I bought a small cast iron pestle and mortar today. It has a black
finish which isn't paint. It looks thinner than paint. Does anyone know
what the coating's called and how it is applied? Just curious.
It depends. If it is food grade cast iron the finish is likely regular
corn oil that was applied while the piece was hot. Same process Lodge
Cookware uses on there cast iron. Seasons the surface so it becomes
If it isn't food grade then it could be simply thin paint. We used a dip
tank and THINNED black epoxy to do axles for Garden-Way products. That
stuff looked like black water it was so thin.
I've never seen a cast iron mortar and pestle, but the coating on cast
iron cookware is burned oil or grease which you build up over time.
A new skillet which is actually grey can be turned black by coating it in
oil or grease and burning it in the oven.
I've found olive oil works the best, but it takes more than one
application and some actual cooking to get it completely black. As is
claimed, they really to get better with age.
Yep. You mix the epoxy to spec, then thin it with acetone to the
viscosity you want. Once the acetone flashed off the epoxy started to
cure. Our normal procedure was to dip the axle then hang it to drip off
excess. Then once the rack was filled it went into an electric bake oven
for 15 minutes to drive off the acetone and speed the curing. Same
procedure used in a lot of places for a fast cheap anti-rust finish.
Then we also had the opposite spectrum of finish. The throttle bodies
and cover plates for the hottest 'Vette engine made in the 90's. The
ZR-1. All the throttle bodies and cover plates were painted in our shop.
They were a REAL PIA though. Degrease then masking on the bodies while
the covers went for a spin in the tumbler. Then the bodies came out for
powder coat. The covers went in and were sprayed with a base coat of
argent epoxy with texture added. Then the plates were hand filed to
surface the lettering and then sprayed with a clear epoxy with a
flattening agent in it. Then baked to cure.
Thanks for the opinions. It doesn't look like paint or lacquer. It's
really thin and hard. But I'm not sure it's corn oil either, because it
doesn't feel greasy. Does corn oil feel greasy even after baking?
Cheap labor is one but the other was that GM and Mercury Marine spec'd
them to be hand filed. PIA to do but they sure did look good. Plus it
was a VERY limited run of cars so we only did a few runs.
Now EGR valves on the other hand...... I can still powder coat them in
my sleep. Same with antenna masts and trim caps.
I guess the real question, not seeing it, is does this coating look
just like the coating on "pre-seasoned" cast iron pans in the camping
or cookware aisle?
It's probably just standard "seasoning" as people are saying. Oil
burned into the nooks and crannies of the cast iron. It requires
maintenance, and never wash it with soap or anything thats seen soap.
I use a lot of cast iron in my cooking. I have 2 cast iron pans and a
double sided skillet. As well as a nice Enamel coated dutch oven.
As the vegetable oil begins to oxidize, it first gets thick, then very
sticky, and finally it oxidizes completely and takes on a property something
like baked linseed oil. In fact, it's probably about the same thing. It
feels completely dry.
Some iron cookware used to be sold black, pre-cured. I have some French
steel sauté pans that came that way, which we bought 30 years ago, and one
heavy cast iron Dutch oven, bought 40 years ago, that were sold in that
I also have a large cast iron skillet, close to 40 years old, that was so
encrusted that I sanded it all down to metal with an angle-head sander (not
as easy to do as you'd think). Within two months of regular re-curings, it
was black again.
While my wife was on a business trip overseas (time to play ;-) )
I took a scrap cylinder of Stainless I had and dipped it into
30 wt motor oil, put it into a try (shop tray) and put it into our
Propane gas stove. Selected CLEAN oven mode and went about cleaning.
The smell was just a little worse than normal - as the splattered grease
was smoking also.
The color was liquor brown and nice looking. It was within the surface
as a thumbnail could not detect the edge. I sponged out the oven and
cleaned up my tracks - back to the shop - experiment done.
Think small heat treating oven - get red hot and slowly cool.
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
Motor oil probably had almost no effect here - first off, it does not
behave the same way as vegetable oil, and second you get a nice range of
colors on stainless simply with heat and oxidation - just hit a shiny
scrap with a torch to see the available range of colors.
Too hot. Well past that nice brown. More of an ugly gray. Stainless
colors at different temperatures than steel, for which the oxidation
color ranges are fairly well known due to blacksmiths using them as a
A typical home oven on clean gets to somewhere in the 700F range, as I