Phosphorus, Oolitic deposits, and Chinese Made Cast Iron Cookware
Cast iron is a great way to make cookware. It’s cheap and can easily be cast into complex shapes. It’s safe too; if you ground a cast iron pan into a fine powder, you could safely eat it over the course of 18 months.
This simplicity heightens the importance of the quality of the cast iron. Cast iron is mostly iron, followed by 2-4% carbon. Higher carbon makes it harder and gives it a lower melting point, while lower carbon makes it more ductile. There are also impurities in cast iron; notably phosphorus. Phosphorus generally makes cast iron more brittle when exposed to rapid temperature changes or on impact, and while a little can be good during casting it’s considered an impurity. As little as 0.1% can make it more brittle.
What’s important is different mines have different concentrations of phosphorus and other impurities. Chinese mines often have higher concentrations of phosphate minerals than the US, largely due to the types of deposits found in each country. While much of Asia (including China, India, and Kazakhstan) have more oolitic deposits, countries like the US, Brazil, and Australia tend to have hematite and goethite deposits. Oolitic deposits contain more phosphorus, and may produce a more brittle cast iron product.
To make the argument even more compelling, Chinese pans are not meaningfully cheaper than American made pans. Lodge, the largest manufacturer of cast iron cookware in the US, sells $20 10.5-inch pans , which is about the same price you’d pay for a Chinese made pan. Since the US produces so much iron, and the iron which is imported usually comes from countries like Brazil and Canada, it's reasonable to think you're getting a higher quality iron for a similar price just by buying American made cookware. Even if your pan is made from scrap iron and steel (which is not uncommon), that scrap metal is more likely to have started life as a higher quality steel if it is sourced from the USA.
