Restoring a very rusty cast iron skillet using molasses and water

When Karl’s folks were moving house a few years ago, we looked after some of their plants and garden ornaments until they were settled. A few years on and some of the plants and ornaments are still with us, because they don’t have the outside space they used to. Among the pots, I came across an old cast iron skillet which had been part of a collection of other cast iron pieces; it looked quite attractive when combined with colourful planted containers. This skillet had been outside for some years and was now extremely rusty – I brought it indoors with the idea of one day trying to restore it and for a year or more it sat on a shelf in the hallway gathering dust.

1-skillet-before-1This is how the skillet looked before it went into the solution – click for a larger version

One day I came across the suggestion that rusty cast iron can be restored by soaking it in diluted black treacle. ‘What an extraordinary idea’, I thought, and immediately sought to find out more. There is indeed quite a lot of information about restoring rusty iron with black treacle (which from now on I shall call by its American name of ‘molasses’ because it’s faster to type) and the method is popular with those restoring engine parts as the molasses solution can get into all the nooks and crannies.

1-skillet-base-before-1The width across the base is 13.5cm

So, how does it work? I went to an all-girls school that didn’t see the need to teach girls chemistry and anything I do know about chemistry I’ve learned by myself,  so it took a little while to understand, but I did find this straightforward explanation: ‘Molasses contains chelating agents. These are made of molecules that are shaped a bit like the claws of a crab – the word ‘chelating’ comes directly from the Latin word ‘chele’, meaning claw. They can envelop metal atoms on the surface of an object, trapping them and removing them’ (a bit more here). Clear enough.

I don’t really mind that I wasn’t taught chemistry, or physics for that matter, at that school – it means I’ve spent many years playing catch-up, for sure, but it’s also given me a deep sense of awe and a strong desire to find things out and make connections between them. It means I’ve lived my life in a state of almost constant amazement at how the world works and that’s no bad thing.

holcroft-1The name Holcroft is just about readable

Thomas Holcroft & Sons Ltd was a foundry in Ettingshall Road in Wolverhampton which, amongst other things, made cooking ware for Agas. It was active from the 1890s until the business closed in 1969. From the very few pictures I’ve seen, I’m guessing this skillet might date from the 1930s.

I liked the idea of using molasses partly because I was curious, but also because although the method is slow, it’s cheap (£1.15 for 454g), non-toxic and once the solution is finished with it can be tipped onto the compost heap without causing harm. Lye had been suggested, but from all that I’ve read about lye it is very corrosive and has destructive effects on living tissue. There would also be the issue of disposal. I feared it would not combine well with my accident-prone tendencies and decided lye would be better avoided. Anyway, I wanted to see what happened during the chelating process.

molasses-tinI used two tins

The urge to test this molasses/chelating idea for myself was intense so I got some molasses right away, found an old washing up bowl and used the one part molasses to ten parts water solution commonly suggested, mixed it up, put the skillet in and left it to see what happened. Every two to three weeks I’d take it out, rinse it, scrub it vigorously with a wire brush, take photographs and put it back in to soak. Each time it came out of the solution more of the rust had gone and, to my unlearned eye, it was like some strange new magic – a sugary condiment that eats rust. I’d read that the solution would smell dreadful, but was a little disappointed. It certainly smelled odd and not something to keep indoors, but it wasn’t gag-inducing. Maybe it smells different in summer when the temperature is higher.

dilute-molassesThe solution did go quite murky and mould grew on the surface

So, here’s what happens when you soak a rusty skillet in molasses solution.

2-skillet-21-days-1After 21 days

3-skillet-33-daysAfter 33 days

4-skillet-45-daysAfter 45 days

6-skillet-55-daysAfter 55 days

skillet-before-2Inside the skillet before soaking

5-skillet-53-days-edgeThe same area after 55 days

5-skillet-base-afterI didn’t know the name was also on the base until I put the skillet in a hot oven for two hours to clean off the cooked-on crud

holcroft-3The name Holcroft is now much clearer

made-in-england-3The words ‘Made in England’ also appeared and there is a patent number which I think is ‘W6392’ but I can’t be certain as it isn’t very clear

The last process was to season it. I smeared the entire skillet with lard and put it in the oven at 160C for an hour. It was allowed to cool, wiped with a rag and the process repeated twice more until the fat started to bond with the iron and the surface looked less pitted.

 5-skillet-53-days-season-1After seasoning

Having given it some seasoning, I then cooked up a pan of dry-cured, fatty streaky bacon and not one bit of it stuck to the bottom. The bacon was delicious and really crispy.

So, not bad – it went from being extremely rusty to being quite presentable and usable again. Fair enough, it took nearly two months, but time wasn’t the issue. The issue was seeing what happened and the possibility of ending up with a usable cast iron skillet. I now need to find some more rusty cast iron skillets to restore.

4 thoughts on “Restoring a very rusty cast iron skillet using molasses and water

  1. Absolutely fascinating Miranda, I shall be experimenting with this method on some rusty old garden tools.

  2. Fascinating process. Thanks for sharing the results. I almost wish I had some rusty pans to try this on.

    1. I need more rusty pans, Patsy, and will be doing the rounds of charity shops!

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