As someone relatively new to cast iron (around a year of cooking with it), I am inclined to believe the parts of this article that I cannot validate through my own experience, because the other parts match what I have learned through experimentation. However, I must point out that a year ago, I would have no way to recognize this. Whether or not this article is correct, it is at the same level of heresay as every other article, reddit comment, or youtube video out there (like the carbon steel video linked in the replies, which says never to use soap).
Despite the flax oil article being bad science, it is still the most science of any of the cast iron information out there, which is why it continues to enjoy such popularity. Even if it is bad science, it at least provides some hypotheses to test!
Here's my hypotheses on soap (edit: rephrased to better reflect my meaning):
1) Soap is fine to use; it will not damage the seasoning.
2) Seasoning is often damaged (at least a little) while cooking and it is important to re-season regularly to keep the pan in good shape.
3) If you do not use soap, the amount of oil left on the surface is similar to the amount you would want to wipe on when re-seasoning.
Basically, I think no soap + dry on stove is a shortcut to avoid the process/effort of reseasoning the pan (especially if you do the oil-and-salt-as-an-abrasive trick). Perhaps you'll get better results using soap and then wiping on oil, but it's more work and many people don't do the second part. Thus, they see better results when they don't use soap.
This would explain why some people tell you you need to reseason after every use, while others say that's bubkis, and why the same is true of soap avoidance.
To test: try all 4 combinations of soap/no-soap and reseasoning/just-drying (always dry the same way, on the stovetop).
As a data point, I use a little soap when it feels needed (every few times, usually) and add seasoning when it feels needed (less often). Seasoning remains great (fry eggs without sticking).
These are my most often used pans, and have remained that way for many years.
Fwiw I rarely need or use a scraper or salt while cleaning , I’ll “deglaze” if there is fond in the pan, even in the rare case that I’m not using the result for anything.
As of writing the GP comment, I am starting to informally test the hypothesis as well. I've switched to sponge + soap to fully clean the inside with every use (after chain mail to remove larger bits, if needed), then dry on the stove & re-oil.
Specifically the idea is that IF the seasoning layer is quite durable and is difficult to damage or wear through, except by the rough metal of the spatula I use, then the best seasoning should be achieved by thoroughly cleaning any contaminants off it and then applying a fresh coat of oil.
It will likely take longer than the HN comment window before I feel comfortable drawing any conclusions, so I'm not sure how I'll follow up on this. Perhaps I'll post something at https://smichel.me/castiron (currently this page does not exist).
You asked if I could look at this in a different part of this comment thread.
What you say seems more or less correct to me. I think if you approach cast iron that way, you will have good results.
Basically, you don't want the pan to look "not-oiled", and how much effort you need to put into that depends on how much you are removing the existing oil during the cooking process.
I think the "looks oily" test is the proper determinant for if the cast iron is in good shape. Trying to develop a "seasoning" layer is likely to just cause frustration.
Hm, you're right, thanks for pointing this out. There was no contraction in what I meant, but I didn't express what I meant correctly.
They don't conflict if the seasoning is already damaged (during cooking) before cleaning it. Cleaning with soap would not repair it at all (thus, reseasoning is required), whereas if you don't use soap, the pan is reseasoned in the same step as drying it on the stove.
Part of the problem was that I was overloading the word "reseasoning" to also refer to doing it in an explicit step (ie, the wiping on/off of oil) as well as the effect of rebuilding the layer of seasoning.
Despite the flax oil article being bad science, it is still the most science of any of the cast iron information out there, which is why it continues to enjoy such popularity. Even if it is bad science, it at least provides some hypotheses to test!
Here's my hypotheses on soap (edit: rephrased to better reflect my meaning):
1) Soap is fine to use; it will not damage the seasoning.
2) Seasoning is often damaged (at least a little) while cooking and it is important to re-season regularly to keep the pan in good shape.
3) If you do not use soap, the amount of oil left on the surface is similar to the amount you would want to wipe on when re-seasoning.
Basically, I think no soap + dry on stove is a shortcut to avoid the process/effort of reseasoning the pan (especially if you do the oil-and-salt-as-an-abrasive trick). Perhaps you'll get better results using soap and then wiping on oil, but it's more work and many people don't do the second part. Thus, they see better results when they don't use soap.
This would explain why some people tell you you need to reseason after every use, while others say that's bubkis, and why the same is true of soap avoidance.
To test: try all 4 combinations of soap/no-soap and reseasoning/just-drying (always dry the same way, on the stovetop).