i've noticed more and more cold-rolled steel or iron porcelain enameled advertising signs being dug from both commercial and residential excavation sites across chicago over the past few months. nearly all of the signs unearthed are heavily corroded with the polychromed enameled finish faded, but intact enough to identify the product or service and approximate date the sign was fabricated. the burdick enamel sign company was one of chicago's earliest sign makers that manufactured both "stock" and customized porcelain enameled signage.
vitreous or "porcelain enameled" exterior building advertising signs first appeared during the late 19th century, where they were being imported from germany and other European countries. these robust, weather-resistant signs were made from heavy gauge cold-rolled iron and die cut into customized shapes and sizes. the visually striking colors, lettering, and graphics were achieved by fusing powdered glass against iron by firing at extremely high temperatures, whereby the powder melts, flows, and eventually hardens into a smooth durable vitreous coating.
the incredibly durable finish is the primary reason why i'm discovering signs at dig sites across the city of chicago. whether they are being unearthed from long forgotten dump sites or dug behind commercial buildings these early 20th century american advertising signs have withstood the test of time. identifying and documenting signs is not only a useful dating mechanism, but greatly helps in shedding light on businesses long forgotten, or perhaps a product popular during a given time period.