Ok, so somebody (me) put a cast-iron pestle and mortar in the dishwasher, before reading the instructions, which say it must not be put in the dishwasher.
:smack:
Yes, I know iron rusts, but I (wrongly) assumed that such a product would have been protected with some anti-rust agent, or it would start rusting the second you put it in water.
So stupid behaviour aside, now the thing is rusting. Is there any way to save it?
I see a number of articles on coating (seasoning) cast-iron skillets, which involves oil and heating, but can the same principles be applied to a mortar?
They might, provided a coating of heat polymerized cooking oil is what you want. If it had much of a coating of any kind I don’ t think the dishwasher would have rusted it so quickly. I’ve never heard of one of cast iron. Is it used for cooking?
I would season it just like a pan. First you’ll have to use steel wool to clean off all the rust. Then take your pick of the articles, they’re similar but everyone has their own twist. Generally you coat with vegetable oil then put it in the oven for a while. Then do not use soap to wash it, just a wet sponge or scrubber, and occasionally coat with oil.
I’ve never heard of an iron one, either. Yes, uncoated iron will rust when exposed to water, it seems like it should have come with some instructions as to how to coat it or season it.
Yes, it’s a cooking utensil. Made by the renowned Swedish iron foundry of Skeppshult. They’re the only one in Sweden, so I suppose cast-iron mortars aren’t that common.
And I guess I blew my “25 Year Cast Iron Guarantee” now.
There’s nothing in the instructions about how to season the thing, but the little booklet does say that their products are “lightly seasoned with vegetable oil”.
I will try the wool, oil, heat treatment and see how it goes. Thanks, all.
Similar thing happened to me. I bought a cast iron skillet and, of course, washed it before using it. The whole thing rusted. (Now I know why it was such a great deal)! I scrubbed with steel wool, washed again and dried immediately, coated with veggie oil, put in oven 350 degrees. After one hour, I shut off heat and let skillet remain until cooled. I did it several times. Now the skillet is a beautiful shade of black. I wipe clean with wet sponge and dry immediately.
I suspect same technique will work for you. Be prepared to have a smokey kitchen while seasoning.
SweetP, those are comforting words, thanks. I hear peanut oil is particularly good due to its high smoke point. The most heat-resilient oil is apparently refined avocado oil, but I’m not sure if it is appropriate for seasoning.
I had a friend who used to collect iron skillets (?!?) and would bring them to a bonfire party, then throw them in the fire for an hour or more (or until the fire died out). She swears that it keeps the iron from rusting.
Frankly, I’d stick to the vegetable oil and oven routine.
Though a good seasoning makes cast iron almost stick-proof, even the best ‘seasoning’ can not stop oxidation from occurring eventually with normal use; and certainly is useless v. a dishwasher which soaps off the greasy protection and then subjects the iron to hot water – that’s a guaranteed rustfest. The great thing about cast iron is that you can just abrade off anything that might stick to it, including any rust, and re-season.
The OP asked about a pestle and mortar, not a skillet. I presume it’s not designed to be put on fire. Are you guys sure it’s supposed to be seasoned with oil?
I’d contact the manufacturer and ask. It can’t be the first time it happened.
The seasoning process is the same for all cast iron cookware, including mortars and pestles. See here for the procedure. Remove the rust first with steel wool and much elbow grease.
scr4, actually the little booklet that comes with the pestle and mortar does say that the company’s products are “lightly seasoned with vegetable oil”.
The mortar may not have been designed to heat food, but it’s still an iron alloy, the components of which presumably don’t change shape in an oven at semi-high heat.
I’m not a cast-iron expert, and perhaps skillets are like this, too, but the mortar, at least, is of a very coarse material – it’s not smooth, but rather rough, as if sandblasted, a pretty mix of black and silver.
At my museum, we use a very fine steel wool, much softer than your average Brillo pad, because highly abrasive steel wool can leave scratches. We then dip the soft steel wool in mineral oil, and rub gently to remove rust. On non-food related items, we sometimes use paint thinner to take rust off metal items, but in your case, I’d stick to mineral oil, or something else edible.
