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  #26  
Old 05-22-2018, 09:36 AM
Dan Vanantwerp Dan Vanantwerp is offline
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Round 3

Pushed the LEC to 88.7 this weekend. The phosphate strike remains the same with a solid white coming up after just 1 or 2 reheats. Very nice color. I also feel like I'm getting better at melting this glass with multiple stirs and a long higher heat to 2180 (8-10 hrs).

The compatibility tests with Cristalica were consistent for 2 cyclinders each; Brossphate inside clear and clear inside Brossphate. The encased Brossphate again made it out of the annealer but still cracks on the saw. Brossphate over clear does not even make it to the saw. Cracks shortly after removal from the annealer.

I'm going to drop the LEC to Jordan's 87.8 LEC number for a 5% phosphate glass...even though mine is at 3.2%. I believe the expansion is being driven by the saturation of tiny PO4 bubbles. A 5% might get to saturation faster, but a 3.2% gets there eventually. Either way, the final result on expansion is the same (I hope).

This brings up some interesting issues with using this glass. See the Gaffer Glass tech notes:
http://www.gafferglass.com/technical...paline-series/

This glass has the potential to change it's LEC based on the work time and reheats. I suppose it is possible to land on an LEC somewhere between a dense and veiled opal (good luck). Working with it alone is a possibility but at some point it begs to be married with your favorite color patterns.

I started wondering if this is happening to some degree with all opal glasses we use. This Brossphate is making me think about glass in different ways. It's been a great experience and I look forward to getting a fit. Not sure it will work for encasing/overlays and I wonder if Jordan or Dave ever got it working in this capacity...
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Old 05-22-2018, 09:51 AM
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Pete VanderLaan Pete VanderLaan is offline
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It is not the same as with other opals. Your phosphate is a phase separation glass: One phosphate glass embedded in a silica glass. On reheat the phases separate leaving a bazillion fine bubbles to reflect light.

A fluorine opal is very different, using fluorine to combine with either alumina or calcium to make crystals that are in the glass. If you didn't have the alumina or the calcium, it wouldn't make the crystals. Those crystals grow, collapse and grow again as the glass winds down its intensity.

If your samples are either breaking up on the saw, or just by themselves, You are likely at least two full points out on the mismatch, perhaps more.
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  #28  
Old 05-22-2018, 01:37 PM
Dan Vanantwerp Dan Vanantwerp is offline
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The Brossphate on the outside is even less compatible than when encased with clear. Does this tell you anything about the direction I'm off?

Thinking of dropping it down to 87 or even 86.5. The current batch was less runny than previous versions but it's still very workable. Does seem to be shortening the work time, however.
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  #29  
Old 05-22-2018, 02:37 PM
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It seems to me that if the glass on the inside has a lower expansion, it's more tolerant. You should probably try something radical like changing the soda by around a half percent and see what it does.
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Old 05-22-2018, 04:02 PM
Dan Vanantwerp Dan Vanantwerp is offline
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Thanks Pete. I was hoping that might provide a clue. I'll give it a shot.
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  #31  
Old 05-24-2018, 10:28 AM
Dan Vanantwerp Dan Vanantwerp is offline
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Revised analysis

Last weekend, I made a cylinder with chalcedony on the outside and Brossphate on the inside similar to the Cristalica compatibility tests I ran. I let it sit a few days before running the ring test. Almost did not bother after my previous results. Survived the saw, made rings and had no movement in the vertical crack test. Looks right on.

The Cristalica versions were run a couple hours after being pulled out of the annealer. They were cool and I thought "done". Going to repeat the tests with a longer cool time. I really don't think the Brossphate outside results will change. Both my tests cracked an hour or so out of the annealer. I have a rather long annealer cycle as I was using it to try and coax more colors from the chalcedony glass. I think it's allowing for a good strong annealing. We'll see what happens If I leave it alone for a longer time.

I am posting mainly to let others know about the timing difference. I'm new to ring tests and was really surprised about the possibility that annealed was not "ring-test ready" annealed. Learning...
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  #32  
Old 05-24-2018, 01:29 PM
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If a piece can't survive sitting by itself after being out of the lehr for two hours, it really is not close to being compatible unless you're talking some massively thick thing. A regular glass, in the shape of a cylinder, about 1/4-1/3 inch thick, about three inches in diameter will do admirably. Do make sure your saw has adequate coolant and the blade has diamonds on it.
If the piece cracks, almost with a shudder, the moment the blade touches it and breaks the surface tension, you were way far off. You really should be able to saw the ring ( about an inch inch wide). My experience tells me if the ring survives that, it's compatible. I've seen some exceptions marrying lead to soda lime where it can take an hour or so to crack after that but in general, similar glasses are good matches at that point within the constraints of 1.5 ten thousandths. The vertical score that you tap clean is going to tell you how to fine tune the glasses and we outlined that as a graphic in glass notes, so look at the graphic.

