Prior to sometime in the early years of the 1900's - and still to some extent up through WWII - there was a master craftsman (I don't recall the technical name) in charge of running the smelting of iron ore into metal. How each one did it was a complete secret that each guarded carefully. The only way to figure some of their formulas out is to do extensive metallographic research, and even that has it's limits to know what they did.Photog200 wrote: I have no doubts there is something in the formulas that each foundry used in their stove that made stoves last longer. I wish there was some records of the formulas used so would could find out what the difference was. I would suspect, those formulas were closely guarded secrets.
Randy
Bog iron deposits varied from site to site depending upon what the local geology was. However, bog iron did tend to have very few impurities, especially missing were sulfur and phosphorous - two elements that have to be tightly controlled for metallurgical reasons. Silicon in cast irons is needed up to a certain point as it provides what is called fluidity. That is the ability for the molten metal to flow inside molds well, fill them and not leave cold shunts and other casting defects.
One of the famous bog iron sites is found in Japan, which I understand is still used today in the artisan production of Samurai swords (considered a national treasure). It is that bog iron, which is credited as being one of the purest iron ores in the world, that is used to produce the Samurai sword. One of the multiple reasons for the excellent quality of those swords was the use of that bog iron during original smelting. This is a long subject unto itself...
Once you are getting cast irons made in the early 1900's and beyond, those are beginning to become quite high quality cast irons - if the manufacturer wanted to make them as such. All nostalgia aside, the quality of cast irons today are greatly superior to cast irons prior to 1900, and between then and WWII, also most likely the case. There are some cast irons during that time period that could approach what we can do today.
Cast irons are not like the bronzes. The Chinese had perfected the cast bronze technology in ancient times. That technology has been lost. We still cannot today reproduce what they had achieved. That is not the case for cast irons.
dj