Does Soap Expire?
Walk down any aisle in a beauty store or the cosmetics and bath section in a super market. Almost every product you see will have an expiry date. Often it will either say “best before” or “use within __ months/years after opening.” Given that commercial soaps all seem to expire, many people who make their own soap at home or who are starting homemade soap business ask the question: does soap expire? Followed by: when will my soap expire?
The question on when soap expires has always been tricky. First, it is important to understand that commercial soaps are made in large batches, and therefore are not given the same care and attention that homemade soap is given. Second, because the batches are so large, and because it is for large scale retail, companies often have to use certain chemicals to make their product stretch longer. Because of this, in the case of soaps, the question of “does soap expire” is answered with a very simple yes.
Commercial soaps can expire because age can alter the chemical composition of the soap. Many often argue that manufacturers do not list the real expiration date so that consumers are encouraged to buy new soap instead of sticking with a bar bought several months before. The truth is, however, manufacturers print earlier expiration dates for safety reasons. They don't want to risk people using their product when it is no longer safe. So they will usually give a date six months or more prior to the actual expiration of the product.
When it comes to handmade soaps, the story is different. You will answer the question “does soap expire” with “It depends.” What does it depend on? Several things. First, it will depend on the lye measurements. You have to make sure you measure your lye exactly because having more or less of the chemical can dictate how long your soap will last as well as how good the soap will be. Soap with no lye discount will keep for a very very long time. It might lose its smell, but it will still be good.
Second, how long handmade soap will last depends on how much fat you put into it. When you add fat to soap, you lessen its longevity. However, most of us will need to add fat to the soap. The best way to make soap that will last a long time is to make sure the fats are very well blended. Also, the un-saponifiable ingredients you put into a soap can affect its expiration. Adding organic herbs, flowers, bits of fruit, etc, can shorten your soap's shelf life simply because these things do not last long.
As a rule of thumb, handmade soap that is well made should last about 24 months before it is potentially irritating to the skin. Be sure that you cured your soap completely, and once the curing process is complete, store in a cool dry place that has some ventilation. Storing in an airtight container will not be good for the soap because it can sweat. Finally, when asking yourself “does soap expire,” consider what the soap looks like. Does it look moldy? Smell bad? If it doesn't look or smell right, you are better off not using it!