Strip Cast Iron for Seasoning

There are many different methods of stripping old seasoning and rust from cast iron, here are a few that work for me and won't damage your cookware!

I use a multi-stage process. Which stages I actually use depends on the piece that I'm restoring

The main part of this section features processes that require some simple but special equipment, check out the DIYs section for instructions on how to build this equipment yourself. If you are only going to be stripping one or two pieces you may want to skip to the end for some more beginner-friendly methods that can be used with just a few supplies you can find at the grocery store.

Stage 1: Lye - For heavily seasoned cast iron

DIY: Build a Lye Bath
Skip To: Easier Version - Oven Cleaner

Note: Caution must be taken when working with lye. Wear heavy duty, long cuffed chemical resistant gloves, eye protection, and avoid any exposed skin on your arms and legs. Learn More about how to safely work with lye. Follow this guide at your own risk.

Carefully place cast iron in lye bath
Wait at least 1 day. Cast iron can be left in lye indefinitely and will not damage the metal
Carefully remove from lye bath and transfer to bucket or tote
Use a nylon scraper or brush to gently remove thick clumps of dissolved seasoning
Transfer to sink or outdoor area to be rinsed. Keep in mind that lye may damage or kill plants, so be cautious when rinsing outdoors.
Rinse well with cold water while scrubbing with steel wool and/or handheld stainless steel brush. Never use brass brushes, or any sort of power tool to clean your cast iron. You will cause permanent damage to the iron!
Repeat previous steps as necessary. If you are dealing with extremely stubborn seasoning and aren't in a hurry don't be afraid to leave your iron in lye for weeks or even months

Stage 2: Carbon Off - For stubborn carbon deposits unaffected by lye

Like lye, Carbon Off can and will cause damage if it comes in contact with your skin. Use similar precautions when handling Carbon Off, and be sure to read the entire label before use. Only use Carbon Off in a Well Ventilated Area!

In a well ventilated area apply a small amount of Carbon Off gel to the entire surface with a paper towel or paint brush. Carbon Off also comes as an aerosol spray, but my results with that version have not been great. I recommend sticking with the gel version
Lightly cover with aluminum foil
Wait a minimum of 30 minutes, up to 1 hour. Carbon Off will not damage the surface if left on for longer, but it may dry and become difficult to remove.
Remove aluminum foil and scrub with a handheld stainless steel brush. Do not over scrub or you may end up with light spots after seasoning. If the deposits are not coming off easily repeat the previous steps again
Rinse thoroughly with cold water

Stage 3: Electrolysis - For rust and old seasoning

DIY: Build an electrolysis tank
Skip To: Easy Version - Vinegar
Skip To: Easier Version - Evaporust

While thick seasoning can be removed with electrolysis, I find it more efficient to strip heavily seasoned and crusted pans with lye before this step. For pans without rust, you can skip this step if desired.

Using bare steel wire (I use rebar tie wire) wrap a few times through the handle
Hang the cast iron inside the electrolysis tank while making sure it is completely submerged and not contacting any of the anodes
Attach the negative lead to the wire attached to the cast iron
Attach the positive lead to your anode(s)
Double check that nothing connected to the negative lead is contacting anything connected to the positive lead. This includes the pan, anodes, and any wires
Turn on your power supply and check the amperage reading. You will likely see lower amperage than the charger is rated/set for but this is normal. If you aren't seeing any reading at all, check your connections between the leads and pan / anode(s). Dirty / rusty / old anodes will not work as efficiently and will lead to a drop in amperage
Within a few moments the cast iron should start bubbling in the water. This can range from a slight bubbling off the surface to a vigorous bubbling across the tank depending on amperage and anode condition. If you aren't seeing any bubbling then something is wrong, check your connections and amperage reading
Depending on the amount of rust or seasoning, the size, position, and condition of your anodes, and the amperage rating of your power supply this process may take as little as an hour or as long as a day or more. Check your progress from time to time and remove your cast iron once the rust is no longer visible or has turned entirely black. For heavily rusted or seasoned pieces you may want to remove and scrub them part way through the process and return them to the tank
Once all signs of red/brown rust are gone, remove your cast iron from the tank
Transfer to a sink or outdoor area to rinse
Using a steel wire brush and/or steel wool clean off any remaining residue. During the electrolysis the rust on your pan may turn black and remain fairly stuck to the surface, if this is the case scrub until no more rust is easily removed and place back in your tank for a bit longer
Your iron is finished when there is no more rust or seasoning remaining on the surface

Stage 4: Final Cleaning

Thoroughly rinse the surface of your cast iron
Use a fine grade steel wool (grade 1 or finer) on all surfaces until even and clean
Add dish soap while continuing to scrub
Rinse thoroughly with cold water
Use paper towels to wipe dry
If the paper towels are becoming very dirty during drying continue to rinse and scrub with soap and a sponge or nylon brush. You can also use a magic eraser at this stage
Once totally clean and towel dried place in a 350 degree oven for at least 15 minutes to dry completely

You are now ready to Season!

