What Are These Carbon Steel Splotches?

This Matfer Bourgeat pan picture is one of the photographs that accompanied a question on Redditt.

One of the visitors to Redditt posted this question..”What are These Splotches?”

I have had these same splotches on a couple of my carbon steel pans. Without physically looking and touching the pan itself this is what I can come up with as the cause of these splotches.  If you look closely at the red arrows on the picture above, you will see that the splotches do not cover the whole pan, only parts of it.

It would be a good idea to run your fingers on the inside bottom of the pan and the sides of the pan to see if those splotches feel rough. After a properly seasoned pan, it should feel smooth everywhere on the pan.

What Can Cause Carbon Steel Splotch Patterns?

  • Inadequate washing of the pan before seasoning it could have caused this splotching
  • Improper food removal did not occur in the prior cleaning process
  • The pan was seasoned with multiple coats of Flaxseed oil which were put on too thick between coatings
  • The pan was seasoned but for some reason, the season did not “take” (unlikely)
  • The pan contained acidic foods in the cooking process
  • Oiling the pan was absent before cooking
  • Lightly oiling the pan was absent after cooking.
  • Pre-heating the pan did not take place
  • Or, this might be normal for this pan (unlikely)

Lets’ take a look at this a little further.

  1. Not washing the pan before it was seasoned could result in what you see in the picture. The carbon steel pan has to be thoroughly cleaned and dried before any seasoning process begins.
  2. If the pan was not cleaned entirely and oiled and then used the next time this could cause a build-up of food or splotches.
  3. If you are cooking acidic foods like tomatoes in your pan, sometimes these splotches will form indicating that the entire bottom of the pan or a portion of it has altered seasoning due to the acidic nature of acid on carbon steel.
  4. Too many thick coats of Flaxseed oil applied during the Flaxseed-oil-method of seasoning could have caused this splotching. Over application of even thin coats of oil could have created the splotches. Usually, though, thick layers of oil applied to the pan will produce a darker in color, almost black. I have noticed that if the coats of oil are not thin, then the pan becomes sticky not just splotchy. By the looks of this pan, I don’t think that there is a high probability of this being the cause.
  5. Putting food in a cold pan might also be a cause of this splotching.
  6. If the pan contained no oil after it was cleaned and dried, this could have been a cause for splotching.
  7. Starting to cook with food in a cold pan is not recommended. Make sure that you heat the pan before putting your food in it.
  8. This splotching could be from regular use.
  9. There could be other possible causes to create this splotchy effect, but does it matter in the long run?
  10. The best thing is to know how to correct the problem and then see if you can avoid what caused it in the first place.

Do You Need to Re-Season this Carbon Steel Pan?

At this point, we do not know if food is sticking to the bottom of the pan. If it is, then I recommend re-seasoning the pan. If the pan is non-stick, then I would continue to use the pan as suggested and see what happens. If the pan straightens out and it cooks beautifully, then leave it alone and use it.

If the pan sticks in some areas and is non-stick in others, then consider re-seasoning the pan.

If you decide to re-season the pan, then it would be a good idea to strip the pan right down to the bare metal and start over with the seasoning process. These carbon steel pans are so tough that you could strip them down multiple times without doing any damage to the pan. You could never do this with one of the “copper-colored” pans or non-stick aluminum pans. Once they are scratched, it is best to throw these types of pans away.

I have posted information here on how to clean and strip your pan. The picture below will show you what your pan should look like after you have stripped it down to the bare metal. The pan below is a de Buyer carbon steel pan and not a Matfer Bourgeat Pan, but the outcome should look similar.

In short, I used 80 grit sandpaper with water. It took some elbow grease, but it turned out great. Do not concern yourself with any scratches that you make. These small scratches will help the seasoning adhere to the pan.

Re-Seasoning Your Carbon Steel Pan

Here is the bottom line. Regardless of what caused this splotching, the important thing is to go ahead and re-season it. You could spend hours on trying to figure out what caused it. Just take your best guess and go ahead and re-season it.

I made a great video on how I season carbon steel pans. Here is the link. I recommend the potato skin, salt, and oil method. Try it.

Carbon Steel Rust

Carbon Steel Rust occurs when your carbon steel pan is not dried and oiled after use.

When you finish cooking with your carbon steel pan, make sure you dry it thoroughly, then apply a light coating of any oil. You can use olive oil, coconut oil, or any oil of your choice. Try not to store your cookware in a humid place like your basement, unless it is dry.

How to clean a Carbon Steel Pan

If your carbon steel cookware is seasoned correctly, then washing it will be a snap.

  1. Never use soap to clean your carbon steel pan.
  2. Never put your carbon steel pan in a dishwasher.
  3. Use a paper towel to wipe the pan as soon as you can.
  4. If food still sticks to the bottom of the pan, put a little water in the pan and dry with a paper towel.
  5. If the food sticking is persistent, then add some kosher salt (it has large grains of salt) to the bottom of the pan and wipe with a damp paper towel.
  6. If this sticking persists, then it might be a good idea to re-season your pan. See link below on how to do that.

How to Re-Season Your Carbon Steel Cookware  Take a look at this link to see the very best way to season your carbon steel cookware.

Additional Questions

Can I remove rust from my carbon steel pan? Yes, rust can be removed from your pan. You will have to sand it down to the metal using 60 or 80 grit sandpaper. When you finish, your pan should look close to new. However, any scratches visible after sanding will not harm your pan. These scratches will help the re-seasoning process.

Do black spots in my carbon steel pan ruin my pan? No. If you pan has rust (usually brown in color) then sand the pan down to the metal as above. Black spots in your pan after seasoning it or using it does not ruin your pan. These spots in the pan could be due to uneven seasoning which is no big deal. Just keep using the pan because it will probably change color many times and this is normal.