The Chemistry

The formula used to make thin cast iron in the last century is very different from what is used now in modern machine casting facilities.

There was a time in the 1800s when iron was Apple.

In the settled areas of the United States in the nineteenth century foundries were everywhere.  Foundries were everywhere because iron implements were everywhere; plows, and pulleys and steam boilers, building facades were made from cast iron, and even extremely thin jewelry. 

Iron was king and everyone wanted it.

Today, cast iron cookware from some of those nineteenth century foundries, the high grade extra-finished hollow ware, have an almost mythical reputation. They ARE incredibly thin and smooth, and their performance is unmatched by today's conventional machine-made cast iron.

We’ve reconditioned hundreds of pieces of vintage and historic cookware and we certainly thought we knew something about how they were made. But in 2013 when I set out to make cast iron cookware just as thin and smooth as those historic pieces the exact chemical formula for the iron was a mystery. 

Informed people would say “They used purer iron to make those old pans”.

Some people believe that in the 1900s the purer veins of ore somehow contributed to the smoothness of the old cookware. We did spectrographic tests on some of our own historic pans to analyze the chemical contents and they aren’t pure at all. If fact, by today’s standards they contain much larger percentages of trace elements. 

Foundrymen would tell me that the fine finish and thin walls had nothing to do with their casting technology, it was all old fashioned handwork…again, BS.

It was as though many of these new foundrymen had forgotten their past. They certainly had forgotten how the best of the old cookware was made. And it wasn’t by hand, not in the way we think of “handmade” today.  These were large manufacturing facilities at the beginning of American industrialization. The Favorite Stove and Range Company in Piqua Ohio, one of the finest manufacturers of stoves and cookware, occupied an eight-acre site and employed 316 men in 1916.

The polishing was done on large machines not by hand.

"Handwork" had little to do with the quality of the old cookware.  

The recipe changed.

Those old thin-wall pans were not cast with purer iron, nor were they polished by hand, but they were made with a different recipe...sort of like the difference between a homemade sourdough starter bread and a quick rise recipe for industrial yeast-made bread-totally different recipes for totally different processes.

The foundry engineers of the great cookware manufacturers of the last century; Griswold, Favorite Stove and Range, Wapak Hollow Ware Co. were very careful with their chemistry. I’ve seen their records. Their recipes contain element percentages down to the hundredths. They engineered their formulas precisely for the necessities of pouring thin-wall castings with very fine face sands.

Where does the Butter Pat iron formula come from?

We were frustrated. We needed a formula to meet the critical requirements of our thin-wall specifications. The foundry engineers we worked with didn't have the right mixture.  We met with metallurgists and worked with the FIRE foundry program at Virginia Tech. We ran casting simulations to check the freeze rates of grey iron in the thin wall sections.  We consulted foundries and engineers around the country but no one was pouring iron this thin.

I’m sure we could have figured out the formula eventually; the chemistry was all there, if not the practical applications-but the exact formula was illusive.

We found the old cookbooks.

We’re friends with a couple who arguably have the largest collection of cast iron in the world. It is a fascinating assembly of all types of skillets, cook stoves, waffle irons, trivets and foundry memorabilia. Any visit with them is an insight into the preeminence of cast iron in American history.  

In 2014 I spent a number of days reviewing the engineering notebooks that make up part of their collection. It was there, in an old ragged book, that I found the formula for thin hollow-ware; the portions were exact and distinctly different from those we'd been testing.

It is largely this formula we use today.

When we took the recipe back to the foundry lab our metallurgist said “so that was how they got it to flow so thin and smooth!”  Not handwork.  Not purer iron.  No, the engineers at those old foundries knew the science. They engineered the formula.

With minor tweaks, the formula we found in the old foundry records is the recipe we use in Butter Pat cookware.