View Single Post
Old 02-18-2020, 05:31 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,120
Pete VanderLaan is on a distinguished road
When Nick Labino initially wrote the formula for SP, it was a good deal higher percentage than what was finally settled on. I recall it as SP92. The issue was the lithium content and it was dissolving the furnace so, Nick cut it back to where it is today for the SP87. There are other SP formulations but are not commonly in use but they do fit Kugler's opaques which were lower in expansion. Those Kuglers did not then, and do not now fit the standard issue of SP87. It was , I believe marketed as SP83.

Lithium is a profound flux. John Croucher identified, through Appen I recall that the expansion factor should in reality be 4.92, a big jump from the 2. whatever it had been at. Glassnotes IV did take note of that change in that edition at my urging .

Bottom line is that it's a two edged Sword. Since I have no idea which formulation Charlie was in search of at the time he decided to go to melt in the Czech Republic. it's a very tricky material to dance with. Also, it's really expensive. The last time I bought it, it was over $500.00 a fifty lb bag and it had gone up a good deal since then.

What I'm sifting through right now as to cords does sound like a lithium influence. It will eat a furnace alive if excessive. The stuff Eben refers to is not material that can be evaluated at this point.

In my mind, SP87 is the reliable material of choice.
Where are we going and why am I in this basket?
Reply With Quote