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Saturday, April 17, 2010

DIY: Homemade lye soap

Before I even start, I'd like to let everyone know that this is my very first batch of lye soap. It's a VERY basic recipe using only lard and lye which is very caustic. I hope to get input on this thread and possibly some recipes from anyone else who has used this method to make soap at home. The advantage of this hot-process soapmaking is that you can use the soap as soon as it's hard enough to be cut into bars. Historically home soap makers boiled their solutions in the same way as this is done.

FIRST you need some basic SAFETY equipment. Lye is a very caustic material to work with and severe personal injury can occur!!
safety glasses or goggles or a face shield
rubber gloves
long sleeve shirt
a plastic or pvc apron
vinegar or lemon for any skin contact that might still occur

Second there are a few items you'll need for the process.
A liquid measuring cup marked in fluid ounces.
A scale that measures dry weight in ounces down to the 1/4 ounce. preferrably with a stainless steel tray. My scale measures down to .01 ounces. Your scale should have a tare function so you can measure directly into a container like a paper cup.
stainless steel, ceramic, or pyrex bowls or other heat safe containers. If there is a doubt of what your materials are made of DON'T USE THEM. No aluminum, cast-iron, tin, etc. These are reactive and will ruin your soap and container.
I used a crock pot and a hot-process recipe. I got a small one from the dollar store for less than $15. I don't remember the size, we've had it a long time, but I could have easily made a batch twice the size as what I made in it with room to spare
phenolphtheylene or litmus strips to test pH
stainless steel, plastic, or wooden stirring utensils
a dedicated candy thermometer. do not use it for any cooking after using it in the lye.
a mold of some sort. I used empty checkbook boxes lined with wax paper.

Thirdly you need the ingredients for your recipe. This recipe uses only lard and lye. I'm not interested in fragrances or aesthetics.. only getting clean. If you wish to add other oils you need to find out the saponification values of those oils. Here's a good reference calculator for other oils. Lye can be hard to get hold of as it's been used in the manufacture of drugs in recent years. I found it at Ace Hardware up town. I have invested a grand total of $6 in lard and lye so it's really inexpensive. 1lb of lard was less than $2 and the lye was less than $4.

Ok.. the science behind it:
All soap, unless it occurs naturally in a plant which contains saponins, is a result of a chemical reaction between lye and oil of some type. This produces glycerin and "salts" which is a generic term for precipitates which would normally fall to the bottom of a solution. Understand that lye and fat are opposites on the pH scale, fats being acidic and lye being alkaline. To my knowledge, all soap bought from a store contains glycerine which is a product of this chemical reaction. Look at your soap and see if it contains glycerine.

Now the math.
Lard has a saponification value of .138. That is how much lye in ounces it takes for lard (or tallow) to be 100% saponified. Because it is animal fat and all animals are not created equally, it's best to take a discount right off the top. The calculator above, if I remember correctly automatically takes 2% right off. Then you add whatever discount you want to that. I used a 5% lye discount, or fat surplus. You do this JUST IN CASE the fat is a little higher or lower than the supposed value of .138. a 2% discount will set that at .135, and another 5% makes .128 oz lye per 1 oz of lard. Follow me so far?
1 oz of lard will require .128 oz of lye for 93% saponification leaving a 7% margin of error. You'd rather have too much fat than too much lye because lye will take off much more than just the dirt. Got it? Good!
Admittedly 1 oz of soap isn't much worth the trouble or time so we have to convert all this math into something resembling a usable amount.
1 lb of lard is 16 oz.
.128 oz of lye times 16 oz of lard is 2.05 oz of lye.
--16 oz lard and 2.05 oz of lye will give us 93% saponification.
You also need a medium to dissolve the lye in. Water will be done in fluid (fluid ounces or floz.) measure and you want to use roughly twice as much water as dry weight of lye. that would give us 4.1 fluid ounces of water.. lets give ourselves some margin for error and round up to 5 floz.
The water will be evaporated off later in the hot-process cooking. so if you wanted to use a little extra, that's fine. Just keep in mind, the more you add, the more you'll have to evaporate later. I wouldn't go over 6 floz. for this small of a batch. Put the water in the fridge and get it nice and cold.

