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Created April 19, 2018 21:24
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Cast Iron Repair
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cast_iron.md

Cast Iron Repair

This guide covers cast iron repair, cleaning, and re-seasoning. Different tools are needed depending on how bad a shape the cast iron is in.

Tools Needed

If you are only cleaning and seasoning the pan (that is, there is no rust), you will need:

  • A calibrated oven with "cleaning cycle" capabilities
  • A lint-free rag you don't mind ruining (or using just for this purpose)
  • Scott's Shop Towels (you can get these at HomeDepot; don't use regular paper towels)
  • A sponge with a rough side
  • Steel Wool, preferrably 00 Grade, or Regular SOS Pads
  • An acceptable seasoning oil; from favorite to least-favorite:
  • Distilled Vinegar (only if you are planning on taking more than 1 hour between the cleaning and seasoning steps - must be enough Vinegar to completely submerse the cast iron)

Note: your oil choice is important; do not use anything that is "refined" (which may not be labeled) or anything that has a smoke point over 380F.

If you need to remove rust from your pan, you may need to buy the following, as well (see section 2 for details):

Method 1

Method 2

Method 3

Steps

1. Clean the Pan with the Oven Cycle

  • Remove all items from oven other than what is part of the oven (shelves, etc)
  • Place the pan, upside down, in the oven, so that the cooking surface of the pan faces the floor of the oven
  • Close the oven door (and lock, if necessary) and follow your oven's instructions to clean for 3:00 hours

Wait for the oven cleaning cycle to finish and for the oven to completely cool.

At this point, your pan will likely be a shade of red with powder on it that is VERY easy to knock off. Be very careful when transferring this pan to the kitchen sink.

  • Move the pan, still upside down, to the kitchen sink
  • Shake off any loose powder or residue into sink
  • Use the sink to wash away any powder and residue that is still stuck to the pan

At the point, the pan should look a much-brighter grey than it did going into the oven, but will likely still have pockets (or lots!) of red on the pan.

  • Use dish soap and the SOS pad (and sponge, if needed) to remove the red marks on the entire pan, including the handle and back
  • Ensure all red marks are completely gone and the pan is a dull grey color

If, at this point, there are rust spots that are very hard to reach, submerse your cast iron in distilled vinegar and allow it to sit overnight. Ensure the entire pan is covered, or the areas uncovered will quickly rust from moisture in the air.

Note If, for any reason you are not immediately going to season your pan, it is vitally important that it be stored under vinegar until seasoning time. Unseasoned pans will rust as soon as one-hour after cleaning without their protective coating.

2. Remove Rust

Note If your pan is not rusted, you can skip this step and move on to Seasoning

Only apply these steps to areas with significant damage. You are removing metal during these steps, and can damage or limit the life of your pan. Try steps, in this order, from least-damaging to most-damaging to try to remove rust:

  • Vinegar Method:
    • Soak the cast-iron in Distilled Vinegar for an extended period of time (24-48 hours)
    • Srub off rust with a scouring pad and steel wool regularly

If you ever see people recommending another acid, like Coca-Cola - don't - it's more expensive and doesn't work as well. Stronger acids will damage your pan significantly. Stick to Distilled Vinegar.

  • Electrolysis Method:
    • DO THIS OUTSIDE OR IN A WELL-VENTELATED AREA
    • Fill a plastic bucket large enough to hold the cast iron with plenty of extra space
    • Add about 2/3 cup of baking soda per 5 gallons of water to the water as an electrolyte; stir well
    • Add a scrap piece of iron (e.g., rebar) to one side of the container so that it is sticking out of the bucket
    • Using a wire hanger and a metal across the bucket, hang the cast iron so that it is completely floating (not touching sides or bottom) in the bucket
    • Attach the negative (black) alligator clip of the car jumper to the wire holding the cast iron sticking out of the water
    • Attach the positive (red) alligator clip of the car jumper to the piece of rebar
    • Power on the rebar and watch for bubbles near the top of the wire

This method tends to remove rust selectively, so you will need to occasionally move the Anode (the red clipped rebar) around in the water to remove rust evenly. Ensure that the metal parts NEVER touch, or you will cause a short and may damage your power supply. This may take some time!

  • Polishing Method:
    • Attach a wire brush to your drill
    • Wear eye, hearing, and breathing protection!!
    • Clamp the cast-iron somewhere sturdy and use the wire brush to remove the rust on the pan until you see a dull-grey surface
    • Wash the pan several times with soap, sponges, and water to remove the silver resude left behind thoroughly (this can be a huge pain)

3. Seasoning

Seasoning a pan is the process of putting an extremely light layer of oil on the surface of the pan and baking it in past its smoke point. This provides a clean, non-stick surface on the pan. However, doing this inaccurately can cause unsightly pans, seasoning that can chip off with use, and other problems that can be avoided by using these instructions.

  • Pre-heat the oven to 200F. Do not put the pan in the oven during this process, as gas ovens, especially, release significant water during pre-heating and can flash-rust your cast-iron
  • Once pre-heated, place the cleaned pan in the oven upside down for 15 minutes

At this point, it is highly recommended to use a well-made oven mitt when handling the pans in all steps past this point:

  • Open your grease container and prepare your lint-free rag; melt the grease if that is required (e.g., bacon grease, coconut oil)
  • Remove the pan from the oven and place, right-side up on the stove top
  • Dip the rag in your grease and apply a light layer to the entire pan, including the back, sides, handle, and inside the handle hole (do not pour grease directly into the pan)
  • Once covered, take a folded Scott's shop towel and wipe as much of the oil out of the pan; the pan, when done, should be shiny but not wet
  • Increase the oven temperature to 300F
  • Place the pan, upside down, in to the oven for 15 minutes

This will warm the pan to just-under the smoke point of the oil, allowing it to penetrate into the pockets of the metal and pool any extra oil so it can also be removed.

  • After 15 minutes, remove the cast iron from the oven
  • The pan at this point will likely have a splotchy, motted look - this is excess oil that has pooled in the iron; if you do not see this motted look, try replacing the pan in the oven for another 15 minutes at a slightly-higher temperature (look up your oil's smoke point for reference)
  • Using a fresh Scott's shop towel, wipe generously across the whole pan to remove any excess oil that accumulated, removing the motted look
  • Place the pan, upside down, back into the oven
  • Increase the oven temperature to 400-450F for 2:00 hours - this will cause smoke, and a fan or window should be used to remove it

After 2:00 hours, the pan can be removed. It is very important that no cold liquids (e.g., water) touch the pan until it has air-cooled to room temperature.

  • Feel the pan - it should be smooth, black, and not be tacky or sticky
  • If the pan is sticky, try repeating the bake-in process for another 2:00 hours at a higher temperature
  • If the pan is still sticky, you may want to try another oil or ensure you're being extremely thorough when wiping excess oil off at each step (did you skimp on the Scott's towels? They're made for oil!)

After cooking a few times with your new cast iron, the seasoning will build up more and more layers, helping to add to the non-stick.

THE MOST IMPORTANT NOTE After seasoning, NEVER wash your cast iron with soap. Use warm water and a scrub brush to remove elements on the pan, and the non-stick nature should see that they fall right off. If the pan has problems with non-stick, you may want to re-season the pan or find a pan with a less-coarse texture while you continue to learn to cook with cast iron.

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