Restoring Cast Iron Pans part 1: Theory and methods

At some point, whether through inheritance, shopping, or neglect, you are going to need to restore a cast iron pan so that it is usable again.

There are two major items that can make a cast iron pan less than usable: Rust and crud. A number of methods have been devised over the years, and this article aims to help with selecting an appropriate method to restore your pans.

Removing Rust

Rust, a buildup of iron oxide (Fe₂O₃) happens when cast iron pans are exposed to water or humidity without being dried properly.

Electrolysis

Electrolysis is a process by which electricity is used to remove rust. Effectively, you immerse cast iron in an electrolytic solution and pass electricity through it, removing rust by attracting it to a piece of disposable metal.

In an electrolysis tank, you submerge a piece of metal (known as the sacrificial anode) in your tank (which is a solution of water and washing soda) and connect it to the positive (+) lead of a manual battery charger. Usually plain steel or graphite are used for the anode. Next, you connect the negative (-) lead to the item being cleaned. Next, you apply current to begin the process. The rust that is on your pan (or other item being cleaned) will be attracted to the anode. (As shown by the lovely arrows in my illustration). Electrolysis is a directional process, and only the side of the pan facing the anode will get cleaned. You can periodically rotate the pan to clean it or use multiple anodes to surround the pan on all side.

While you can get crazy with an electrolysis tank, a very basic setup requires not much more than about 40-50 dollars in parts. Many of the parts needed for an electrolysis tank are household items, so that is another way to keep costs down.

Electrolysis tanks are single-handedly the best tool for restoring cast-iron pans as they low-maintenance, safe enough to use on cast-iron which is of collector quality, can clean both crud and rust, and requires very little actual manual work.

To build an electrolysis tank, you need a STURDY bin (read: not a clothes bin / Rubbermaid), a few clamps, some scrap metal (Crappy old steel baking sheets are great here), washing soda, and a manual charger (such as one made by Schumacher).

Regarding the bin, it is important to note that water is HEAVY. At 8 lbs per gallon, it will bend most thin-walled vessels and eventually topple the vessel. I learned this the hard way. Also washing soda is sometimes hard to find. In a pinch, you can convert baking soda (Sodium Bicarbonate) to washing soda (Sodium Carbonate), by spreading it thinly on a cookie sheet, at no more than about 1/2″ deep, and baking it at 400 degrees for 30 minutes, stirring it every 10.

You can get really exotic and build all kinds of cool wiring and methods to surround your pans with anodes (since the process of electrolysis is directional), but for a starter e-tank, you’ll just have to rotate the pan periodically so that the side of the pan being cleaned faces the anode. Once you got the kinks worked out (and you understand the science) you can get fancy.

Vinegar bath

A solution of 50/50 plain white vinegar and water makes a fairly effective solution for the removal of surface rust. You can soak a pan in this solution for 25-30 minutes which will loosen up a good deal of the rust. Then scrub it with a scouring pan and repeat as needed until the rust is removed. A vinegar bath is very useful as it requires no permanent investment in equipment, but it is not the most efficient way of removing rust.

Removing Crud and organic matter.

Removing crud and various baked on organic matter from pans is best done with Lye (Sodium Hydroxide). Lye is a very useful chemical used in the production of soaps, pretzels, bagels, and hair relaxers. It is also the main component of drain cleaners, and appropriate for cast-iron work, oven cleaner.

Note: Lye is pretty caustic, so make sure you use proper Personal Protective Equipment (PPE), such as long gloves, eye protection, and an apron when working with it.

Oven cleaner + trash bag method.

One simplistic way to remove crud from pans is to use spray on oven cleaner + a trash bag. You spray the pans liberally with the oven cleaner, and seal them in a contained vessel (such as a trash bag) and let them sit for some time to allow the lye in the over cleaner to loosen and/or dissolve the organic matter. Lye works better in warmer temperatures, so if you can, place the trash bags in direct sunlight for maximum effect. If you are space constrained, or if you don’t want to commit to having permanent infrastructure for pan reconditioning, this solution works.

