Kelly started experimenting with his "air-boiling process," a process of blowing air up through molten iron to reduce the carbon content, in the 1850s. His initial goal was to reduce the amount of fuel required for iron and steel making, because of the immense amount of timber required to make the charcoal. He discovered that the injected air did not cool the molten iron, but instead combined with the carbon to cause the iron to boil and burn violently until the carbon was greatly reduced, improving the quality of the iron or converting it to steel. His iron workers may have contributed to his discovery. According to Kelly's biography, in 1854 he hired Chinese iron workers through a New York teahouse. Historian of metallurgy Donald Wagner notes that a similar process was already extant in China, and that Kelly's Chinese iron workers were likely familiar with how molten cast iron behaved under an air blast. The engineer William Phillips, after a trip to Eddyville, wrote in 1899 that "the Chinese had refined iron by blowing air into it a great many years ago, and I have thought that Kelly, in asking for Chinese laborers, would naturally require the services of those who had some knowledge of the iron business."