Okay.. lets get dirty..errr.. clean... err... we're gonna mess up some dishes and hopefully not get any on us.
Measure out your lye crystals into a paper cup or similar container that can be discarded.
Get your lard measured out.. the can might say 16oz, but my tub of lard easily had 18oz.. that could make a really nasty, greasy soap.. it's best to weigh out all your ingredients to make sure you get it right.
Put it in the crock pot and get it melted and then put it on the low setting.
While that's melting, go outside with a pyrex or other heat-safe container, add your 5 or 6 floz. of water to the bowl and SLOWLY AND CAREFULLY add the 2.05 oz lye crystals TO the COLD water. Using a stainless steel or plastic spoon, stir it. You want to be outside and avoid breathing in the steam that will form. The lye added to the water will immediately heat to almost boiling. I measured the temp somewhere around 185*F!
When the lye-water cools to about 110*F it's ready to go into the melted fat. CAREFULLY and SLOWLY, pour the lye-water into the pot AWAY FROM YOU. You don't want this stuff splashing up on you.. the lye is caustic and the fat is hot! Carefully stir with your plastic spoon and you will see an immediate change in the opacity and texture of the fat-lye solution.
Depending on the crock-pot, you may want to turn the setting higher. You don't want it to boil, but you do want it to be hot enough to evaporate the water. It will get noticably thicker instantly.
The hot-process cooking will force the solution to saponify by keeping it in a liquid state so that the ingredients can react freely. It will need to cook for about 3-4 hours. Leave the lid off so water can escape as needed. I went with 4 hours to be certain the reactions were done, and at the end of 4 hours the texture was consistently opaque without stirring. Dip a litmus paper in it and check the pH. It should be somewhere between 6 and 8. Some literature says between 6 and 10 but in my opinion, the more acidic it is, the more harsh. A pH of 7 is neutral, like purified water. At this point you should test the batch to see if the pH is close enough to neutral or if something went wrong. I say anywhere between 6 and 8 is great for general body cleaning.
Give it a good stir anyway and pour it into your molds. It will have to set up for a while to solidify and let any remaining water evaporate. At this point, mine is like a thick paste, reminiscent of the lard itself, but much more yellowish with a soapy feel, rather than greasy.
In a few days, I should be able to unmold it and cut into smaller bars for use in my day pack for camping trips, fish bait, fire-bow socket lube, or washing dishes or the sand out of my crack.
Clean up is simple too.. the lye-dishes can be washed in a sinkful of water like regular.. whatever small amount of residue that is left will be so dilute, that there is no chance of getting burned. The crock pot, you just wait for the residue to congeal, fill it with water, and wash it.. it's already got soap in it! DONT pour uncongealed soap down the drain.. when it cools it will clog the drain and can be a real bugger to get out!
At this point I'd like for anyone who has experience with this to point out any errors or variations in this explanation and possibly post up some simple small-batch recipes for others to try. It is dangerous working with the lye, but common sense, preparation, and careful attention will prevent accidents from happening. You should still wear your PPE because you dont want to be the example of what can happen IF something goes wrong. Carelessness and inattention can get you seriously hurt.

If you DO get some of the lye or lye-water on you, IMMEDIATELY rinse with running water for at least 1 minute, then douse the area with vinegar or lemon juice. They can also be used to clean up any spills that may occur in your kitchen.
I hope I haven't scared anyone away from making their own soap with all this talk of danger, because it really is simple and quite intuitive. I was very afraid at first, and very confused and overwhelmed by the variations in information I was getting. It seemed really complicated and dangerous and I couldn't see how folks in the "old days" could do this at home, but I'm sitting here tonight telling you that it's easy, and not nearly as scary as I thought. I have no scars or wounds, no big messes to clean up. I would not take the chances with moving around with a camera to take pictures on my first try, but I will take some as I get more comfortable with the process and edit this post to include them.
Thanks for taking the time to read this rather lengthy explanation and I hope to hear from more soapmakers in the near future!

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