Lye tank

An alternative method to using oven cleaner + trash bags, is a lye tank. A lye tank uses the exact same principles as oven cleaner, but does it at a much larger scale. To create a lye tank, you need a vessel which can hold water (such as a large bucket), fill it with water, and then add lye crystals (at the proportion of 1 lb of lye to 5 gallons of water). Next stir it up, add your pans to the lye tank and walk away. Let the lye work its magic. Don’t rush it. Every 24 hours or so (read: whenever you get time), rinse them and scrape off whatever gunk you can with a stiff wire brush. Again, lye works better when warmer, so in some exotic setups, folks add fish tank heaters to their lye bath to improve the efficacy of the solution. I’ve considered this for my lye tank, but I live in a warm weather climate and haven’t seen the need for it. If you live in a cold weather climate, this might be a more appropriate upgrade. Note, with a lye tank, it is strongly suggested to use a container with a lid. Lye is pretty caustic, and you wouldn’t want kids, pets, or overly inquisitive spouses getting into it.

I prefer the lye tank, because it is cheaper in the long run. For the cost of 4-5 cans of oven cleaner, you can purchase 2-4 lbs of lye and make a solution that literally will last forever.

Listed below are my two lye tanks. A smaller 5 gallon tank and a larger 20 gallon tank.

Other methods

Self cleaning oven and/or fire

Other methods that I are used to remove crud from pans include using the self cleaning setting of an oven or simply building a fire and burning off the crud. I do not recommend these methods for the following reasons.

– They aren’t that precise with regards to applying heat. Cast iron can warp at high temperatures (> 900-1200 degrees) – One generally does not know how hot their self-cleaning ovens or fires are. (See previous statement). – While cast iron can withstand rather high temperatures, it is sensitive to temperature shock. (Either rapid heating OR cooling) – Running the self-cleaning cycle of an oven is one of the harshest things you can do to an oven. Why put all that wear and tear on your oven and shorten its lifespan? – Lastly, burning off your seasoning/crud with the oven means your house is going to smell horrible.

Given the above reasons, I believe those methods are too risky. This is doubly so if you are restoring antique/heirloom cast iron. It would majorly suck to have finally found your grandmother’s set of Griswold pans that have been around since FDR was president, only to ruin them in an attempt to restore them.

Practical Application

Ok, now that you understand the methods, how do you know which method to use and when?

Listed below is the checklist that I use when restoring.

1. If it is a pan that is exceptionally cruddy, use one of the crud removal techniques (lye tank or spray lye + trashbag). Leave the item in the lye tank or trashbag (whichever you are using) for a day or two.
2. Remove pan from lye tank or trash bags, rinse, scrub,
3. If necessary repeat steps 1 & 2
4. Move on to rust removal. Put the pan in the electrolysis tank or use the 50/50 water/white vinegar scrub to remove rust.
5. Remove pan from e-tank or vinegar bath, rinse, scrub.
6. Repeat step 5 as needed. (Though if you are using an electrolysis tank, you _rarely_ need multiple sessions)
7. Preheat your oven at 200-225 degrees F
8. Dry the pan EXTREMELY well & bake in the oven for 20 minutes (you are just getting it very dry and opening up the metal).
9. Remove pan from oven, immediately apply a thin layer of whatever fat you plan to use to season the pan.
10. Season pan using your favorite method.

You are probably asking yourself, which do you use both a lye tank and an electrolysis tank if the electrolysis tank can remove both crud and rust? The simple answer to that is that I am cheap and it is a matter of efficiency. A lye tank costs zero (after the initial setup cost) for it to perform its job. An electrolysis tank costs both electricity and the cost of sacrificial anodes. By letting the lye tank remove the organic matter, I can keep the electrolysis tank as efficient as possible and only burn electricity for rust removal.

Additionally, the lye tank is my ‘holding tank’ for new pieces that I need to work on. It has significantly more capacity (I can easily hold 8-12 pans in it) than an electrolysis tank.

Now that you understand the methods for restoration, our next two articles will cover building a lye tank and building an electrolysis tank.