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Old 12-18-2017, 12:09 AM
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a simple How To make Hagy Seals

Someone explain the right way to do a Hagy seal test for me, and who Hagy is/was.
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Old 12-18-2017, 09:14 AM
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Make a rod of your clear glass, of whatever host glass you use. Make it 4mm in diameter. Draw out a cane of your other glass you want to test the same diameter. Cut the canes to about 1.5 inches in length. Place two of the canes of the clear on the outsides of the color cane like you were making a sandwich. Now with a torch, fuse the ends of the cane to each other- just the ends. Now anneal it and bring the cane out of the annealer and put it, completely cooled on the table of a good quality polarimeter with the lower plate in full retardation axis with back light. Holding another piece above the subject cane, observe the seal and begin to rotate the film or plate you are holding in your hand. The cane color will begin to darken and at it's darkest point you can measure the number of degrees of rotation it took to gain that amount of retardation. If you get more than five degrees, you have a mismatch. Depending on where you rotate clockwise or counterclockwise determines which way you are off.

The real difficulty here is measuring those degrees. My Polarimeter came from Strainoptics and costs over two grand. Croucher has the same unit. It measures by single degree in either direction. Not a tool you can really justify owning unless you make color for a living. Not unlike owning a crusher. The other thing about hagy Seals is that if you are not quite close on the mismatch, the seal simply breaks and it does it easily. Then you have nothing and it's why I continue to prefer the ring test which is indeed more subjective than the Hagy seal. The seal is absolutely on the money.

In the ring test, take a gather of your color and case it in your clear. Blow out a thin cup and anneal it. When cool, place it in a diamond saw and cut off a ring of the cup. If it actually survives this act, chances are good the two glasses are compatible with each other. A disturbing number of color rods will fail and break at this point if worked with a so called 96 LEC glass. But if it does survive, make a vertical score across the ring with a glass cutter and tap open your score. If the ring opens with a small gap, it's telling you that the interior glass has a lower expansion than the outer glass. If it tries to overlap the opposite is true. The trouble with this test is that you now know you have an issue but since you don't make your own clear, or color, there's nothing you can do about it. At least you know what kind of long term bombs you may be producing.
In general, Gaffer really has the best track record. Kugler opaques have the worst with most opaques testing around an 89. Reichenbach is good on transparents. Effetre can be incompatible with itself. It's the clear manufacturers that are the real source of trouble. When they change, the earth shakes from breakage.

Hagy was a materials Engineer at Corning. You can read more about him here:
https://www.cmog.org/library/glass-s...-compatibility

You will find the seal discussed very thoroughly in that ever popular yet hard to find book "Glassnotes IV by Dr Henry Halem. It is out of print. I suspect Henry could be coerced to supply the pdf pages on the seal for a fee. You could ask him. Frank Wooley and I really covered the gamut of testing for mismatch in that book. I don't think any serious glassworker should be without it. It's only in the 4th edition. Owning the 3rd is worth it as it had a good deal of good stuff that was removed in the 4th.
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Old 12-18-2017, 12:15 PM
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I left all my books back on the mainland
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Old 12-18-2017, 01:35 PM
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Ask Bill Worchester if you can use his. Sadly, I just looked on Amazon and there are 8 copies all starting at $450 dollars and two new copies at $750.00. I would imagine I could sell my hardbound Weyl and Hardbound Volf for a lot less. No lurid pictures.
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Old 12-18-2017, 06:59 PM
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So, is this clear? If it isn't tell me and I'll try harder to explain. You really need to give your materials the decency of understanding them. No foul here at all.
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Old 12-18-2017, 10:07 PM
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I umpterstrand. Gonna fly in the face of a bunch of good advice and test system flat glass against spruce pine batch. I've just got a jones for it. Probably will post some results on this thread.
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Old 12-19-2017, 07:41 AM
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testing is always good.
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Old 12-19-2017, 03:00 PM
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Think I'll snag that copy for $3,214. Whatta bargain!
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Old 12-19-2017, 03:02 PM
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well, I just got three different POGO books from the 1950's for under fifty bucks. I'm pleased. But then again. Walt Kelly is dead.
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Old 01-12-2018, 06:41 PM
Bradley Howes Bradley Howes is offline
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When I was taking a class with Gianni Toso, he made a ring test. Instead of waiting for the glass to anneal, he cooled it in air, then put on a wrap and dunked the cylinder in water. He did that again so he had about a 1 thick ring. Then finally placed a red hot punty across the ring and dunked it. Then read the results. Would this be valid?
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Old 01-12-2018, 06:59 PM
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It's one of the ways to do it. It isn't quite as easy as you make it sound though. What it does do is give you a real time evaluation of the day's melt.
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Old 01-12-2018, 07:15 PM
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I'm obviously doing the ring test wrong. For starters, I don't melt color, so the ratio is more like 10/90 color to clear. I made some rings, and they didn't do any of the overlap or gap thing.
I did make some solid marbles encasing squares of the system flat glass. I then chopped 'em in half ground 'em, and no splitting has shown up in a month. Which is good enough for me, but I guess I should take it up the hill and see what a polariscope has to shoe.
This is all a random collection of system flat glass I'm testing, with no batch # or date. So I guess any results I arrive at aren't scholastic.
I did meet Toso in Toledo briefly at Gathered glass. His mantra seemed to be "FUNDAMENTALS!"
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Last edited by Mike McCain; 01-12-2018 at 07:31 PM. Reason: I met Toso!
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Old 01-13-2018, 09:08 AM
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I am assuming you scored and tapped clean a vertical break on the ring.

While the ideal test would have equal amount of color and clear, I find that even with a great disparency, the ring will show gap or overlap quite clearly once you have done the vertical score. More importantly I suspect is that if you make the cup with the two glasses in question and then saw off a ring, if it survives the sawing , it is likely compatible, not always but the bulk of the time.
When I'm testing for a ring, I have the luxury of being able to gather both the color and the clear from pots so I can get greater volumes of the color if I need it.

The Hagy seal probably given you the greatest opportunity to get equal amounts of glass in both the clear and the color but without a good polarizing screen, it's difficult to really measure the retardation. The other thing about a hagy seal is that if there is substantial mismatch. the seal doesn't usually survive the process. Then you know it didn't fit, but not how much or in what direction.

The final irritation is that there's nothing you can do to change the expansions if it's commercial glass. I can mess with mine easily. Beware of pieces which don't check after you've made them. Variance in thicknesses yield a lot of opportunity for the work to break. If it were me, I'd make some work using the glasses in question in thick stock and then try to saw them.
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