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Old 03-31-2005, 10:49 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 21,956
Pete VanderLaan is on a distinguished road
Durk: I understand what you are saying but my understanding of the story is somewhat different in that Klaus got tagged with an overhead photograaph showing clearly a cone emanating from the shop that literally showed death and destuction of vegetation that focused in his yard.

The thing that bothers me about what you say is the incredible variation in L.E.C. in the stick and my best understanding is that it persists to this day. I specifically refer to the soda lime based sticks of bright yellows and red opaques which the last time I measured them were actually about an 85. This would be a group of rod that virtually fits nothing and I have to question why it would be produced if it could actually be controlled. Since most of the lead flourides run around an 89 and the transparants a 94-94.5, what is the possible motivation in not at least standardizing the L.E.C.'s when it is not difficult to do. Lining up the viscosities is another and more substantial problem ( tip of the hat to Lani here)? So my assertion that they have been- at least in the past, stuck with a premixed leaded batch that they added colorants to and that explained the wandering L.E.C.'s I would assume that the lead fluoride batch is a different base formula but I don't know that and the soda lime base for the cadmium selenium glasses has to be a diferent formula. The formula for the lead arsenates could be a simple addition of Arsenic, but I doubt it.

But making glasses that fit nothing continues to baffle me.

Lani, I understand what you are saying and understand the point to which you refer but I do normally look at the range in which annealing can and does take place at varing speeds. We certainly also agree that thickness changes everything. I would note that the 918 falls exactly in the middle of what I suggested the range to be. Once we get out in the field, we find that the equipment is a hell of a lot looser than we would like to see it be while at the same time, the opinions about what is wrong today are wide, varied and unsubstantiated. Even while you refer to the annealing point as 918, I am almost positive that Tom has referrenced 895 as an annealing point at some time in the not too distant past. I assume that would be the lower point.

With my own work on the cut glass pieces- and you saw one when I was up in Portland in 2003, those pieces cannot go into a lehr at 940, let alone 918. I need to put them in at 995 for about an hour and then to lower them slowly to 945 or they simply crack when I do the knife edged grinding that they require.. That says to me that there is something going on in annealing land which I cannot account for except empirically. I trust my controllers and thermocouples.

Dilatometry was also approached back in the '80's by Steve Maslach as well who did a GAS presentation on it as well. I did not ever see the presentation but I did read about it and Steve was really jumping thru hoops to make sure the sample didn't drag on the side of the sample tube. When I asked him about the presentation, he didn't want to talk about it. Now, I have never had any of those problems. I do not think the dilatometer is a holy grail at all. still really only trust the ring test as a final arbiter but the dilatometer gets me right into the ballpark and tells me if I am high or low. If the ring test, or the trident seal is off by much, the sample doesn't survive the test and the information is fairly useless. The trident seal is way more sensitive to self destructing than the ring is which is why I prefer the ring.

I think that Steve O'Day is correct about Theresa at C R LOO being the first to make comparison charts which told everyone about the expansion factor of each glass. I think that really came out as the number of players in the sales field expanded exponentially in the late '80's and a lot of people were just randomly throwing colors together and then happily blaming the vendors when things cracked ( what else is new?).

To simplify for me I have to say that the rules for fit are simply different in blown, cast and slumped ware. People do such bizarre things with the product that creating a homogenous rule of thumb leads me down the path of madness.
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