Those blog posts are great - thank you!
After reading the final post, though, I want to be sure I understand the relationship between COE and viscosity.
She tells the story of the blue and purple streaky glass that combined an opal and a transparent, and kept breaking. Matching the COEs didn’t stop the breakage; making the COE of the opal lower did. But she doesn’t explain why that was the case.
In comments, she says that viscosity is more important than COE for compatibility. She never specifically explains how viscosity figured into solving the streaky glass problem, but I infer that making the COE of the opal lower adjusted its viscosity in such a way that the two glasses were then compatible. Is that correct?
She says in comments, “Our experience indicates that you can be off by as much as 10% in expansion difference, but not more than 5% in viscosity.”
In the videos about drop rings - the point is made that differences in viscosity will cause glass of one type or color to drop more rapidly than another. But, since they are all “Bullseye compatible”, does that mean a difference of less than 5% in viscosity would still cause a big difference in how fast the glass drops?