I have never noticed any rancid taste....and I can detect rancid a mile away....don't know why not....but guess the oil gets "cured".....like a dry cured ham.
Wine is fine to deglaze....just don't simmer anything in wine for a long period.
Linda C

I used to use one fry pan and one dutch oven a lot. Never picked up a rancid taste. I will admit I did not use it for Tomato sauce.

Thanks! What I needed to know.

I think part of the key to keeping seasoned cast iron happy is using it really really regularly. We have a pan that's used for breakfast meat every morning, and it's soooooooo sweetly seasoned. As good as a commercial non-stick, and no flavor transfer at all when it gets used for other things.

But, I also suspect that whatever the "seasoning" is is partially destroyed and reformed every time that it's used---so no single bit of the black ook is really staying in place for very long.

Any chemists out there?

I believe what happens is that a carbon layer builds up on the cast iron. Other cooking pots are too smooth, whereas cast iron has a rough enough suface for the carbon to grab onto.

The ultimate non-stick pan would have a diamond coating, so carbon is part-way there!

By the way, I use a little soap in mine everytime I wash mine, and it worls just fine. I do NOT soak it, however.

What if I don't use the pan regularly?

I bought a cornstick pan this week and don't anticipate using it more than once a month at most. I would like to coat it with hot bacon grease before each batch but seems like I've read somewhere that it would taste old/rancid if I did that.

I have a dutch oven and skillet that I never use for the same reasons.

I have several pieces of cast iron cookware and I don't use any of them more than once every couple months. It's not that I don't like them because I do but I have other cookware that I think is probably a little better for most of the kind of cooking I do. I simply apply a light coat of vegetable oil (I use canola) to the cast iron before I put it away. When I'm ready to use it again I put in a teaspoon or so of oil and wipe it out thoroughly with a paper towel. This will remove any residue left from the previous coating. I like to use a little bacon grease for searing meat so I preheat the cast iron then wipe a little bacon grease in the pan and I'm good to go.

"I'm assuming this is from a build up of oil in the pan and never washing the pan with soap."

Not really - what happens is that oil penetrates the microscopic pores in the cast iron during the seasoning process and gets baked in (chemically it makes a polymer of the oil on the surface of the pan). This keeps the food particles out of the pores, hence the non-stick tendencies. All you have to do to maintain that layer of polymerized stuff is wipe the pan with oil after use. Cleaning with soapy water doesn't affect my pans, because I wipe them with oil and dry them on a warm burner before storing them. That rebuilds the polymer layer a bit.

"I bought a cornstick pan this week and don't anticipate using it more than once a month at most. I would like to coat it with hot bacon grease before each batch but seems like I've read somewhere that it would taste old/rancid if I did that."
Season it with a vegetable oilbefore you use it, use the bacon grease, scrub it with soapy water after the muffins, wipe it dry and oil it lightly with any vegetable oil (except soybean oil, which oxidizes into a fishy taste).

Same with the skillets and dutch oven: soapy water to remove the food residue, then a wiping with fresh oil and dry it on a warm burner.

If your skillet or whatever gets burnt or any stuck on food, do not use hot or soapy water and scrub it off. Instead pour oil in followed by a couple of tablespoons full of salt, and scrub with a paper towel until clean then wipe out.

If your pan looses its seasoning or cannot be cleaned with oil and salt, place it in the oven and run through the cleaning cycle. When done re-season.

I regularly scrub mine with hot soapy water, even boiling soapy water in them, then reoil them, and they retain their non-stick properties. That's the way my granny taught me.

I thinnk there is a good bit of folklore about the care and feeding of the things. About all that is 100% true is that they rust like heck if you leave them to sooak, and they do not like being run through dishwashers.