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Franklin Sankar 04-10-2019 09:28 PM

Why that working temperature
I started to reduce the furnace temperature gradually over the last year because felt that if the melted glass was still viscous at the lower temperatures that was ok. Then I forgot I reduced the temperature and started to get all kinds of problems.
So the question is how did you choose the working temperature for your furnace.
I noticed some people would have one temp and others another.


Pete VanderLaan 04-11-2019 08:16 AM

you tool up for what you are making.

Eben Horton 04-11-2019 09:38 AM

The hotter the glass the smaller your gathers. The colder the glass the bigger the gathers can be but it comes at a cost of working time and the possibility of bubbles forming from your gather tails folding over them selves.

I usually keep my furnace at 1970 when I am working. The defecto working temp at most schools and public access studios is 2100 which I think is too hot for production.

Shawn Everette 04-11-2019 10:11 AM

I agree with Eben, it's more a matter of preference. I keep mine about 2100 in general, but I actually like doing my production session after a fresh charge while it's still piping hot. I like sloppy bits that need no reheat.

What you are actually batching is going to have a pretty drastic change on ideal fining and working temp.

You can gauge temp with either a controller or pyrometer, or go old school and tell by color. You'll get the eye for color eventually either way.

Art Freas 04-11-2019 08:10 PM

We are working with the Cristalica and initially we tried 2100 but it was just too thick to get the gathers we wanted. It was hard to get the right amount to work thin without taking a lot off the pipe. We now work at 2125.

Franklin Sankar 04-11-2019 09:08 PM

My Wire elements won’t like 2100. It is interesting that 25 deg. makes such a difference in gathering.

Shawn Everette 04-11-2019 09:12 PM

You need new elements

Bob Meyer 04-11-2019 09:28 PM

This might be a good time to mention the variation in temperature readings between different furnaces and thermocouples.

Pete VanderLaan 04-12-2019 08:51 AM


Originally Posted by Art Freas (Post 143628)
We are working with the Cristalica and initially we tried 2100 but it was just too thick to get the gathers we wanted. It was hard to get the right amount to work thin without taking a lot off the pipe. We now work at 2125.

That's what I meant when I said you tool up for what you are making. Efficiency keeps you from being exhausted. Sometimes you can turn it down, sometimes up. That's far more flexible than most tooling in the shop.

Shawn Everette 04-12-2019 09:01 AM

Color and viscosity are king.

Pete VanderLaan 04-12-2019 09:44 AM

In terms of flash, yes.
When I consider things I have read at other sites, I see a lot of speculation on things like expansion where no basis for the speculation exists. Or, solutions based on something bizarre. I always like to remember Heidi Broderbund's 15% rule on compatibility ( don't use more than 15 percent of a known bad glass in your work and you'll be fine), or "You can put the purple over the blue but not the blue over the purple".

I don't put up with that kind of junk theory here and given the teaching these days, you aren't going to get the real deal from your instructor. Now that Henry's book is out of print, there really is no bible one can go to, so flat earth theories abound. I see it on clear cullet all the time. Relying on the manufacturer is simply not a good idea, the distributor either.
If you don't have copies of Glassnotes 3 and 4, buy them wherever you can find them. Those will become scarce books. Actually, they already are.

Shawn Everette 04-12-2019 10:11 AM

I've always been able to glance at a tank and know somethings up before I look at the thermo readout, even if it's 50 degrees off. Know the glow.

I've gotten away with some questionable stuff at times, but I'd never make a rule of it. Or try to convince someone that it was other than a fluke. That 15% rule probably originates in the moretti crowd, you still see it posted on torch supply sites.

Watching Fero put everythig under the sun but boro on one of his birds, then put it on the table when he was done, was kind of an eyeopener. Doesn't mean I'm gonna try it.

I just saw what Glassnotes 4 was going for, putting mine in a safe.

Pete VanderLaan 04-12-2019 10:48 AM

Halem-Glassnotes 3 and 4
Weyl- in whatever form you find it
Volf- Chemical approach to glass
Helmer- secret batch recipes
Lynngard - Thuringen glass recipes
Morey- basic technologies
Hodkin and Cousin
Scholes modern glass practices
Stone -The schedules
Hot Glass information Exchange
Handbook of Chemistry and Physics
Giberson - A glassblower's companion

That's a good start. Some available still from Igneous glass but they won't be reprinted.

Pete VanderLaan 04-12-2019 11:09 AM


Originally Posted by Shawn Everette (Post 143642)

I just saw what Glassnotes 4 was going for, putting mine in a safe.

I just went to Amazon, and it's actually down a bit right now. I see a hardcover copy is $1100 dollars. I'm not aware of any hardcovers ever being printed so I doubt that. . The reprint of Volf has 20 copies in Hardcover. I gave one to Mark as a present five years back. If you are interested in the chemistry, it's the one you really should own.

Shawn Everette 04-12-2019 11:26 AM

I actually have a copy. I need to check the rest of the library.

I particularly liked "The Starving Artist's Lampwork Project Book" on Amazon. Think may be a good companion to "The Artist's Guide to Vows of Poverty".

Pete VanderLaan 04-12-2019 02:06 PM

Guard your books. I mean it.

Shawn Everette 04-12-2019 02:24 PM

I actually had glass notes at work, taking it home today

Pete VanderLaan 04-12-2019 02:32 PM

I suspected that might be the case. A few years back, I knew someone who did a workshop in an unnamed school and had their Dino Jacks lifted from the bench.

I got to the point when we were doing a lot of color doping of Hxtal to leave dyes from Conservation Materials out when we had students or visitors around. Dyes were not part of the class materials
They didn't work.
I had the good stuff put away. I did actually get calls from people trying to figure out how I was getting such nice color with them.

It's not like it once was.

Shawn Everette 04-12-2019 04:15 PM

There was a regular studio practice of leaving out incompatible color for the sticky fingers.

Pete VanderLaan 04-12-2019 04:56 PM

Uh Oh, down this path is a narrative that will scare away everybody.

Shawn Everette 04-12-2019 07:22 PM

I've had to deal with some real characters, more than one restraining order has been filed. I wonder if wood and ceramics has as much of those problems?

Pete VanderLaan 04-13-2019 09:01 AM

Actually during my classes, I only had a few problems, one drinking too much and another being a pig with the food and constantly doing things like breaking the dilatometer by deciding to take it apart. After classes, I had one ongoing problem but never anything like you describe. Scott always seemed surprised that we didn't always get at least one major jerk.

Shawn Everette 04-13-2019 09:31 AM

I was dealing with a lot of legacy people. The kind that feel like they're owed something when they really do nothing. This was a public facing studio and there were people drying their clothes in front of the furnace and letting their dogs shit on the floor. Plenty of verbal abuse and physical altercations on occasion. There was also the issue of self medication when you should have taken the drugs you were prescribed. For some reason this level of behavior was tolerated after the 80's, things were due for an update and I was an agent for change. After tightening the ratchets things calmed down considerably, locks and cameras keep people honest. Think there was something in the water, cause yes, nothing close to that was acceptable elsewhere.

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