John prefers the Hagy seal and I get that. It's worth noting that if the Hagy seal is more than about 2.0 off, it breaks before you can ever test it. The ring doesn't have quite the same issues. If the glasses are similar, you can do a simple pull test with canes and they will tell you a lot as well. They're in the lassnotes IV as well. If you don't own the book, you really need to get it. Henry put together a great compendium.

At any rate, you don't need to cool it that long. I just put mine under cold water before sawing if I think it's a bit warm. If that breaks it you need to change your glass.

Do keep in mind what annealing is doing and the range in which it happens. From deformation point down to Strain point, you can relax the inherent tension in your glass. Soaking the piece is the most critical aspect of the process. Putting it away hot enough to not need to overcompensate is important as Frank Wooley noted long ago. The thickness and the rate of reduction of temperature are indeed important down to Strain Point but remember that once you pass Strain Point, no further annealing can occur. At that point you're just trying to prevent thermal shock.
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  #33  
Old 05-24-2018, 01:35 PM
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Quote:
Originally Posted by Dan Vanantwerp View Post

I am posting mainly to let others know about the timing difference. I'm new to ring tests and was really surprised about the possibility that annealed was not "ring-test ready" annealed. Learning...
********
I don't know why you say that. If the piece is annealed and room temperature, it's ready to attempt sawing it.
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  #34  
Old 05-24-2018, 03:44 PM
Dan Vanantwerp Dan Vanantwerp is offline
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Thanks for giving me some feedback Pete. I thought my process for testing the rings should be ok but last night's result really surprised me.

I'll keep your points in mind when I test again this weekend. I do have Glassnotes and will look over the relevant sections.

Thread tests looked fine which also puzzled me, but I noted that it's not the most definitive test out there.
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  #35  
Old 05-24-2018, 04:36 PM
Kenny Pieper Kenny Pieper is offline
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I hear people all the time express that they leave their pieces for days to "rest" before cold working them. This is simply not necessary. Once the piece is room temperature it either has stress or not. In fact once it gets through the strain point their can only be temporary stress introduced to the work. So cooling too fast after the stress point will either break the piece or not but you will not be giving it a stress that is lasting. The same is true after the piece is room temp. You can cause stress in the glass by heating it too much while cold working or other aggressive actions, which can break the piece, but you will not be giving it permanent stress.
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  #36  
Old 05-24-2018, 05:34 PM
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listen to Kenny
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Old 05-29-2018, 10:00 AM
Dan Vanantwerp Dan Vanantwerp is offline
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round 3b

I ran the Brossphate 3.2% @ 88.6 LEC again just to be sure all my compatibility samples were run in the same way. I am testing it versus Cristalica and Pete's silver opal batch (chalcedony). Pete puts Cristalica at 97 LEC and my estimate for the chalcedony is 94.1.

I was afraid that I was complicating issues by testing against 2 glass formulas but now I am glad I did. It allows you to make the expansion variations and find fit where it occurs rather than starting all over again with another test. You are also using the exact same glass and can erase any questions about batch formulation.

The chalcedony is matched to this glass...inside and outside. Brossphate over Cristalica still fails before it gets to the saw while Cristalica over Brossphate fails after a few inches of radial cutting on the cylinder. I could get a solid ring from the top of an open cylinder. It contracted a bit after checking the ring. Both results suggest that the Brossphate is lower than Cristalica. I'll bump the Brossphate up to 91 (as Jordan originally suggested) and retest. I ran a 90.2 a few weeks ago and did not find fit so kept going down. We'll see what happens.

My worry is that Cristalica-Brossphate-Chalcedony will not fit all together. This combination is really fantastic and I looked forward to contrasting the opal swirls against a variety of Brossphate color backgrounds. I can still do that but without a clear encasing which really finishes off the chalcedony.

My other option is to change the clear. This may be the final nudge I need to do so.
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Old 05-29-2018, 11:03 AM
Eben Horton Eben Horton is offline
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Donít change your clear. Thatís asking for nightmares down ththe road.
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Old 05-29-2018, 12:49 PM
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Do thread tests for a quick idea of where you're at, then more advanced testing when the threads are looking good.

