View Single Post
Old 03-31-2005, 12:08 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,034
Pete VanderLaan is on a distinguished road
Re: Re: AP

Originally posted by Lani McGregor

I'd wager that any colored glasses that fit that base clear (i.e. show little stress in a ring, pull, Trident seal or BE chip/bar test) but have a much lower AP (such as a lead glass would) will NOT have a 94-95 COE. Their measured LEC (0-300C) will be lower.
The spreadsheet I run brings SP87 in at a 94.6 and measures with dilatometry as a 95.9. When I use that spreadsheet on fluorine glasses at 6-7 percent, I bring in a calculated expansion of 72.3 and they almost always fit the first time. I do not know the assumptions in the program being made about the fluorine that makes this so low. They also measure 95.9-96.0. It is also the case that a pulled thread of those glasses has a serious arc. I am no where near the program right now so I cannot say about the annealing Log.

I do know that opal lead fluorides from kugler have ( or at least had the last time I tested) an expansion coefficient of about 89 . They however do not fit SP87 at all. It is why Tom created SP83 which I always thought had a measured L.E.C. of about 90.5 That would be within the 1.5 ten thousandths tolerance that has been accepted in the past as the maximum outside tolerance for expansion coefficient fit. .

I am confused though about the viscosity issue. Any Kugler rod will really run on the surface of a piece made with most commercial clear glasses indicating a lower viscosity than the host clear. This could be , either cullets or batches. One of the main reasons people really liked my black as an example was firstly the density of the color but also the fact that it does not bleed at all and stays absolutely where you put it. . It measures a 96.0 but has a close viscosity match to SP87 and still contains a substantial amount of lead.. It presents no strain in a ring test at all. I find bringing all of the gut features of a glass body to be very contradictory especially when one is trying to match up radically different formulations. I am thinking out loud here and will probably get an earful from someone.
Reply With Quote