Molten glass and viscosity question

nikchristensen

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Jan 29, 2017
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Thanks for reading,
I'm a glassblower trying to make sense of logarithmic graphs depicting the viscosity of glass at various temperatures. An example is attached and linked to below but more can be found by just googling "glass viscosity and temperature."

https://www.researchgate.net/figure/278780386_fig1_Fig-1-Comparison-of-the-viscosity-of-several-kinds-of-glass-versus-temperature-Some


My interest is in "soda-lime" glass specifically (there are different viscosity curves for different glass compositions) and with these graphs you'll find that the glass is considered to begin moving only when the poise drops to log 7.6. As the temperature increases, the glass moves more fluidly through a "working range" and then is considered to be too hot to manipulate at poise values much below log 4 (log 3 certainly).

I'd love some assistance with analyzing this relationship! Here's my main questions:

1. In these graphs, the curved line seems to bend sharply (from more being more vertical to horizontal) within this range... does (along with the fact that it's a logarithmic relationship) this indicate that the increase in fluidity of the glass is not uniform, but rather increases dynamically as the temperature rises?

2. How much more fluid is the glass between the softening point and the working temperature (between log 7.6 and log 4)? In terms of orders of magnitude, I guess... Is it like 10,000 times less viscous at the higher temperature?

Thanks in advance for your responses,
Nik
viscosity.jpgGlassviscosityexamples.jpgViscosity-Temp Curve_300px (1).jpg
 
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