Machine Smoothed Versus Power Sanded

R

RobHerrington

Member
From the primer on this site:

With cooking surfaces machined smooth after casting, and subsequently "seasoned" by the build-up of polymerized fat from cooking, vintage cast iron is considered the original "non-stick" cookware.

How is "machine smoothed" any different from sanding a rough surface, which is discouraged?
 
Because it was done with a spinning grinding stone on a rotating pan, and represents the original factory finish. Anything which changes either the as-cast or factory finished patina is considered detrimental to collectible value.
 
Thank you sir. What if it's not collectible? I only have two that are crying out for power sanding. They are Made in USA but otherwise unremarkable. I can't guarantee that they will be smoother after sanding, but they can't be any rougher.
 
If a rough, unpolished modern Lodge is all you have and wish to approximate the surface of a vintage factory polish ground pan, by all means go ahead. Seems like a lot of unnecessary effort, though, if you already have or can obtain pans that are already factory polished. My 1950s #10 Lodge skillet cost me $10. Even twice that won't buy a new unpolished #10.
 
I think I understand. I do have several that are already polished, but the ones that are not seem utterly useless, and it bugs me having them sit uselessly on the shelf.

If I had it to do over again, I wouldn't have bought them in the first place. But since I did, I think they should at least be made usable before I give them away.

When we're talking, what application would most closely approximate the factory polishing they never received?

I appreciate your advice! Thanks again.
 
There are multiple youtube videos on the subject. Or some merely use fine sandpaper, and work on it while watching TV.
 
This is all making me think that there is some misunderstanding about a "smooth patina." It sounds like it's as much a function of factory polishing as it is "years and years of cooking and seasoning," as is often stated. A smooth finish must depend on both, right?

Sorry if I'm beating a dead horse....
 
Rob, here's something else to consider. Last summer I sanded the cooking surface of a horribly pitted #7 skillet with a Piqua ghost mark. I figured since the pitting made it worthless anyway.... why not? I used 60 grit aluminum oxide and 100 grit silicon carbide sandpaper. Now the cooking surface won't hold seasoning worth a darn. Meanwhile the inner sidewall (which I did not sand) is nice and black. After sanding the surface was as shiny as stainless steel as opposed to the usual gunmetal grey of a bare vintage pan freshly cleaned after a lye bath or dip in the e-tank. Since I only used coarse sandpaper I suspect the lack of a magnetite layer on the iron is what's causing it to let go of its seasoning, as opposed to it being too smooth from sanding. One day I plan to revisit this problem and attempt to form a new magnetite layer.
 
You're right, I didn't consider the possibility of getting it so smooth it wouldn't season properly. Now I am wondering how smooth my two best Griswolds really were when they left the factory so many decades ago.

What is a magnetite layer?
 
Interesting theory, TyL, but I suspect incorrect. Prior to "pre seasoned" cast iron, none of the bare, gray iron sold had a layer of magnetite so I'm not sure why you think you removed it. If it had a layer of magnetite the manufacturers would never have put a layer of oil/wax on them to keep them from forming a layer of hematite (rust).
 
Factory polish grinding would vary from this:
polishgrind1.jpg

to something finer looking more like a brushed finish, to something quite smooth, the smoother finish being achieved simply by polishing it twice. Lodge offered three levels: plain unpolished, smooth, and "mirror" finishes. BSR did similarly with what they called plain and AA "double polished" finishes.

To me magnetite is the surface you get with bluing. I don't see it as a component of plain grey iron.
 
Good to know. And the polishing was done with a grinding stone? I f so, I would consider getting a small knife sharpening stone and trying that before sandpaper.
 
KevinE said:
Interesting theory, TyL, but I suspect incorrect. Prior to "pre seasoned" cast iron, none of the bare, gray iron sold had a layer of magnetite so I'm not sure why you think you removed it. If it had a layer of magnetite the manufacturers would never have put a layer of oil/wax on them to keep them from forming a layer of hematite (rust).
Click to expand...

All I know is that the portion I sanded looks nothing like the rest of the pan. What little seasoning there is never gets darker than light brown almost always leaves a grey residue on my CI drying rags. I assumed the grey iron I love to see come out of the e-tank/lye bath was the result of a thin layer of magnetite being allowed to form at the foundry since those pans have a cooking surface that's obviously machined yet has the same dull grey color as the sand mold textured exterior sides and bottom. I won't sand another pan, that's for sure. My #8 2016 Smokey Mountain Lodge got nonstick quickly enough just by using it.
 
RobHerrington said:
Ty, just curious ... how many seasoning sessions have you put that sanded pan through?
Click to expand...

Honestly, I'm not sure. I've stripped it at least twice but I probably piggybacked it with other cookware more times than that. Once stripped I typically put a pan through 2 coats of manual seasoning, followed by actual use to darken them up a bit.
 
I asked because I've read this woman's blog about the chemistry of seasoning,​ and she recommends about 10, as I recall. She sounds like a serious chemist, and as the old Allstate ad proclaimed, "They can't put anything on the internet​ if it isn't true."
 
RobHerrington said:
I asked because I've read this woman's blog about the chemistry of seasoning,​ and she recommends about 10, as I recall. She sounds like a serious chemist, and as the old Allstate ad proclaimed, "They can't put anything on the internet​ if it isn't true."
Click to expand...

She has degrees in psychology, counseling, and fine arts. Hardly what I would call a serious chemist.
 
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