Robert M. Shea
Over forty different fire insurance companies throughout the United States issued cast iron fire marks from 1804 to 1904. These cast iron fire marks are more than insurance collectibles; some are works of art in their own right and representative of 19th century technology. While much has been written about fire insurance and the early insurance companies, very little has been written about the production of the fire marks themselves. It is the purpose of this article to give the reader an understanding of the craftsOver forty different fire insurance companies throughout the United States issued cast iron firemanship involved in their production and, hopefully, a deeper appreciation of the mark itself.
Cast iron fire marks were made by a method called sand casting. In sand casting, a “mold” is made by first mixing moist sand and clay into a moist semi-permanent state. Then a hardwood model of the fire mark, called a “pattern,” is embedded in the moist sand. When the pattern is removed, it leaves a hollow space or void, called a mold, in the shape of the desired mark. The pattern is made slightly larger than the actual fire mark because the molten iron will contract when cooled. Molten iron is poured into the mold and allowed to cool and solidify. To retrieve the finished mark, the mold is broken. Therefore, a new mold must be made for each fire mark.
All fire marks have a “casting mark,” which is the rough area where the molten iron was either poured directly into the mold cavity or flowed, through channels in the sand, into the mold cavity. In casting, the “sprue” refers to the hole and passage through which the molten iron, or “meld,” is poured into the mold. Where the sprue pours directly into the mold cavity, the casting mark on the reverse of the fire mark is called a “sprue mark.” That sprue mark is either a circle, called a “circle mark,” or a thin line, called a “wedge mark.” Where the sprue leads into a channel in the sand and then into the mold cavity, the casting mark on the edge is called a “gate mark.”
The above is a general description of sand casting. The following describes the various methods