jfcutter
Posts: 71
Joined: 10/27/2004 From: Klamath Falls, OR. Status: offline
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Hi "bostaurus" and you are right about the Historic Bottle Website not including any real information on "flashing." It just wasn't something done at all with common, utilitarian bottles so I haven't covered it at all, although I should at least add some mention of it to the Glossary page. It wasn't too uncommon with what I call "specialty" bottles like the two example you note. According to my Handbook of Glass Manufacture (Tooley 1953), other terms for flashing (which was a glassmaker term also) were "striking" and "cased glass"...your noted term "casing" for short on the last one I guess. The definition of cased glass is "glassware whose surface layer has different composition from that of the main glass body." Flashing is "applying a thin layer of opague or colored glass to the surface of clear glass, or vice versa. See also striking." Although this doesn't say how the glass is applied but is what the proper term for your items is. Striking is defined as "development of color or opacity during cooling or reheating." This is different than applying glass but points out that glass colors are influenced by more than just the chemical composition of the batch itself. I remember Toulouse noting that a regular batch of bottle ("green") glass could be made very blue (deep blue green) or true green to aqua green during the same day by having a "reducing flame" or an "oxidizing flame." This could result in the early morning items (after a night of banking the fire under the pot with the air vents shut down) being very blue in color with those as the day proceeded being green (or aqua) blown from the same batch of glass! That explains some of the wide ranging variety of bottle colors (like the array of blue to blue-green to green Henley's IXL Bitters out West here) and the fact that they didn't have to be blown from different batches of glass, but could have been blown on the same day from the same batch of glass. Sorry, I digressed there...unfortunately, Tooley's great book noted above doesn't tell how to do flashing except as implied by the definition - that a thin layer of glass is applied...dipping being the most likely it seems, as you noted. However, Frank Kulasiewicz's book "Glassblowing - The Technique of Free-Blown Glass" (and excellent book BTW) does include a description of the process of "Striking or flashing a colored glass..." (page 143). In short, it is a "chemical reaction in molten glass that leads to the formation of particles of colloidal size precipitating out of the saturated glass." Now what does that mean? It appears that the striking method of flashing is done more by various heat treatments to specific chemically composed glasses, not dipping (although I think that can be done to?). More specifically, "..the striking process is complicated and often depends on special heat treatments to start the crystallization process and special chemicals to reduce the metal out of the melt or to act as the nuclei for growth." He, at the end, makes reference to it being a "art" and hard to describe in that "...complicated theories have been published, yet these do not dispel the magic of clear glass suddenly becoming colored." Sorry for the long response here but wanted to figure it out for myself so that I can add something to my Glossary page about the subject. I already cover "flashing" very briefly there, but need to expand it a bit to cover the "striking" possibility. So I guess the bottom line is that it could be applied glass (how, isn't specified) or done through the striking process vaguely outlined in "Glassblowing...". Glass is such an interesting substance, eh?
< Message edited by jfcutter -- 4/17/2009 9:46:03 AM >
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Bill Lindsey - Klamath Falls, OR. Author of the BLM/SHA's "Historic Glass Bottle Identification & Information Website" http://www.sha.org/bottle/index.htm (...and a collector of American mouth-blown bottles)
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