So you just got yourself a cast iron skillet and you're eager to finally start using it, but as you wipe it down, you notice you're collecting a ton of black residue on your rag.
What is this black residue on your cast iron and do you need to get rid of it?
Well, it depends.
If you acquired your cast iron skillet used, then this black residue is likely nothing more than carbonized oil, charred food, or flakes of polymerized oil – none of which are harmful.
However, if your cast iron is brand new, the black stuff is likely the preseasoning that was used by the manufacturer.
Regardless, it's always better to just get rid of it so that you know exactly what you are cooking into your food.
So let's put your mind at ease and cover three ways to clean black residue off cast iron so you can put a fresh seasoning on your skillet and start anew!
Other awesome cast iron guides!
Alright, so the first method is to use a self-cleaning oven – if you have one – to incinerate any layers of oil or gunk and leave behind nothing but beautiful iron.
Step 1: Move all of your oven racks to the very bottom and place your cast iron skilled upside down on the topmost shelf.
Step 2: Start the self-cleaning cycle on your oven.
Step 3: Wait - the self-cleaning cycle takes 4 hours on most ovens.
Step 4: Wait some more – once the self-cleaning cycle is complete, let your cast iron sit until cool.
Step 5: Take it out and give it a good scrubbing to ensure there is no leftover soot and that everything is clean.
There you have it! A clean cast iron skillet free of that nasty black residue.
While this is a very popular method, self-cleaning ovens get VERY hot and do have the potential to crack your cast iron, especially older skillets.
So use this method at your discretion, or if you are looking for something less risky, consider the next few techniques instead.
And if you do go the oven route, just don't do it very often.
Probably the most popular way that many people use to clean cast iron is salt!
Salt is an awesome abrasive that is also very cheap and available. However, salt is typically used to clean cast iron when you don't want to break through your polymerized layer (seasoning.)
So, in addition to using salt, we are also going to use some soap to help break down the oil and get rid of that nasty black residue!
Step 1: Pour about a quarter-cup of kosher salt and some dish soap into your cast iron skillet.
Step 2: Using a washrag, scrub the inside of your skillet exceptionally well.
Step 3: Once you are done scrubbing, wash it using hot water. You want to try your best to get the soap out of the iron pores.
Step 4: Towel dry and then stick in the oven or on the stovetop with low heat to help evaporate the remaining moisture.
Because you are going to be reapplying the seasoning, don’t be afraid to really dig in as your scrub. This is one of the awesome benefits of cast iron - you can scrape it down to the bare metal and start anew.
Last up is the vinegar method!
Vinegar is very acidic and does a fantastic job eating away at any oils on the surface of your skillet – which is also a reason that you shouldn't cook with it once your cast iron is seasoned.
Step 1: Mix equal parts of white vinegar and water and completely submerge your skillet into it.
Step 2: Let it soak for about an hour and then pull it out.
Step 3: Give it a good scrubbing under hot water and then re-submerge it back into the vinegar.
Step 4: Let it soak for another hour and then scrub it again.
Step 5: Repeat the process of soaking and washing 2 to 3 times.
Step 6: Towel dry and then stick in the oven or on the stovetop with low heat to help evaporate the remaining moisture.
If you don't have a sink big enough to soak your entire pan, pouring the water and vinegar mix straight into the pan also works.
Be very careful not to let your cast iron soak too long as vinegar can begin to eat away at the cast iron and cause something called "pitting."
If you are just trying to get rid of black residue, soaking your cast iron for 2-3 hours should be more than enough.
Now note that each one of these methods is stripping away the polymerized layer of oil that protects the pan from rust and gives it that impressive non-stick surface.
So after following any of the steps above, you will need to completely re-season your pan.
There are also a ton of other ways to clean your cast iron – from scrubbing it down with chainmail to using boiling water.
If one doesn't work, try another – or even combined a few for a power-packed cleansing.
And know that even the best cast iron skillets will build up black residue, and no matter what you do, there is always going to be some residue or oil.
I hope that this little guide was helpful, and if you have any other excellent methods to clean black residue off cast iron, throw them in the comments below!