Most of this information is presented within the Cast Iron Pan – Restoration section of this website – but I wanted to have a place that people could comment on this specific topic. I know that people into Cast Iron have wonderful and often loud opinions!
If the thought of restoring an old and ugly cast iron pan scares you – I would like to offer a few words of encouragement. Follow these simple steps and you will see that it is not too difficult. And let me tell you a secret. You do not need to be perfect. Cast iron is strong and durable and as long as you do a moderate job – you will be fine.
Re-Seasoning vs. Restoring
Beginners may get confused by the terminology here. Re-seasoning is when you build an initial seasoning onto your pan by baking a couple layers of oil onto a bare iron pan. Restoring is when you strip that pan down to the bare iron through a few different methods. In fact, restore first and re-season after. You can find all the seasoning information you want in the Initial Seasoning section.
When do you make the decision to strip a pan and start again?
Maybe you have an old pan that someone gave you, or maybe this is a pan that you bought at a second-hand store, or maybe you found it in your basement. Surprisingly enough…maybe it is a brand-new pan and you don’t know or trust the initial seasoning. Let’s look at some examples.
If you have an old rusty pan – take a close look at it. If you see what seems to be just surface rust – give it a good scrub. Another good idea is soaking the whole pan in a large sink or tub with a 1:1 mixture of vinegar and water. Let it sit for a couple hours and that alone may remove most of the rust. Use a Scotch-Brite green scouring pad or a steel Chore Boy and give it a good scrub. It is possible that may be enough to revive the pan. Then re-season and you are good to go.
But maybe the rust is more pervasive or there is old, baked-on food stuck to the pan. There is no escaping the fact that it all has to come off and you have to take it down to the bare iron and start again. Don’t worry – it is not too difficult and we will review how to do it in just a moment.
If you purchased a used pan and it is already seasoned – you still need to take a close look. As explained above, if you see rust or food – you will have to restore it and re-season. If it is clean but seems sticky – better to restore it. That stickiness is someone’s poor attempt at an initial seasoning. You have to strip it and start over. You will not be happy with it.
But if the pan passed all those tests and it looks good – give it a light scrub and try to cook with it. Get some butter or oil in the pan and see how it behaves. If you are satisfied, then you are good to go. Using the pan will improve the seasoning over time or you can put a few additional layers of seasoning on it as explained in the section of seasoning.
The same goes for a brand-new pan. Don’t assume that a new pan will have acceptable seasoning. Cheap imported pans may have an initial season that will only cause annoyance and trouble. If you are not satisfied with the performance then better to get rid of it and start again.
But by the same respect – don’t assume that it will be bad either. If the seasoning looks good – try it out. Reputable manufacturing companies will spend more time and effort with the initial seasoning before they ship it. I was recently faced with this situation with the purchase of my first carbon steel pan. It stated it was “pre-seasoned” – and the blog post on that experience is coming soon!
So how do you restore a cast iron pan?
If you have determined that you need to strip the pan and start again you have a few options. The most common ones are listed below.
The easiest, as mentioned above, can be a good scrubbing with a vinegar soak. Your goal is to get all the rust off and trust the seasoning below it is still ok. This method only works if the pan is lightly rusted. But my preference is to take it one step farther.
That next option is a lye treatment – also known as your friendly everyday oven cleaner. The standard product used for this task is Heavy Duty Easy-Off oven cleaner. Well, maybe “friendly” is not exactly the right word. This oven cleaner contains lye, also known as sodium hydroxide or caustic soda, and you absolutely need to be careful. It will strongly react to anything organic – which is why it cleans baked-on food from the pans. Click the hazard identification diamond below or here for the Safety Data Sheet. It shows that the product contains 2.5-10% lye. Please take all necessary precautions described on the can. You don’t want it on your skin and certainly not in your eyes. Some other oven cleaner products are made to be low odor and they use ingredients other than lye. You want the Heavy Duty can because it does contain lye and it does the job. 
The oven cleaner is easy to use. Using gloves, spray the entire pan (top, bottom, handle) then place it in a closed trash bag for a couple hours to a couple days. The trash bag will keep it from drying quickly. In my personal experience, sometimes I have checked on the pan and reapplied with an additional coat of oven cleaner. This method has never failed me. It will do a really nice job to remove just about everything from its past life.
When you check it – give it a scrape and once you feel the old junk is softened then it is time to wash it off. Again – use hand protection and be careful with the lye. Use lots of water to rinse the pan then give it a good scrub. Use a Scotch-Brite green scouring pad or a steel Chore Boy. You will find everything comes off pretty well.
The oven cleaner will remove much of the gunk covering the pan and it is the only method I use. However, I am not a cast iron collector and I do not resell pans. I am an avid cast iron user. My pans are loved, well cared for and used everyday because they are an essential kitchen tool. I treat them carefully, but I do not baby them. I state that fact because when I restore a pan I use oven cleaner and it gets mostly everything off. If you want to restore an old pan to clean bare iron and bring back its former glory from 60+ years ago – you may want to try the next method.
Just add electricity
In general terms, this method uses a plastic tub large enough to suspend your cast iron pan. You fill that tub with water mixed with sodium carbonate (Na2CO3) and that acts as your electrolyte solution. The system needs 2 more things. You need to incorporate another piece of metal to act as a sacrificial anode – a piece of rebar, for instance. The anode is called sacrificial because you are literally forcing it to corrode instead of the pan. The last ingredient to this mix is electricity. By correctly hooking up an electricity source (like a car battery charger) you can produce an electrical current flowing from your pan to the anode.
If you are interested in this method – I strongly encourage you to follow the safety precautions and the instructions carefully. As I mentioned, this is not my preferred method so I will rely on others when it comes to explaining each step. People have been using this method for many years and they restore not only cast iron pans but also old woodworking tools, horseshoes and other iron objects.
A word on sandblasting, wire cup brushes, sandpaper and grinders
The methods explained in the above sections involve some hand scrubbing, chemistry and electrolysis. You can also choose to take the aggressive, physical approach. If your pan is covered with unwanted rust and crud – you can choose to sandblast it off. That works too but it might leave some marks if that bothers you.
Other physical methods would be a grinding wheel or a steel wire cup attached to a drill. These things can work alone or in conjunction with the methods above. But they also have a tendency to physically alter your pan. Grinding marks and swirls left on your pan are a real possibility. A professional restorer or a collector would rarely suggest these methods.