Evaluating cullets and such

[Pete VanderLaan]

Originally Posted by Mark Rosenbaum

They need to be pre-heated. Any piece of glass of any size needs to be pre-heated.

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More cost.

[Kevin McLeod]

Originally Posted by Pete VanderLaan

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More cost.

Is it? From my memory it takes the same amount of energy to heat a material from room temperature to melting regardless of what box it's in...

[Pete VanderLaan]

well, OK, you're charging cullet. You plan to preheat it. In what ? Are you turning on an annealer and doing it in there? If not, where? If a second tool has to get turned on to heat the cullet, then I'd suggest more cost. What a preheat does do well is to take thermal shock off the pot.

I don't have any particular agenda here at all. I wanted to look into what it costs to buy glass and to melt it these days. If you have 300lb pot it sounds like it can cost up to $600 dollars to fill the pot without thinking about the fuel cost. If the cullet turns cordy easily, that's worth considering.

For me, that's a shitload of money in a somewhat weakened economy going downhill fast.

I'm just trying to shed some light on the subject. I'm not selling batch or cullet. I do remember when cullet was .02 cents per lb.

[Mark Rosenbaum]

Originally Posted by Pete VanderLaan

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More cost.

What I am saying is that any cullet of size needs to be pre-heated to prevent popping. I am lucky enough to have a large lehr that has 1/2 allocated for work, and 1/2 allocated for the cullet pot.

[Pete VanderLaan]

OK. Is it not the case that if the annealer was smaller it would cost less to run? I'm not trying to be difficult, I'm trying to see what this costs as objectively as I can. I understand that hot cullet doesn't pop and that hot cullet is way easier on your crucible. I don't view it as any big issue.

Something I've seen in cullets is that some are far more prone to cording after a few days and that can be pretty undesirable in a big pot if you can't use it up. Some are worse than others.

[Eben Horton]

I have never seen cords in my Bomma melts. Bubbles, yes…. But never cords.

I’d go back to sp 87 tomorrow but I just don’t want the dust in my studio.

[Pete VanderLaan]

That's good to hear. I expect bubbles at this point since one way of keeping costs down making the goop is to spend less time in the furnace melting. Short melts are what caused the borax clogs we were seeing in Spectrum 2.0 where you could watch the furnace door rock when gas escaped from studio furnaces clogging the element vents on Moly's and the recuperators on gas units.
As costs go up, I expect to see more and more marginal quality in what you get.

I'd like to know what others experience with other cullets.

[Eben Horton]

The bubbles are simply from air being caught between the pucks of cullet when melting. You can’t squeeze them out. You have to charge slow and throw in shallow layers and then you are fine. The quality of the stuff is great. (For now)

[Pete VanderLaan]

I interpreted your statement about the bubbles as being in the actual cullet. what you describe is normal. Bomma still contains the antimony. You might be well served giving the glass a good stirring with a potato when the charge is done, unless it's simply never really getting turned up in the first place.

[Franklin Sankar]

Thanks for that explanation Eben. I always thought that you squeeze to get rid of all kinds of bubbles .
Franklin

[Michael Ahlefeldt-Laurvig]

Franklin,- its sort of Yes, No, Maybe, sometimes, depends,, there is no clear answer

[Michael Ahlefeldt-Laurvig]

Franklin, when youre doing a Murano dolfin goblet with a dragon on top, you can adress seeds ok?

[Pete VanderLaan]

And it needs to be a male dolphin, uncut.

[Art Freas]

Originally Posted by Eben Horton

The bubbles are simply from air being caught between the pucks of cullet when melting. You can’t squeeze them out. You have to charge slow and throw in shallow layers and then you are fine. The quality of the stuff is great. (For now)

Agree in all points. The shallow charging is supper important.
Art

[Pete VanderLaan]

well, how hot are you letting it get and for how long? I always had a terrible time trying to fine out Cristalica during the brief period I tried to evaluate it.

[Scott Novota]

I guess I just hold my mouth right. I dump in the Bomma at 2050f and walk away and have seed-free glass the next day (14 hours later [2+/-]).

Then again, I only charge about 15/20 lbs at a time over the day when I think about.

I would guess there is a good hour+ between those loads.

[Art Freas]

Originally Posted by Pete VanderLaan

well, how hot are you letting it get and for how long? I always had a terrible time trying to fine out Cristalica during the brief period I tried to evaluate it.

Often and shallow, if you do it shallow it fines out by next day. We charge every day so we can charge shallow. At most we charge about 2 - 2 1/2 inches melted down a day. Weight doesn't matter but depth does. We work and charge at 2150, if we are charging thicker we do run it up to 2170, but that is rare.

[Philip Yamron]

Just FYI Spruce pine everclear went up in price the 1st of this month. New price is $1.20 per pound.

[Pete VanderLaan]

Originally Posted by Philip Yamron

Just FYI Spruce pine everclear went up in price the 1st of this month. New price is $1.20 per pound.

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Expect to see more new pricing at new year's

[Michael Ahlefeldt-Laurvig]

Well no ,depends on your furnace eh?

[Pete VanderLaan]

Originally Posted by Michael Ahlefeldt-Laurvig

Well no ,depends on your furnace eh?

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I can't tell what you're referring to Michael.

[Michael Ahlefeldt-Laurvig]

Well both the talk of melting small amounts shallow and preheating cullet. My electric furnace with molybdenum electrodes in the glass created tremendous convection with really hot glass around the two electrodes rising to the surface and cooler glass falling along the sides of the tank. A freestanding pot also stirs the melt better than a top fired tank furnace would. And the two furnaces Ive built were totally impervious to exploding cullet spatter. My pot furnace had a bowl like construction so where the wall bricks connected to the floor castable 10 cm above the floor level at the smallest distance. Thus no glass donut in the insulation. And the whole floor leaned so any glass running on the floor followed the flue out to a chamber outside the actual furnace room, where it could be cleaned out when needed. That chamber was also sized to take a full pot of glass rupturing leaving the pot and combustion chamber unaffected. Because of this design the furnace actually stood 50 cm below the rest of the floor in the studio. Ive never bought cullet, but would add my own clear scrap when I had.

[Brian Bradshaw]

I decided to try Bomma on my first melt in my new Paragon Vulcan II (wire melter). Ordered three bags to try. With shipping, came out to
$2.33/lb. Gas here is $6.25-6.50/gal. Don't know about Washington, but the shipping into the state reflects our gas costs here. Just sayin...

[Pete VanderLaan]

There is a glass shop in Bristish Colombia that has used SP for years as a batch in a homemade wire melter. It works great. Doesn't lose elements. I watch the economics of all this from where I sit and I talk to a lot of folks. I think that cullet will go back into crisis, likely this winter. I tend to think that one, perhaps two clear cullets won't be around next summer. The one I see remaining is a terrible glass. That's based around mismatch.