School me on cast iron!

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Okanagan:
Flash rust on sanded cast iron.

For those who have sanded cast iron skillets or Dutch ovens smooth, how do you handle the flash rust when you clean the sanded dust and particles from the finished surface? I washed my first one in cold water and soap before oiling and seasoning. When water touched the bare clean cast iron, rust flashed across it within a fraction of a second. With warm water it is even quicker. I rubbed off the rust as quickly as possible with an oily rag but didn't like having it rust at all.

I now sand with a minimal coat of grape oil and wipe/flush the finished surface with several washes of clean oil. That way the clean bare cast iron surface never is exposed to air or water and so does not flash rust. I’m not convinced that an oil wash gets all of the grit particles out of the cast iron pores, but I haven't noticed any.

Anyone got a better method of sanding smooth and cleaning while avoiding nearly instant rust when the bare metal loses its seasoning coat and is exposed to oxygen?

Just to be clear, sanding cast iron smooth is a one time process for each utensil, not some repeated cleaning event.

Bullkllr:

--- Quote from: Okanagan on February 24, 2026, 11:23:04 AM ---Flash rust on sanded cast iron.

Anyone got a better method of sanding smooth and cleaning while avoiding nearly instant rust when the bare metal loses its seasoning coat and is exposed to oxygen?

--- End quote ---

There are some cast iron gurus who recommend 'chemical etching' before that first seasoning. Basically a vinegar solution boil/simmer. The goal is to force a black/oxide coating onto the piece to allow better and faster seasoning. You wouldn't have to worry about further flash rust as you are literally forcing an oxide coating onto the iron.

I'm no expert, so I recommend doing your own research.

I tried it once recently on an heirloom pan I was struggling to season. It seemed like the pan was so smooth seasoning was not adhering :dunno: . So I took it down to bare metal and tried the chemical etch with vinegar. I can't say the results were as dramatic as I hoped, but the pan did seem to pick up seasoning better than before.

jamesfromseattle:
I just came on to this thread to admit that I'm mean to my cast iron. I regularly scrape stuff off with a metal spatula. I use soap when it's really dirty. I cook tomato sauce. I've cooked on top of charcoal and over an open fire, and I regularly use it on an induction stove. The bottom of my favorite pan looks like a scene from ghostbusters, but the cooking surface looks great and I fry eggs every morning without issue.

The only things you absolutely can't do are dunk it in water when it's hot or add too much liquid once it's ripping hot. I learned that the hard way when I first tried cast iron, but I've used the same cheap lodge pans for 15+ years and I assume they'll last forever.

I appreciate that some folks keep their antiques looking beautiful, but I love cast iron because I can beat it up.

slavenoid:
Flash rust happens on bare iron regardless of sanding. Washing in cold water helps. Drying it as quick as possible is important. I swing the pan around using the air movement to help dry then oil instantly while still cold. Compressed air would probably look less silly than what I do.

CP:
The $22 Lodge works just fine. My only complaint is that the stubby handle is awkward and it gets hot.

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