How do I make soap?
May 16, 2009 9:32 PM   Subscribe

I want to start making homemade cold-process bar soap in my kitchen. Help?

I've seen several basic instructions online, but if anyone has any specific (vegetable-based) recipes they'd like to send my way, I'd appreciate it. I have assorted essential oils that I can use, and would like to experiment with using goat milk at some point.

Also, where can I get lye in/near Brooklyn, NY? How much ventilation is required for a "well ventilated room" for mixing lye safely? My kitchen has one average-sized window and a fan that I can point toward it- should that be safe, or should I do it outside?

Anything else I should know? Thanks!
posted by cheerwine to Home & Garden (17 answers total) 12 users marked this as a favorite
You can get lye at the grocery store. Crystal Drano (and other crystal drain cleaners) is/are lye. (I think they still sell it at grocery stores.)

Looks like Ace Hardware sells it, even if the grocery store does not. That page notwithstanding, I'm sure they sell them in singles.
posted by Chocolate Pickle at 9:39 PM on May 16, 2009

When it comes to caustics, I would err on the side of too much ventilation. And if you don't wear glasses, I would suggest safety goggles. Lye can blind you just as fast as hydrochloric acid.
posted by Chocolate Pickle at 9:41 PM on May 16, 2009

I learned how to make both cold and hot process soaps by watching YouTube videos. There are a ton of really informative ones out there.
posted by iconomy at 10:22 PM on May 16, 2009

I've never done this so I'm just guessing. But wouldn't it be a good idea to keep several bottles of white vinegar around in case lye gets spilled on you, or something you care about? (Lye scares the hell out of me, so maybe I'm being paranoid here.)
posted by Chocolate Pickle at 11:06 PM on May 16, 2009

Redgum Soaps has instructions and a few basic recipes.
posted by harriet vane at 11:16 PM on May 16, 2009

Do not use aluminium pans as lye corrodes them.
posted by indienial at 11:21 PM on May 16, 2009

If you have any young kids, make sure the lye is kept locked up away from them, and discard any mixed lye immediately; it is milky white when mixed in water, and it is all too common for a child to see a container of lye sitting around and drink it, leading to serious esophageal injury. The point about the safety glasses is well taken; lye is actually worse than hydrochloric acid when it comes to causing injury. I am not telling you not to use lye; just have a healthy respect for it.
posted by TedW at 4:04 AM on May 17, 2009

Best answer: I've made lye soap in the kitchen before and always tried to have a window open for the mixing part. The fumes can be very potent. Also - the lye mixture gets pretty hot for a few minutes, so the gloves are a good call for that reason as well. I've used plain Red Devil lye which is (was?) available in the local grocery store alongside the Liquid Plumr and related items. Like others have mentioned, a hardware store should have it. The recipe I used was from an article online that I can't seem to put my hands on ATM, but it was ideally suited for small-batches and experimentation. The fats, as I recall, were lard and maybe olive oil.

Hardest parts? Watching for the trace (really not a big deal) and then waiting for the stuff to cure so we could use it. Locating essential oils for fragrance was not great either, but that was because my local selection wasn't all that great. Mail order is the way to go, but I bought a couple of small vials at an herb shop down the road because I was impatient.

It was great for shaving, by the way. Lots of glycerine! Soapmaking is fun and now I want to do some more. Good luck!
posted by jquinby at 5:15 AM on May 17, 2009

MMS is a company that sells soap-making supplies. They have a lot of information and recipes on their website, but for me, the most useful is the lye calculator. It lets you input the type of oil/fat you're using and other ingredients to calculate the correct amount of lye. As far as lye goes, you don't need a lot, and I found Red Devil at Safeway, so I imagine that you won't have any trouble finding it at the grocery store.
Just a little tip that my mom taught me- Pringles cans are perfect soap molds. After you pour, and it's cured for a while, but still soft enough to cut, you just peel the can off the soap and slice. You'll have these nice-sized tablets of soap. And you have an excuse to buy chips too!

Have fun!
posted by dogmom at 6:23 AM on May 17, 2009 [2 favorites]

Be careful with trying to substitute drain cleaners for straight lye. Often, drain cleaners have chunks of aluminum mixed into is so that it will heat up quickly. (That's part of the drain cleaner magic- not only does it "eat" the clog, it also heats it up and liquifies it. Since many clogs are grease based.)

Yes, lye is dangerous. It happens to eat exactly the same stuff we are made of. But it's not the worst thing in the world, either. The fumes are far more dangerous than the lye itself. (Mostly because of the droplets/vapor getting into your lungs where it can't easily be rinsed...) Wear safety glasses and gloves and work carefully, and remember the rule to always add the acid/base to water, never add water to the acid/base. If you get some on your skin, you won't notice it right away, but will start to feel a pinching/burning. Run the affected area under cold water. If you gently rub the affected area, it will feel slippery. When it stops feeling slippery, you are usually good to go. Always wash up afterwards regardless.

