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Making lye from wood ash?

 
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Location: Missouri
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Anybody have experience making lye from wood ash?  This lye would be for the purpose of making soap.  I've been making soap for about a year, and I'm wondering how feasible it would be to make my own lye.  I do know you need hardwood ash (for making bar soap).  I've heard of the egg test, but I wanted to hear from somebody with experience.  Also, what about saponification numbers?  Every soap recipe I have seen relies on calculating different lye concentrations depending on the saponification number of the oils used.  How can this be done if you are making your own lye?  Can you test it for concentration (beyond the egg test)?
 
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Just had a friend asking about this... would love to hear the answer
 
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I used to help my grandfather do it. It was many years ago. We took a big galvanized funnel and stuffed the bottom with course steel wool. Filled the funnel with a mixture of oak and maple ashes. My grandfather said that maple had a lot of lye but we burned more oak. We had the funnel mounted with a glass bowl under it and had a hose mounted above the funnel. The hose was left dripping, steady drip, but not running. We would adjust the water flow so that it stayed very wet, but never overflowed. The liquid that came out of the bottom was strained through old burlap sacks and then used in the soap.

I have no idea the lye content or anything like that. I do know the liquid would burn my hands if I got any on them and didn't wash it off quickly, but that was 40 years ago. I hope that helps at least some.
 
Alicia Donathan
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Gregg, thanks.  That is helpful.  This project (making lye from hardwood ash) is on my "to-do" list.  Maybe someday I'll post results here on permies.  
 
Gregg Carter
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That would be good. I have thought about doing this myself, but just not real high on the priorities list right now.
 
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I like Greg's method.  I use a slightly slanted wood trough with a small hole and wood "straw" that ends over a heavy plastic pail. I fill the trough with the ashes and set up a hose to drip water into the upper end. I have a piece of old cotton T-shirt covering the down hill hole inside.
Once you get the pail full, you have your lye, just strain it as Greg mentioned. Lye made this way is a very powerful caustic, don't get it splashed on you, it will eat clothing and skin. My last batch came out at 10 molar (Most strong acids are 12 molar, so the lye will be very strong).
 
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Bryant,

How did you test the strength of the lye you made?

I too am interested in making lye form wood ash for soap making, and as was previously mentioned all of the soap making recipes I find are very specific about the strength of the lye. It would be quite helpful to know how to test that.

Thank you
 
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Jackie Frobese wrote:Bryant,

How did you test the strength of the lye you made?

I too am interested in making lye form wood ash for soap making, and as was previously mentioned all of the soap making recipes I find are very specific about the strength of the lye. It would be quite helpful to know how to test that.

Thank you



The only way to test it is via titration, you would need a very accurate scales/liquid measure, an indicator and a acid with a known strength. It's easy enough to do when all those bits are assembled.
 
Bryant RedHawk
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Jackie Frobese wrote:Bryant,

How did you test the strength of the lye you made?

I too am interested in making lye form wood ash for soap making, and as was previously mentioned all of the soap making recipes I find are very specific about the strength of the lye. It would be quite helpful to know how to test that.

Thank you



You can use litmus paper strips or a Ph meter. As skandi mentions, back titration will be very accurate, but requires the equipment and math along with technique.

Redhawk
 
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Bryant RedHawk wrote:I like Greg's method.  I use a slightly slanted wood trough with a small hole and wood "straw" that ends over a heavy plastic pail. I fill the trough with the ashes and set up a hose to drip water into the upper end. I have a piece of old cotton T-shirt covering the down hill hole inside.
Once you get the pail full, you have your lye, just strain it as Greg mentioned. Lye made this way is a very powerful caustic, don't get it splashed on you, it will eat clothing and skin. My last batch came out at 10 molar (Most strong acids are 12 molar, so the lye will be very strong).



I don't suppose you'd happen to have any pictures of your setup? This is something I'm moving toward, myself. I've only enough purchased lye left for 1 or 2 more batches of soap, so I'd like to start working on this, soon. But, I'm at the 'very new beginner' stage. I have no idea what kind of timetable I'd be working with, how to translate from homemade liquid lye to the granulated stuff I add liquid to, etc. I've much to learn!
 
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I know this thread has some age on it. But it is a great read.
 
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Carla, you can take the leachate from wood ashes and boil off the water until it is any concentration you want, even dry.
 
Carla Burke
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Jordan Holland wrote:Carla, you can take the leachate from wood ashes and boil off the water until it is any concentration you want, even dry.


