I will soon be posting a soap-making tutorial. At least one of my would-be soap maker friends has expressed reservations about working with lye. In preparation for the tutorial, I’m posting this list of thoughts about safely using lye for soap-making:
Wear long sleeves, rubber gloves and safety goggles. Things splatter when making soap. On skin, those splatters could leave burns. In eyes, they could be even more dangerous.
Use non-interactive containers. Lye can interact dangerously with aluminum, magnesium, galvanized zinc, tin, chromium, brass or bronze. Don’t use containers or utensils made of these. I use plastic containers and plastic, wooden or stainless steel utensils.
Glass may also be dangerous. I recently read that over time the lye may cause the glass/pyrex to shatter. Use stainless steel or heavy duty plastic instead.
Dry lye granules aren’t going to burn a hole in you or your countertop. If some dry granules touch your skin, you might not even notice right away. They will become progressively more irritating/painful/dangerous as they interact with the moisture on your skin. Don’t get them in your eyes or on the floor where pets or babies might encounter them. If they spill, wipe or sweep them up, throw them away or rinse them down the sink.
Lye gets hotter and more dangerous when it encounters liquid. A container of lye-liquid is a different and more dangerous animal than a few dry granules of lye.
Chemical interactions involving lye generate heat. There are two points in the soap-making process where you initiate a chemical reaction. The first is when you add the lye into the liquid. The second is when you add the cooled lye-liquid into the oils. The chemical interactions that are initiated at these points can generate a lot of heat even if no outside heat is being applied. Much attention in soap-making is devoted to counteracting those high temperatures, such as by cooling the liquid before adding the lye, setting the container in an ice-water bath, removing heat from the melted oils before adding the lye-liquid, etc.
A particularly dangerous phase of working with the lye is the time between when you add the lye to the liquid and when you pour the lye-liquid into your oils. Before that point, the lye is dry granules that can be brushed off or swept up without too much trauma. After that point the lye-liquid is poured into the oils, becomes diluted, and the neutralization process begins. Between those two points, however, you have an extremely hot, extremely caustic mixture of lye-liquid. It could cause serious burns, probably third degree, and permanent damage to eyes.
Warn family members about what you’re doing and keep children and pets out of the room.
When the lye and liquid meet, they are going to get hot. Depending on the type of liquid and other factors, perhaps really hot, even to the point of boiling over or creating a little mini-volcano. You need to take steps to prevent this from happening and have a plan of action in place to respond if it does.
Prepare a bath of ice-water in the sink or a plastic tub. This is both to deal with a mini-volcano if one occurs and to cool your ingredients.
Lye is a base. It can be neutralized with an acid. I use a jug of cheap, Costco white vinegar. Pour some into the ice-water and keep the jug nearby for any emergencies. Now the ice-water serves a triple purpose. 1) It is a bath for cooling hot containers of lye-liquid, melted oils or cooking soap. 2) It is as an emergency neutralizing bath to submerge a caustic emergency. 3) It is a place to put used utensils and containers that have touched lye.
Get the container of liquid for the recipe very cold before sprinkling the lye into it. I put mine into the freezer and get it right on the brink of freezing (but not quite to the point of freezing because mixing lye into frozen liquid is a pain).
When the lye and liquid meet, they are going to emit fumes. At a minimum, these fumes will be unpleasant; they might cause irritation in sensitive people. To avoid fumes in the house, set the container of very cold liquid into a tub of ice water, take the whole thing outside, and sprinkle the lye into the liquid out there. (Make separate trips so you can use two hands to carry the lye.) If you have snow, you wouldn’t need the tub of ice water; just set the container of liquid into a snow bank. At a minimum, open windows to air out the fumes.
NEVER POUR LIQUID INTO LYE. YOU WILL CREATE A VOLCANO. Sprinkle the lye into the liquid (slowly and carefully)—not the other way around.
Avoid breathing the fumes while stirring the lye until it is fully dissolved in the water.
Let the mixture cool off in the ice-water bath or a snow bank before adding it to the oils. I cool it until the outside of the container feels cool or cold to the touch.
Cool the oils too. Once the hard oils/butters have melted, turn off the heat and add the liquid oils. The addition of those room temperature liquid oils will cool the mixture. Sometimes I take the crock out of the base and set it in the ice water along with the lye-liquid container and let them both cool (making sure the oil mixture does not get so cool that it starts to seize/harden).
Pour lye-liquid gently into the oils. All of this cooling is intended to counteract the heat that will naturally be generated by the chemical interaction that begins when the lye is added to the oils. Be sure to wear long sleeves, rubber gloves and safety goggles. To avoid splatters, pour the lye-liquid gently into the oils.
Use a pot that is comfortably big for your batch size. The cooking soap can “boil over.” Even if it doesn’t reach that point, it will naturally expand and creep up the sides of the pot. Use one that comfortably accommodates the size of the recipe with room to grow.
Neutralize as you go. As soon as I am done with each container that has touched lye, I set it into the bath of ice-water and vinegar. When I have a break in making the recipe, I slosh them around in that water (wearing rubber gloves), wash them off and put them on a towel to dry.
Don’t rely solely on this post. There is an abundance of soap-making information available on the Internet. Each source will remember something the others missed or explain something in a slightly better way.
Good luck, be safe and have fun!