Better to use baking soda to neutralize spills than vinegar. You don't want the acid in the vinegar further irritating a burn. And it's exothermic, causeing a heat burn as well.
posted by gjc at 8:37 AM on May 17, 2009

Baking soda is an alkali, just as lye is. How can baking soda neutralize lye?
posted by Chocolate Pickle at 8:55 AM on May 17, 2009

Best answer: For anyone making homemade soap: never use Drano! It has additives and chemicals that will mess it up. You can only use 100% pure lye (sodium hydroxide). Looks like Red Devil is gone off the shelves, use one of the certified suppliers from the soap and candle link above.

Another book by Susan Miller Cavitch, The Natural Soap Book, is worth picking up for the veggie recipes. However, she recommends an 8% lye reduction and I would go with 6%, using the MMS lye calculator, so you won't get spoiled/rancid soap. Don't use grapefruit seed extract either. You probably will want to cut the 12 lb. recipe in half.

The best thing to do is make sure you have all your supplies and tools prepped. Get your mold ready first, hopefully in a place where it can sit undisturbed for 24 hours.

Lay some newspaper on your counter, then put your scale on top of that. Put your distilled water in the pot you'll be using for lye, an enamel or stainless steel pot. Place that in one half of a double sink and fill the sink with cold water and throw in some ice cubes - this will cut down the cooling time. Then measure your lye crystals into a dry container set on your scale. I found the tall round plastic deli containers, washed and dried thoroughly, pretty handy. Wearing gloves and goggles, measure the lye using a plastic or stainless steel scoop into the plastic container. Then pour it slowly into the water, keeping your head back. Stir enough to dissolve, then walk away. Yes, you'll want the window open and the fan blowing out, but after the initial dissolving, it will be okay as long as you don't stick your face right above the pot and suck in fumes.

If you're using a combo of liquid and solid oils, weigh and pour your liquids (i.e., olive oil) into a second pot, such as a 12 quart enamel, and set it into the other side of the sink. Then weigh your solid oils, one at a time, melt, and stir them into the liquid oil. Take the temp of the lye and then the oils. I used 120 F for both as a mixing temp. If the oils get too cool, you can run hot water into the sink around the pot to keep them warmer, but if you use an ice bath around the lye water, it should cool down fast enough. When they're both around 120 F, carefully pour the lye mixture into the oils and stir. If you're stirring by hand, it can take a while, up to 2 hours, so it helps to have a companion. Otherwise, you can use a stick blender (immersion blender), which will cut the time way down. Never pull the stick blender out while it's running.

As it gets close to being done, it will turn lighter and lighter. The consistency will be like liquid pudding. Then pour the mixture into your mold, cover it with say, a piece of cardboard and some old towels or a blanket, and let it sit for a day. Clean up your supplies right away, using lots of dish soap. I used to rinse the lye pot right away, then fill it with soapy water and my lye spatula and scoop. After pouring the soap into the mold, you can rinse your soap pot, then fill it with hot soapy water and your soap spatula.

One great simple soap is spearmint. Make a very strong spearmint tea using double or three times what you'd use for drinking, with your required amount of distilled water. Strain and chill in the fridge until you're ready to mix in the lye. Then when the soap is thick, at the end, pour in 1 to 2 oz. of spearmint essential oil. If you use loose dried spearmint, you can stir in a small amount of the leaves, squeezed of water, for visual effect. Everyone loves this soap, men and women, and it's not as harsh as peppermint.

Make sure you cure your soap bars in a cool, dry place, I used shelves in a dry basement lined with paper bags (newsprint will come off on your soap so don't use that).

If you're nervous about the process, you may want to find a class or soap makers' group in your area. And yes, having a jug of vinegar nearby in case of lye spills is good advice, but the best advice is to treat the lye with respect in the first place. Allow yourself plenty of time and of course, keep it away from kids and pets. The last thing you want to do is get jostled when measuring and clean up lye crystals.

Once you've done it a couple of times, you can play around with more recipes and additives. It's great fun and makes lovely presents! Good luck!
posted by Marie Mon Dieu at 9:03 AM on May 17, 2009 [3 favorites]

Baking soda is an alkali, just as lye is. How can baking soda neutralize lye?

Bicarbonate is weakly basic and is a very good buffering agent.
posted by TedW at 9:35 AM on May 17, 2009

Buffering lye is the last thing you'd want to do. What you want is to neutralize it, and for that you need an acid.
posted by Chocolate Pickle at 10:01 AM on May 17, 2009

Regarding lye spills: your best bet is to ask the supplier their specific advice.
posted by Marie Mon Dieu at 10:07 AM on May 17, 2009

Mixing lye with acid can cause a reaction that produces heat. Use water to dilute lye spills. First aid measures for lye are on the MSDS.
posted by oneirodynia at 2:50 PM on May 17, 2009 [1 favorite]

Buffering lye is the last thing you'd want to do. What you want is to neutralize it, and for that you need an acid.

Why would buffering be undesirable? As mentioned above, neutralizing a strong base with a strong acid can be highly exothermic, causing further injury. Also, NaHCO3 dissolved in water produces among other things carbonic acid so that gives you a proton donor AKA an acid.
posted by TedW at 7:23 PM on May 17, 2009

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