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-   -   now that there is a choice (http://talk.craftweb.com/showthread.php?t=12481)

neil duman 11-26-2019 09:07 AM

now that there is a choice
 
Not looking for any comments on batch v cullet.
I would like to hear from folk who have been using the Bomma or Kugler cullet.
I rather not have to ramp up to 2150 to charge cullet.
I batched at 2250 when I did batch.
Any info is appreciated.
Thanks

Jordan Kube 11-27-2019 10:07 PM

A lot of people work their glass close to or at 2150. I wouldn't try to melt cullet much colder than that and expect good results.

I can't give you the comparison on bomma vs kugler but I have worked with the bomma. It struck me as a very long working glass. Probably close to spruce. I've been using mostly spectrum products and cristallica over the last few years.

David Patchen 11-28-2019 10:42 AM

Bomma is probably the nicest glass I've worked with and I've worked with a few. I think 2150 is a good starting point to work at (every furnace varies). It's an easy glass to blow and has been compatible with all the gaffer, reichenbach and sys 96 rods I use. It's always hard to explain working properties, but I'll try: Bomma is very linear in it's behavior, fairly long-working, 'creamy' and viscus and soft when hot rather than wet/sloppy. It reheats easily and stays a bit thicker even when really hot, so cane pulling feels easier vs. other glasses. It's really clean, bubble-free when properly melted and I'm really glad we switched. I don't miss the Spectrum 2.0.

Michael Ahlefeldt-Laurvig 11-28-2019 06:37 PM

2150 is a good blowing temperature, you dont have to ramp anywhere, the cullet will melt nicely, although Ive never tried just those

Pringle Teetor 11-29-2019 07:35 PM

Ive been hearing stories of chords in the Bomma. Have you seen any?

Pete VanderLaan 11-30-2019 05:49 AM

Chords come using musical instruments. Cords are inhomogeneities in glass.

It would not surprise me to see cording when you are switching from one glass to another. Cleaning your pot well, then running one wash load, throwing that away and then just melting should yield a reasonable glass. People don't like throwing away glass at $1.50 lb.

It's a cost of doing business.

Josh Bernbaum 11-30-2019 12:59 PM

Quote:

Originally Posted by Michael Ahlefeldt-Laurvig (Post 146096)
2150 is a good blowing temperature,

Maybe it is, maybe it isn't. I felt compelled to chime in to say it depends on what one is making and one's unique furnace/unique thermocouple.

Michael Ahlefeldt-Laurvig 11-30-2019 07:17 PM

I have an optical thermometer, it matches a glowing wire to whatever you aim it at, so I dont have to be questioning the temperature. But ok Ill agree to a small extent that what youre making could demand a small change. The main point I was making was that 2150 works fine to melt cullet overnight, at least my own Glasma. It seems odd that you would have to ramp up to a normal working temperature to melt cullet

Pete VanderLaan 12-01-2019 11:38 AM

Quote:

Originally Posted by Michael Ahlefeldt-Laurvig (Post 146104)
It seems odd that you would have to ramp up to a normal working temperature to melt cullet

*****
It would depend greatly on whether the cullet was formed from a mix that had actually completed it's chemical reaction Michael. If it hasn't, then it would need the sustained heat.
Not finishing the reaction, on the makers part is a good way to cut costs and pass the process of proper melting on to someone else.

The other reason would be the viscosity of the glass itself.

Bob Meyer 12-01-2019 12:27 PM

We used the first version of Kugler, the "Kugler Clear", and that worked well for us. Nothing notable, but the Cristalica has been changing - got all sorts that had rust coatings.

More recently, Kugler came out with the "Free" (boron and lead-free), of which we're just finishing the first pallet. It's been my personal favorite so far - a good, long working time, though not runny at the start - much the way David describes the Bomma. Seeds are rare, quite unlike the way Cristalica was getting to be for us.

One difference for us is that we melt at 2050 - just leave it at 2050 all the time. We've just always done it that way and have always gotten desirable results. We've found that we do have to pre-heat the Kugler Free - it pops like firecrackers going into the furnace cold - but pre-heating didn't turn out to be the ordeal we anticipated - no popping whatsoever going in, and great quality glass in the morning.

By the way, Hot Glass Color also discounts the Kugler color if you get your cullet from them. Great deal.

David Patchen 12-01-2019 01:35 PM

Quote:

Originally Posted by Pringle Teetor (Post 146100)
Ive been hearing stories of chords in the Bomma. Have you seen any?

I haven't seen many, but we washed the pot well before switching and our pot was in good shape. Pots that are pitted don't wash so well and continue to hold the old glass (and dissolve more pot) in the nooks and crannies, so more cords.

I think if melted well in a newer, well-washed pot, the Bomma should be cord-free and really nice.

Shawn Everette 12-02-2019 12:36 PM

We've been cord free with a washed pot. Little seedy next day, but we melt and gather at 2080.

neil duman 12-05-2019 07:58 AM

Quote:

Originally Posted by Bob Meyer (Post 146111)
We used the first version of Kugler, the "Kugler Clear", and that worked well for us. Nothing notable, but the Cristalica has been changing - got all sorts that had rust coatings.

