Came Types

     Lead Came: Lead is a soft malleable metal (it can be scratched with 
a fingernail). It naturally produces a protective dark bluish-gray patina. In 
the mid-19th century, improved smelting processes enabled manufacturers to 
extract valuable metal impurities from lead, thereby producing 100% pure lead 
came. The industry reasoned that 100% pure lead came was superior to the less 
pure variety. Although pure lead came is very workable and contributes to 
intricate designs, time has proven it to be less durable than medieval came, 
which contained trace elements of tin, copper, silver, and antimony. 
Unfortunately, the misconception that pure lead had greater longevity continued 
throughout the glory years of leaded glass use in America. Most glass 
conservators use a 100-year rule of thumb for the life expectancy of 19th 
century came-less for came produced during war times. The demand for lead 
ammunition and the resulting scarcity of lead required studios to stretch the 
available lead to its limits, thus resulting in weaker cames. In the 1970s 
"restoration lead" (ASTM B29-84) was developed based on metallurgic analyses of 
medieval cames, some of which have lasted for centuries. Restoration lead should 
always be used when releading historic windows.

     Zinc Came: Zinc came is more vulnerable to atmospheric corrosion 
(particularly from sulfuric acids) than lead, but has proven to be durable in 
America because it weighs 40% less than lead and its coefficient of expansion is 
7% lower. Thus, it is somewhat less susceptible to fatigue from expansion and 
contraction. Moreover, it is ten times harder than lead, and has three times the 
tensile strength. Zinc came is strong enough to be self-supporting and requires 
little bracing to interrupt the window's design. While zinc came is perfect for 
the geometric designs of Prairie School windows, it is usually too stiff to 
employ in very curvilinear designs. Zinc can also take several finishes, 
including a copper or black finish. (As a result, zinc can be mistaken for 
copper or brass.)

     Other Came: Other metals, primarily solid brass and copper, were 
also occasionally employed as came. They are generally found only in windows 
between ca. 1890 and ca. 1920.