http://www.davebross.com/GlassTech/g...litypage2.html
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Old 05-29-2018, 12:59 PM
Dan Vanantwerp Dan Vanantwerp is offline
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Thanks for the warning, Eben. Point well taken. However, I'm considering myself as starting down the road at this point (15 years in). Small batch color is the way for me to go. Besides, I've already had to change my clear 3 times based on the availability of cullet. I can make a clear with Pete's unoxidized (base for the chalcedony) easy enough. Also hoping to try the newest version.
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  #41  
Old 05-29-2018, 01:08 PM
Dan Vanantwerp Dan Vanantwerp is offline
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Hi Dave. Thread tests didn't tell me much. Everything was straight as could be. I just sort of slap gathered a dab of cristalica next to a dab of Brossphate. I even brought out the phase separation to make sure I was looking at the final glass. Worked great without having to get out a torch. You could see the even pull of both colors coming into the thread.
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Old 05-29-2018, 02:10 PM
Eben Horton Eben Horton is offline
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If you pull a pull test and then give it multiple flashes, you are re annealing it and might be fooling your results. Iíd get it it hot, pull it, and then let it cool. Thatís it.
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  #43  
Old 05-29-2018, 02:48 PM
Dan Vanantwerp Dan Vanantwerp is offline
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I have to say that I tried a few different ways. I gathered a little clear then a little brossphate side by side. One time I pulled the thread right out of the pot, but also tried it after cooling and heating a couple times. The threads were never reheated just the side by side gobs on a punty. No matter what they just stayed straight as a string.

Ring test is much more telling.
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Old 05-29-2018, 03:42 PM
Kenny Pieper Kenny Pieper is offline
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Quote:
Originally Posted by Dan Vanantwerp View Post
I have to say that I tried a few different ways. I gathered a little clear then a little brossphate side by side. One time I pulled the thread right out of the pot, but also tried it after cooling and heating a couple times. The threads were never reheated just the side by side gobs on a punty. No matter what they just stayed straight as a string.

Ring test is much more telling.
You are right that the ring test is much more accurate.
When it comes to the thread test I think you need to start at the same temperature and amounts. In you case I would gather some of the opal on a punty, strike it, marver it out into a finger shape. Then gather the same amount on another punty shape it the same, stick the two together and heat them a couple of times to make sure they are the same temp before pulling them. It sounds like you base glass and the opal are not necessarily similar formulas so this may not tell you all that much.
If the two glasses are simular this will give you a good start
I have a very dense black that I make that is quite soft and if I make a thread test that is straight I know that it is incompatible.
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  #45  
Old 05-29-2018, 04:17 PM
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Chuck used to say "Sometimes you're so far out, you're in".

The ring test and the Hagy seal just don't calm your lying eyes. They speak truth.
Quit trying to calm yourself with "the on the outside it's better than on the inside. ".

It's better when you just saw it and it cuts clean.
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Old 05-29-2018, 04:42 PM
Dan Vanantwerp Dan Vanantwerp is offline
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Thanks Kenny. I thought of making a couple rods and then performing the thread test but figured it would work fine from side by side gathers. The heat was definitely the same as they were on the same punty. Amounts were variable, though. I would try and refine it for a more accurate deflection measurement but there was just no bend.

Hard to say how different the Brossphate is from Cristalica but given their purposes I would say they are likely quite different.

Pete,
I can cut a ring from cylinder that is layered...Brossphate-Chalcedony-Cristalica. No stress is indicated in the ring test.
Knowing there is stress, but that it is somehow offset in the layering, I do not plan on using this combination. Should a successful ring test bring me calm in this instance?
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Last edited by Dan Vanantwerp; 05-29-2018 at 04:44 PM. Reason: mistaken glass combo
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  #47  
Old 05-29-2018, 05:58 PM
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Don't forget to evaluate your basic pieces. How do the individual glasses do in the saw with no laminations at all?. Sometimes the annealing is the thing overlooked.
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Old 05-29-2018, 10:54 PM
Dan Vanantwerp Dan Vanantwerp is offline
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With so many failed ring tests I used a self over self layered glass to test my sawing technique. Worked fine and Brossphate by itself sawed great. Annealing is good. I think I may just be happy it is matched to the chalcedony and move on.
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  #49  
Old 05-30-2018, 09:56 AM
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Weyl suggests that chalcedonia is actually easier in a phosphate base. If you don't have weyl ( Coloured Glasses 1951, 1954 ) , get it. It's a very though read, particularly compared to Volf but in actuality, Both authors are quite dismissive of silver bearing glasses except in silver staining. It is a real fugitive and despite rigorous control it's going to give you a good deal of heartache for no discernable reasons.
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Old 05-30-2018, 10:10 AM
Dan Vanantwerp Dan Vanantwerp is offline
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I threw about 50g black tin into ~20 lbs Cristalica cullet and used that to encase the chalcedony. Seemed to bring out some more opacity. Also loved the way silver chloride nuggets flowed over it. Is there a simple addition to help remove the yellow tint?

I'll look for Weyl.
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