Will it crystallize on its own, or is there another step? Not that it actually matters, I suppose, since the dry lye gets weighed, anyway. I'm going to need a safe wash to boil it down, outside. Well! Looks like I'll be needing to build a rocket stove, with some extra height on the burner platform, since the though of exploding lye is a bit unsettling, lol.
 
Jordan Holland
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Carla Burke wrote:
Will it crystallize on its own, or is there another step? Not that it actually matters, I suppose, since the dry lye gets weighed, anyway. I'm going to need a safe wash to boil it down, outside. Well! Looks like I'll be needing to build a rocket stove, with some extra height on the burner platform, since the though of exploding lye is a bit unsettling, lol.



If you heat it long enough, it will dry out on it's own. It does not make very pretty crystals. It's just a blob. It is also deliquescent, so it will not stay dry unless kept airtight. I try to stir it to prevent it from forming a solid mass on the bottom of the pan as it dries out completely. I would recommend using stainless, because it is strong enough it will etch glass, and the higher temperatures would make shattered glass a more likely possibility than when just boiling water or cooking. Doing it outside is a good idea. It should not explode on its own, but definitely keep it away from things like sulfur and saltpeter. The big danger of dealing with it is if it simmers and sizzles and pops little droplets out, they will not only burn you, but eat nasty holes in you. It might not be a bad idea to keep some vinegar on hand to douse yourself if some gets on you.

I have seen the "lye from ashes" conversation pop up from time to time and have refrained from commenting (not wanting to seem argumentative, truthy, or like a know-it-all), but now may be a good time to say this: the way I understand it, wood ashes do not actually contain lye--at least in its modern parlance. If you buy lye today, you will receive potassium hydroxide. Soda lye is sodium hydroxide. The leachate from hardwood ashes will contain almost entirely potassium carbonate. Potassium carbonate is a strong base, almost as strong as potassium hydroxide, and it behaves similarly in many instances. However, it is not exactly the same, and I feel this should be remembered (such as in this case of soap making). If you are expecting nice bars of soap, you might want to experiment with a small batch first. Soap made with potassium carbonate will be gooey. As far as measuring ingredients, it is apparently problematic, as the old-timers used their sense of taste to tell if the soap was mixed right (eww!). I think you can mix quicklime (calcium hydroxide, made from burning limestone) with potassium carbonate to make potassium hydroxide (and some chalk), but I've never seen anyone do this. I just read it's what they ended up doing way back then to get KOH.

Here's a good article about "wood ash lye" soap: https://classicbells.com/soap/woodAshLye.asp#:~:text=Wood-ash%20lye%20is%20a%20solution%20of%20mostly%20potassium,which%20means%20it%20will%20be%20a%20soft%20paste.
 
Carla Burke
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I've made the mistake of working with lye without ppe and forgot to have the vinegar handy. It was not pleasant. Vinegar is now always right there and open. I also try to wear something on my arms, that I don't care about. But wearing rubber dish-washing gloves (which most people recommend) is actually more dangerous(for me), because with my arthritis, carpal tunnel, and a tendon issue in both hands, I struggle more to hang onto things, with the gloves on. I try to have the thinner nitrile gloves on, but those were really difficult to get, for a while, there.

Thank you for the information about the chemicals! I didn't know. You've given me(and no doubt, others) much to think about!
 
Alicia Donathan
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Jordan, that 's really interesting.  Thanks for the heads up re: potassium hydroxide vs. potassium carbonate.  The household lye I have been using is sodium hydroxide, however.  I'm not at all sure how the KOH works.  I had an impression KOH was used more for liquid soaps (rather than bar).  Good to know.
 
Jordan Holland
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Alicia Donathan wrote:Jordan, that 's really interesting.  Thanks for the heads up re: potassium hydroxide vs. potassium carbonate.  The household lye I have been using is sodium hydroxide, however.  I'm not at all sure how the KOH works.  I had an impression KOH was used more for liquid soaps (rather than bar).  Good to know.



Yes, that's how my recollection goes as well. NaOH makes harder soap. Ideally, drain cleaner would be KOH, to turn grease into soft soap that would wash away quicker. I think it often can be whatever is cheaper or more available for the producer to buy at the time.
 
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Jordan Holland wrote:

Carla Burke wrote:
Here's a good article about "wood ash lye" soap: https://classicbells.com/soap/woodAshLye.asp#:~:text=Wood-ash%20lye%20is%20a%20solution%20of%20mostly%20potassium,which%20means%20it%20will%20be%20a%20soft%20paste.



Thank you Jordan this WAS a helpful article and has saved me a lot of trial and error

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