project. To increase the glossy finish of a stearin-paraffin taper, dunk the candle in cool water immediately after you've finished dipping it. The resulting lacquered look comes from stearin's crystalline structure.
One technique in which stearin is very useful is overdipping. This process involves finishing off a normal candle by dipping it in a separate high melting point wax, such as a mixture of 30% stearin to 70% paraffin. This forms a hard outer shell which will be more resistant to melting. As the candle burns, the outer shell remains, containing the softer molten wax inside. Not only does this technique reduce mess, it extends the life of the candle; since less wax drips away, more of it will be consumed.
Overdipping provides a handy shortcut for coloring a candle. Instead of coloring all of the wax, you can simply overdip an uncolored taper in a colored mixture whose melting point has been raised by a high stearin content. However, because of the opacity caused by high stearin content, you'll want to leave it out of your overdipping mixture when working with dried herbs and flowers. Use instead another high melting point wax so that you can see the botanicals through the overdipped shell.