20 June 2006

Berg’s Project: Presentation of Experimental Information

The information Berg presents in each experiment is consistent throughout the six notebooks. Each begins with a list of ingredients and the quantities used. The substances and combinations varied widely, but for most experiments Berg used fewer than seven ounces of ingredients in total. Typically, a sentence or phrase giving the place of firing and length of time in the furnace or kiln followed the listing of ingredients. Berg often used the furnace at Stephen Hall’s Falcon glass works or at Whitefriars’, identified as [Cary] “Stafford’s furnace” or the jeweler’s kiln identified as “Carter’s,” probably that of Edward Carter. Firing times varied from a half-hour for some enamel colors to a full day or longer. Berg’s records continue with one or two sentences about the result: appearance, consistency, weight, whether it could be worked and if so how well, and so forth. Important to our recognition of Berg’s understanding of chemistry is his inclusion of a chemistry-based explanation or mechanism for his finding.Controlling the quantity of phlogiston and balancing the affinities of ingredients are two concerns we would expect to find in a practical work about eighteenth-century colormaking: Berg’s concerns with both is irregularly expressed in his notes. His comments also recorded such failures as mixtures that ran over or could not be extracted from the crucible. And finally, Berg added comments to some experiments weeks or months later. These remarks might note that a formula effloresced, fell apart, or perhaps was given to a glassblower to make a small bottle or other trinket.


At 06 July, 2006, Blogger Sarah Lowengard said...

About This Image
Experiment 96 is the first experiment in Notebook 2, dated 11 Noember [1762].

I am a willful ignoramus about all things photographic, and so it is a difficult image to read. This is what it says:

¾ oz sand, 1 oz and ¼ of nitre, ¼ oz of putty, ¼ oz of minium with 2 drams of borax One hour in fusion produces a very white opake mass much better vitrified & more fritt for my purpose than the former Ex: thus I find this small addition of borax has had great effect in the vitrification, it seems to want a little more Borax as there were several little holes or Cells in the composition which a little more Borax would remove or else a little stroner fire. There was a blackish scurf at top. This composition did not hiss when hot which hissing I attribute to the mixture having some Arsenic among it.
N.B. In the preceeding Ex: the Aresnic in the composition makes the Nitre when the crucible gets hot make a great hissing noise for some time & I suppose great part of the Nitre is dissipated as it looses much of its quality as a flux but with Borax instead of Arsenic that difficulty is removed.

The comments continue on the following page: I believe the blackness at the Top of the Composition Ex: 96 is occasioned as follows the Borax extricates the Marine Acid from the Nitre which is thrown to the surface and there remains as being uncapable of vitrifying.


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