Historically bronze was an alloy of copper and tin, usually about 90%&10% respectively, brass was copper and zinc in a 60-40 ratio. Modern metallurgy has developed many specialty copper alloys each with different properties. One can select alloys for such features as machinability, ease of casting, corrosion resistance, heat treatability, ductility, weldability, etc. Unfortunately naming of alloys became inconsistent and confusing so specifying by a standard numbering system became the standard. For example Architectural Bronze and Manganese Bronze both would be considered “brass” based on zinc content alone, while Red Brass has a copper content of 85% which puts it in the same copper percent class as Aluminum Bronze with 86% copper.
Probably, most people think of bronze statues when they hear the word bronze. The most common bronze used in casting art works is Silicone Bronze. The two most common proprietary alloys are Herculoy and Everdur. These alloys contain about 97% copper and are selected for art works for four main reasons, two are due to aesthetics, two are related to workability. When given a high polish silicone bronzes tend to have a slight rosy color undertone that the art world likes. The other is that the very high copper content permits creating a very wide range of decorative patinas that are not possible with more mixed alloys. The silicone bronzes also are easily oxyacetylene welded with matching bronze rod which allows cast components to be assembled into complete works. Also they are easily cold worked which allows for fine detail finishing. None of these qualities are necessary for a drain system and the use of silicone bronze increases the cost by more than three times.
In the early years of IRONSMITH we used the generic “bronze” to cover the description of our copper alloy products. Then, as now, we used C385 Architectural Bronze extrusions for frames and other fabricated items. We used purchased scrap copper and copper alloys obtained from scrap dealers which we mixed ourselves to obtain a suitable cast product. In recent years the availability of scrap copper has dropped to near zero as the value of copper skyrocketed. It is now more profitable for large metal producers to separate scrap and re-alloy it. We then needed to switch to buying bulk alloyed ingot; as such we decided to use the official designation of the alloy we purchase although it is not significantly different from what we used to make.
We have selected these alloys for several reasons; they are mutually compatible, readily available, very suited to the intended use, and the most economic. The customer may have other criteria which are important to them that might require a different alloy. We can provide most any alloy available including silicone bronze but most other alloys are significantly more expensive. We are happy to discuss any client’s specific needs with them to find the most appropriate solution for their situation.