#COBALT CHLORIDE WEATHER INDICATOR WINDOWS#

For example, a recipe would suggest dipping an alum-written letter in water, where the writing would turn from white to black or it might advise rubbing powder on fig-tree milk to make it visible. These books occasionally included directions for creating invisible ink, written as a basic kitchen recipe using simple and readily available ingredients. The 16th century was the heyday of “books of secrets,” compilations of technical and medicinal recipes and magic formulas. Although silver brought riches to the town, cobalt produced many more exotic marvels including invisible ink. Streets such as Silver Road and Cobalt Road still snake through the Schneeberg landscape and define its past. Miners removed hundreds of thousands of kilograms of cobalt from the mountain. Until the 16th century, Schneeberg was known as a a silver-mining town, but after workers depleted the known veins of that metal they turned their attention to cobalt, which was in high demand for coloring glass and other goods.

Located in the Saxon Ore mountain range, the Schneeberg Mountains once contained rich sources of silver, bismuth, and cobalt hidden beneath the bucolic exterior of verdant hills and valleys. It is easy to imagine the music of Bach wafting through the cobblestone streets of this Baroque village. Villagers there still use the miners’ greeting Glück auf!-Godspeed-and the hammer and pick symbol still decorates knickknacks, buildings, walls, and fences.

#COBALT CHLORIDE WEATHER INDICATOR WINDOWS#

I have fond memories of hiking up and down the trails surrounding that mountaintop village, where shop windows are filled with hand-carved nutcrackers, smoking men, candelabras, angels, and pyramids. That is why I was excited when, a few years ago, I had the opportunity to visit Schneeberg, Germany (below), one of the birthplaces of these magical substances, and a rich source of inspiration for modem chemistry. I’ve been fascinated by the history of invisible ink for a number of years, and have even worked with my colleague Jason Lye, a color chemistry expert, to re-create some traditional ink formulas. But other historical and cultural circumstances carried the inks to 20th century America, and ultimately into modem popular culture. It was a heady time, an era when popular science became intoxicating low-tech entertainment in a low-key world. It was against the backdrop of this witches’ brew of circumstances that invisible ink flourished. During that era of intellectual ferment, a rise of stage magic coincided with a revival of so-called natural magic-an occult tradition that sought power from natural sources, such as herbology and astrology-alongside an increased demand for public scientific demonstrations.

The tale begins with tire discovery of a magical appearing and disappearing ink, and crests with a convergence of trends during the end of the Enlightenment in the 18th century.

Cobalt chloride weather indicator