20 June 2006

George Berg’s Experiment Book: The Contents of the Experiment Book

The experiment book’s contents provide a variety of insights into Berg’s glass and chemistry activities. By tracing the ingredients and techniques included in the experiments, we can identify the kinds of glass Berg hoped to make or to improve. We can compare Berg’s comments about results with his subsequent experiments, to understand what he hoped to accomplish with the changes to his formulas. Within certain experiments such additions as a calculation of proportional gravity of the glass or explanations of results—sometimes entered days or weeks later—further indicate how Berg incorporated ideas about the chemical combination of matter into his work. Notes about discussions and lectures offer insight into Berg’s understanding of the problems inherent in reaching his goal, and the routes he chose to improve his comprehension and results.

Our examination of the information George Berg recorded in his experiments leads to several conclusions about the purpose of his project. First, combined with the notes at the back of the first two notebooks and similar comments in the remaining books and on the inserted papers, the experiments confirm that Berg was learning and using contemporary chemistry to improve his understanding of glass formulas. At the same time, he was creating these formulas for two very specific outcomes. He made gem-like glasses, either for the carved or molded “cameos and intaglios” that imitated antique stones or for the more prosaic false stones set into buckles, jewelry, picture frames, or other small metal wares. Berg also made colored glasses that could be reground and used to color enameled wares, probably small boxes, or other trinkets.


At 12 July, 2006, Anonymous Anonymous said...

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At 14 July, 2006, Blogger Sarah Lowengard said...

Proportional Gravity
For Berg, proportional gravity was the ratio of the weight of an object in air to its weight in water. He calculates this number for several of his formulas, and it seems (to me) to be related to an observation of Edward Hussey Delaval, that “ Denser substances ought, by their greater reflective power, in like circumstances, to reflect the less refrangible rays, and that substances of less density should reflect rays proportionably more refrangible and thereby appear of several colours in the order of their density.” (page 12 of paper cited in n.11 below). Delaval noted the following correlation:
Gold produces red colors,
Lead – orange
Silver – yellow
Copper – green
Iron – blue

In 1777, Delaval read another paper at the Royal Society, in which he refuted most of the conclusions in this earlier (1765) work.

At 14 July, 2006, Blogger Sarah Lowengard said...

Some Internet-based Resources about 18th Century Chemistry
Historians who write about 18th century chemistry tend to carve it into smaller pieces and off-hand I can’t think of a single online work that succinctly discuses all aspects of chemistry in the 18th century West. (Please tell me if you can.) Some university websites give the public access to course webpages but these may appear and disappear by semester. Here are some more stable websites that do have information:
Carmen Giunta’s Classic Chemistry Website http://web.lemoyne.edu/~giunta/index.html. The site includes a page of links to other sites about the history of chemistry
The Alchemy Web Site www.levity.com/alchemy
Hyle, An International Journal of the Philosophy of Chemistry http://www.hyle.org/journal/search.htm


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