More recently, Kugler came out with the "Free" (boron and lead-free), of which we're just finishing the first pallet. It's been my personal favorite so far - a good, long working time, though not runny at the start - much the way David describes the Bomma. Seeds are rare, quite unlike the way Cristalica was getting to be for us.

One difference for us is that we melt at 2050 - just leave it at 2050 all the time. We've just always done it that way and have always gotten desirable results. We've found that we do have to pre-heat the Kugler Free - it pops like firecrackers going into the furnace cold - but pre-heating didn't turn out to be the ordeal we anticipated - no popping whatsoever going in, and great quality glass in the morning.

By the way, Hot Glass Color also discounts the Kugler color if you get your cullet from them. Great deal.

Thanks for the reply, from the earlier responses I was thinking we were odd to melt and work the cullet at 2050.
I guess I need to give Hot Glass a call.

Greg Vriethoff 12-05-2019 04:31 PM

Quote:

Originally Posted by Bob Meyer (Post 146111)
We've found that we do have to pre-heat the Kugler Free - it pops like firecrackers going into the furnace cold - but pre-heating didn't turn out to be the ordeal we anticipated - no popping whatsoever going in, and great quality glass in the morning.

It is also important to note something else about popping. When you throw large chunks of any cullet into a furnace the shattering from thermal shock introduces thousands of tiny gaps that trap air. You're introducing more opportunity for bubbles that are only going to force you to fine for longer at higher temps.

I'm going to guess this is just one factor that may be contributing to better glass quality for Bob.

Pringle Teetor 12-06-2019 06:53 PM

I knew it was cords but my spelling corrector didnít have a clue what I was talking about :)

Pete VanderLaan 12-06-2019 07:53 PM

Quote:

Originally Posted by Pringle Teetor (Post 146202)
I knew it was cords but my spelling corrector didnít have a clue what I was talking about :)

****
Kept you up nights did it?

Bob Meyer 12-10-2019 02:01 PM

Quote:

Originally Posted by Greg Vriethoff (Post 146162)
It is also important to note something else about popping. When you throw large chunks of any cullet into a furnace the shattering from thermal shock introduces thousands of tiny gaps that trap air. You're introducing more opportunity for bubbles that are only going to force you to fine for longer at higher temps.

I'm going to guess this is just one factor that may be contributing to better glass quality for Bob.

That's what I would think, too. But you would think, then, that Cristalica, coming in much smaller pieces, would be nice and seed-free. For us, it was just the opposite - the seeds with Cristalica were more pronounced than with any other cullet we've ever used.

As for the pre-heating, we've used both the Kugler Clear and Kugler Free. We started with the Kugler Clear during the time Cristalica was unavailable, and did not pre-heat it because it didn't pop much more than the Nuggets. Even loading them in there cold, we immediately noticed essentially a disappearance of the seeds with the Clear - and there were some pretty big chunks! However, when they broke, they seemed to totally break apart rather than craze. The pre-heated Free seems to actually craze quite a bit if they cool too much (fall on the marver or floor), but the glass continues to be essentially seed-free.

From this admittedly limited experience, it seems that the greater amount of space between smaller pieces of cullet will trap a greater amount of air as the cullet melts. On the other hand, when the large rods of Clear cracked from the shock, they usually broke in whole chunks, exposing a limited number of new surfaces to the air. Once the cracking was done, you could see whole large, intact chunks of cullet melting.

Rick Kellner 12-10-2019 03:05 PM

Definitely seems intuitive that the interstitial spaces relative to the size of the cullet would play into seeds in the glass, or lack therein.

Greg Vriethoff 12-12-2019 12:07 PM

Intuitive, yes, but not necessarily a definitive "solution." I know there are a variety of reasons for seed formation. In my experience everyone has their own voodoo that works for them.

My hope is that any "good" quality cullet that is coming out of Cristalica's competitors can be consistent. Once demand increases the quality could be affected.

Pete VanderLaan 12-12-2019 01:21 PM

Quote:

Originally Posted by Greg Vriethoff (Post 146262)
Once demand increases the quality could be affected.

****
And that's the problem in a nutshell. I would imagine that any factory with excess capacity would be really happy to make such stuff if their regular clients were having slow times. It's what happens when things pick up that become the problem. There's a lot more money in finished wares.

Glassblowers have always suffered from telling too many people about good things when they find them. Once upon a time, Keystone cullet was fabulous at .02 lb but it turned to shit as more and more people wanted it.

Cristalica was underperforming when Kuchinke and I first began to talk about it. They had been melting in Romania and moved it to Dobern to a five ton unit. When Spectrum finally ran out of product, demand went through the roof and the furnace was pushed to 7 tons which it can't sustain and you have seen what occurs with the product. The big concern will be the status of the Bomma as demand shoots up. I continue to think that it's essentially nuts to be shipping cullet across the Atlantic. Even at $1.41 lb, there's not much money to be made there. I don't see the product from Oceanside being particularly viable as long as they make what they are making. For an industry that claims it wants to serve it's clients, it's fairly bizarre.

As to seeds, there's lots of reasons seeds can be in glass. Incomplete melts cost less upfront but you pay for it later. Trapped gas is real as well, so is dust. Tiny cracks are really stubborn.


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