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Re:Chemistry of Cast-Iron Seasoning (2010) by chipsa on Sunday January 10, 2021 @02:09PM (#25718339)
Do not use homemade soap. Homemade soap is made with lye, which is the entire reason why people said not to use soap, once upon a time. An unreacted lye will start to strip seasoning.

Use dish detergent (commercial dish soap). It's made in a different way, so you can't get un-reacted lye.

Re:Chemistry of Cast-Iron Seasoning (2010) by DanBC on Sunday January 10, 2021 @02:47PM (#25718835)
If you have unreacted lye in your soap you're going to have more problems than just stripping the seasoning off your pan.
Re:Chemistry of Cast-Iron Seasoning (2010) by chipsa on Sunday January 10, 2021 @03:06PM (#25719056)
I mean, if you have a bunch, yeah, you're going to have more issue than just stripping seasoning off. But most of the problem is just the slightest hint excess from making sure the entire volume of oil is saponified.

It's part of why you had the rubber dishwashing gloves get invented: soap used to be harsher, and one of the reasons why is the fact that soaps were made with lye.

Re:Chemistry of Cast-Iron Seasoning (2010) by OJFord on Sunday January 10, 2021 @07:27PM (#25722290)
Homemade X is made with whatever you made it with...
Re:Chemistry of Cast-Iron Seasoning (2010) by chipsa on Monday January 11, 2021 @04:12PM (#25737081)
Homemade soap is soap. The only way to make soap is the saponification process. Which involves lye. The oil used can vary, but a strong alkali is required, and any strong alkali you use is going to do the saponification process on your seasoning.

Commercial dish soap can be soap, or it could be detergent. Detergent is made differently, and doesn't necessarily involve lye.

Re:Chemistry of Cast-Iron Seasoning (2010) by OJFord on Tuesday January 12, 2021 @03:49AM (#25744054)
From Wikipedia:

> The production of toilet soaps usually entails saponification of triglycerides, which are vegetable or animal oils and fats. An alkaline solution (often lye or sodium hydroxide) induces saponification [...]

i.e. that's the usual process, and it often involves lye. (It elsewhere mentions potassium hydroxide too.)

Anyway my point really wasn't too disagree about how to make soap, I've never done it, it just seemed weird to me to tell someone how they made something and that it's a problem, vs. 'Did you use lye? If so...' or even 'Assuming you used lye, ...'

For example, I think what you call 'commercial dish soap' I would call 'washing up liquid' (never soap, not would it cross my mind if someone else said 'soap') so a slightly different conversation could easily have been based on a wrong assumption about what the created thing was or was used for.