ElizabethGreene - 6-7-2022 at 08:08
I need to process a lot of wood ash to concentrate potash, a mix of Sodium and Potassium salts including Hydroxides over a campfire.
I know I can't use anodized aluminum for cooking this. :/
Is it okay to do this in a large cast iron kettle?
I know these containers and solution were historically used to make Lye soap, but I wanted to ask before I try it.
Thanks!
Texium - 6-7-2022 at 08:11
Should be fine. Iron oxides aren’t amphoteric, and the metal shouldn’t react either. If the cast iron is seasoned though, the highly basic
solution will destroy the seasoning and the iron will likely rust heavily afterwards.
Thanks
ElizabethGreene - 7-7-2022 at 18:32
Thanks! I'll reserve some materials to reseason the iron afterwards.
Fulmen - 8-7-2022 at 00:17
It's perfectly safe, I've been using a cast iron pot for hot, caustic solutions for years with no damage. But as Texium mentioned it might rust
afterwards unless seasoned.
RogueRose - 8-7-2022 at 08:36
IDK if you are heating the ash/water mix and allowing it to boil or what you are doing but that isn't really necessary to extract the lye. I've
processed large amounts (20-30 gallons of ash) many times and I would add tap water and I could extract as much as the water would dissolve. The
hardest thing was trying to limit the amount of water I had to boil off after 2-4 washes after the first extraction b/c the ash retains so much water.
I usually use a plastic container for dissolving the lye and I've even used ziploc bags which work very well if you hang them with one corner pointing
down & cut a very small hole to allow the solution to drain out. once it drains, pinch the corner, open the top, add some more water & allow
it to filter down through. I would avoid mixing the ash/water at this point & keep the ash as it settled & allow gravity & water to do
their thing to finish the wash/rinse extraction.
When I did my extractions I would remove any material that didn't pass through a window screen before adding water. This takes care of most of the
charcoal & you are left with fine ash. I usually end up getting about 8-11% "lye" by weight once I evaporate the solution. The yield will vary
greatly depending upon the type of wood you were burning. Hardwoods are by far the best!
Are you making soap with this? I've made a ton of soap over the years but I've never tried it with the lye I extract for some reason (potassium based
soap is so much softer/mushy if not a liquid..) LMK if you have any questions & I'd like to see your results if making it from wood ash lye!