Friday, October 26, 2012

Mike Manginella of San Diego writes. You may recall he spoke at the Club’s Symposium last year on cut and engraved glass.

Alan,

So generally I don’t respond to a lot of the great info moving across these pages as I am fairly new to Steuben so I like to just sit back and soak it up. However, Rande Bly makes some interesting notes on Rouge Flambé, and a lot of this has to do with glass in general, something I know a little more about. All the reds that are talked about are glasses starting as a colloidal suspension (if you remember from your chemistry a colloidal suspension is different than a true solution…colloidal is particles that are in solution but can come out). The red is not a color of the glass; it is created by our eyes from the dispersion of light by hitting particles in the glass. This is the same effect as the setting sun. As it goes down on the horizon its light has to travel through more atmosphere and therefore hits and is dispersed in random directions by more particles in the atmosphere. A colloidal suspension in glass is the same. (Another modern use of this is in transition lenses….there the suspension is from silver that when “struck” by ultraviolet rays cause the silver to precipitate out and darken the glass…of course the beauty of these lenses is that when the uv is removed the particles go back in solution and the lens is clear). You have to keep the glass batch in solution by having the melt stay oxidized (more oxygen), then you reheat it (called striking in the glass industry) by putting it in a reducing flame (the reduction means less oxygen). This reduction can happen at the glory hole (the usual method) but also in annealing if the temp is high enough and the glass is in there long enough (FC used this for striking his ruby red into sausages in the lehr). So in the reducing flame the particles come out of solution and then cause the light entering the glass to be scattered and the red is what is thrown out and our eyes pick this up as red. The same principle applies for most reds; gold, selenium, copper, etc. The more particles that come out the darker the red…..meaning darker in the true sense, not brighter. As I understand it, FC liked glass that had depth, so his mixture needed more particles and probably some other ingredients that caused a higher level of opacity in the glass. The lighter orange was by default more transparent (ie had depth but less red) while the rouge was redder but would tend to less transparency (more particles coming out of suspension). The annealing problem could have been caused by too much oxidizing or reducing before entering an annealing lehr that was slightly off from the ideal temp for the mixture…..or from having too many particles come out of suspension (and changing the temperature gradients in the glass itself)….or maybe from another material added to create more opacity (and maybe fighting with other particles in the oxidation and reduction battle). Nonetheless the orange is less particles coming out of suspension so it could happen in areas of a single piece that did not get the same reducing flame as others (think peach blossom, amberina, etc). It also could happen from a slight discrepancy in the mixture itself or from too little of a reducing heat in the final strike area.

Now FC was a true master of glass, and his knowledge was pretty much state of the art, so my feeling is the Rouge Flambé was this dogged attempt to get this mixture to be both a perfect (for FC) level of transparency (depth) and a perfect (in his mind) color of red. Not sure if anyone is interested, but I love reading this stuff and putting in my two cents. Of course this could be all “tommy rot” and FC would be all over my case (now that would be something to be cherished).

Thanks

Mike

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2013 Carder Steuben Club annual Symposium will be held at The Corning Museum of Glass in Corning, NY from September 19-21, 2013. The festivities will begin with Frederick Carder’s 150th birthday celebration on the evening of September 18, 2013.