Why Does Food Turn Black In A Cast Iron Pot?

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Remember the rusted cast iron Kadhai we re-seasoned and made as good as new? It was from my mom’s place. She had ditched it because the food cooked in it was turning black in colour. So, she kept it away in the storeroom till I rescued it on my last visit.

Food turning black is a common problem that cast-iron novices face. Though it doesn’t affect the quality of the food, the black colour can be unsightly to many. The cause? Either because the iron cookware isn’t seasoned well enough or because of burnt food residues. Let us explore both in detail and see how to prevent them.

Cause 1: Cast Iron Not Seasoned Properly

Cast iron, as you know is an alloy of iron, carbon and silica. It is poured into moulds of different shapes to make various cookware. It is then shot blasted to remove all the grit and dirt it may accumulate in the manufacturing process. Finally, it is oiled and heated in the kiln for seasoning.

Unseasoned or poorly seasoned cast iron cookware has carbon residue on its surface. When you cook food in such cookware, the carbon residue may transfer to the food and impart a black colour to it. You can check if this is the cause by wiping the cast iron with a slightly oiled cotton cloth. The cloth will have a brownish-black stain on it.

why food turns black in cast iron cookware
Carbon residue on unseasoned cast iron cookware

Yet another reason is that compared to well-seasoned pans, poorly seasoned cookware transfers a higher quantity of iron to the food. Just like how your teeth get stained and your poop turns blackish when taking iron supplements, your food too turns black when left in cast iron cookware due to the unabsorbed iron in it. This happens especially so when you leave the food in the cast iron pot for long.

Related reading: Common Cast Iron Problems and Their Solutions

So, if your food turns blackish in a new cast iron cookware, you needn’t worry at all. In fact, it could even be considered as a positive because it means your food is now highly fortified with iron.

If you want the food to stop turning black, season your cookware once again. For this, apply a coat of vegetable oil all over the cookware and wipe off the excess with a cloth or paper towel. Then, heat it in the oven at 200C for 30-45 minutes or on the stovetop till the oil starts smoking. Also, avoid storing food in cast iron cookware, especially when it is new.

Related reading: How To Clean Cast Iron Cookware

Cause 2: Burnt Residues

Some people don’t clean their cast iron cookware with soap fearing its seasoning may wear off. This however is a myth that has long been debunked.

Over a period of time, burnt food residues will get stuck in the pores and crevices. This could get transferred to the food, thus imparting a blackish colour to the food.

To resolve this, clean your cookware using regular dishwashing soap and a non-abrasive scrub. The seasoning on cast iron is polymerised oil that is bonded to the iron. It doesn’t get affected by soap. Only scrubbing with an abrasive brush or heating to an extremely high temperature can wear it off.

Related reading: Best Dosa Tawa in India ( Cast Iron and Nonstick)


Well-seasoned cast-iron cookware will never turn the food black as the seasoning regulates the iron transfer rate. So, even if your food turns black, season it and keep using the cast iron cookware so that over a period of time, it develops a thick layer of seasoning giving fancy enamelled cast iron cookware a run for their money!

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1 thought on “Why Does Food Turn Black In A Cast Iron Pot?”

  1. We knew it long time ago when my mother used to use iron utensils. We try to buy and use these utensils thanks for the knowledge.

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