View Single Post
Old 12-08-2003, 01:36 AM
Parker Stafford Parker Stafford is offline
Registered User
Join Date: Apr 2002
Posts: 254
Parker Stafford is on a distinguished road
I tend to feel that how your furnace is set up will determine how well it performs. How close are the elements to the glass line? Are they above or below the pot? How well are the elements protected if they are below? Watt loading is important. How much dust they will get on them, or popping cullet is a concern and a consideration. Being able to use your eyes and powers of observation are important in a wire melter. Learning to see a dying element a month before it happens is not hard to develop as I do it all the time. Every now and again, something will come along that will f--- it all up, like a long power outage, or bad metal in the wire. I believe this has happened once in the seven years I have had this furnace.

I think that preheating batch is okay if you can also keep the batch wet, which gets to be tricky when you go up to around 900 degrees or so. I used to preheat, and it did help with speeding up the melt, but since my elements are above the pot, I was getting dusting, and this was not good for the elements. No free lunch. You gain in one area, lose in another. I am not about to step into the sweet smelling mess that is the moly/wire debate. Do what works for you in your situation. When it no longer works, cast about for something new. The bottom line is that you enjoy it and are able to make good work. If any of those is off, something needs fixing. If your furnace is giving you trouble, maybe it is design related, maybe it is time for something new.

You can melt batch pretty cool, but you need more time. You can also melt it hotter, but you might lose a little on wire life. Take your pick. I know a guy who never turns his wire unit up to charge temp. He owns a flat glass business and 80% of his business is doing large plate for restaurants, custom installs, etc., so he can charge after using up a pot, then come back to it a number of days later. Says if he has enough time, the glass is perfect. He also gets real good element life.

I find that the best squeeze comes from a drop to 1900 degrees IN MY UNIT. If I do a drop to 2000, I need an extra day for it so sit (again, in my unit)in order to get paperweight quality glass (the bar is lower for some blown things), and have done it like this when I went off for the day knowing I would not be blowing.

Electric will always tend to be more bubbly in my opinion as a result of the atmosphere. It is regular earth atmosphere, not a mix of hydrocarbons being combusted. So take that into consideration Actually, batch is ALL I melt, and I do the melt starting at 2280. I go up to that, and I charge about 50 lbs at first in a 130# capacity crucible. No preheating the batch, and no strict adherence to a 30# only charge size. Then I drop the temp down to 2220 and do the middle charges at that temp. Then before I do the last charge, I ramp back up to 2260-80 and let it soak there for about 4-7 hours (after the charge), although I might go longer if I have the time. If I had more time I might keep the temp down around 2230-50. I keep my high temps in short duration, but I believe in them for getting gasses to expand for fining. I like to have a six hour squeeze before turning up to work temp. If your unit takes a while to drop in temp, like mine does, you need to take that into consideration for the tail end of your "melt" which is your squeeze. Early on I realized that it took my furnace about 5 hours to drop from charge temp to squeeze temps., and when I adjusted the melt to take that into consideration (for the time actually spent at around 1900 F.), the glass quality got much better. I was going in the evening to turn the furnace down, and often it was late enough that the unit did not have enough time to get a good squeeze in before the a.m..

How careful I am about the melt depends on what I am making. If I am doing solid, I am very anal about how I do the melt. I also stir the glass with a spud as it is the most convenient way to mix the glass in my opinion and get very good evenly mixed glass of top quality. I once saw a guy mixing his melt using a punty attached to a drill. I tried this, and found it to be a big pain in the ass (this was a big studio). It actually got more bubbles in while not really mixing as well as I would have liked. Do the mix at a high temp so you get some real life agitation. I am talking in the 2220+ range. Hotter the better, in my humble opinion, as the glass mixes so much more readily. The glass comes out much better, even when you have a crucible in good shape. When the crucible is in bad shape, you are kind of trying to make a purse from a sow's ear. Sometimes it can work.

Parker S.
Reply With Quote