Easy Methods

These methods require less special equipment, using ingredients and tools available at your local grocery or hardware store.

Stage 1: Removing Seasoning

Oven Cleaner

Be sure to use regular oven cleaner, not fume-free. Check the active ingredients and make sure they include Sodium Hydroxide or Potassium Hydroxide.

Warning: Sodium Hydroxide is lye. Carefully read the instructions and warnings on the can before use and follow the same safety precautions as using a lye bath.

Supplies

Yellow Cap Easy Off or other full strength oven cleaner
Heavy duty garbage bag(s)
Long cuffed dish gloves with no rips or holes
Eye protection

Steps:

In a well ventilated area thoroughly coat your cast iron in a thick layer of Oven Cleaner. If you do this outdoors be mindful of the direction of the wind, you do not want a face full of Oven Cleaner!
Place soaked cast iron in a heavy duty garbage bag and seal tightly
Store in a warm place for at least one day
Carefully remove cast iron from garbage bag and scrub with steel wool and/or a steel brush. Lye soaked cast iron can be very slippery. Use caution handling it until it has been rinsed
Rinse completely
Repeat as necessary

Stage 2: Removing Rust

Option 1: Vinegar

Supplies

Distilled white vinegar
Water
Water-tight container large enough to completely submerge your cast iron
Steel wool and/or stainless steel brush
Dish gloves
Cast iron with no remaining seasoning

Steps:

Fill your container with a 50/50 mix of distilled white vinegar and water. Make sure there is enough to completely cover your cast iron, or you will end up with a permanent line where the cast iron wasn't submerged
Place the cast iron in the vinegar solution for no more than 30 minutes. Vinegar does a great job at removing rust, but it also eats away at the iron itself. In short doses it will not negatively affect the iron, but left too long it can cause pitting, discoloration, and can even make the iron brittle.
Remove from the vinegar and scrub with steel wool and/or a steel brush while rinsing
Repeat as necessary, but not for longer than 30 minutes at a time
Thoroughly rinse and dry once the rust has been removed

Option 2: Evaporust

Supplies

Water-tight container large enough to completely submerge your cast iron
Evaporust. Preferably enough to completely cover your cast iron in the container, but it can be diluted with water if necessary, although this may slow down the rust removal process
Steel wool and/or stainless steel brush
Optional: Dish gloves

Steps

Place your cast iron into your water-tight container
Fill the container with your evaporust
If your iron is not completely submerged, add water until it is totally covered. If it is not totally submerged it will leave a permanent line where the iron was exposed to the air
Leave for 30 minutes up to one day or longer. Cast iron can be left in Evaporust indefinitely without causing damage
Remove and scrub off any residue with steel wool and/or a steel brush. Gloves are not strictly necessary when working with evaporust, but the chemical process it uses to remove rust does have a fairly unpleasant odor, so they are not a bad idea either
Repeat as necessary

Note: Evaporust can be reused until it no longer works. Either cover your container or carefully pour the contents back into a storage container for next time.

Bad Ideas

Some ways not to strip your cast iron:

Power Tools. Yes, it's faster. Yes, it will also permanently damage the surface of your cast iron. Cast iron stripped with power tools is easily identifiable by a bronze/brown coloring after seasoning, uneven surface texture, and gouges/marks from the tool
Sand Blasting. Similar issues as power tools. You are significantly altering the surface when sand (or other media) blasting iron and it will affect the way the pan looks, seasons, and performs
Fire / Hot Coals. Many people swear by this method, but it carries significant risk of permanent damage. Fire damage is the bane of cast iron collectors and restorers. A fire damaged piece will be weaker, with potential for surface damage, discoloration, warping, and increased brittleness. Many fire damaged pieces have a reddish/pinkish hue on the entire surface or in smaller areas when stripped. It may look similar to rust, but often has a deeper shade of red or pink.
Self Cleaning Oven. This has similar risks to using fire. While you likely won't end up with the same level of severe damage, it is not uncommon for pans cleaned this way to warp or become difficult to season. It's also a fire hazard!