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Christense Agate Seam Survey Results


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I just interviewed 198 striped opaques and 86 guineas and asked them where their seams were located. The choices for answers were 1) very close together 30 degrees , 2) somewhat close together 120 degrees and 3) opposite each other 180 degrees 4) only one seam.

Striped opaques Guineas

30 degree 5 % 5 %

60 degree 12 % 9 %

180 degree 68 % 50 %

only one seam 15 % 36 %

What the conclusions of the survey are I have no idea except to say that if seams are the result of the cutter's action when it goes across the stream of glass, why are there so many CA's with only one seam ?

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Exactly! I am not convinced the seams show up just because of the shear. Not including hand gathered,etc,but most all machine made marbles went through a shear of some type. I have some thoughts but still getting some confrimed. Why do most of the WV swirls and some others normaly have no seams easily visiable??? Yes,they had to have cuts,but why are they hidden more than,Vitro,CAC,Akro,MK,Peltier,etc. Why do some CAC and a few others have only one seam showing? I always thought even as a child that these straight lines on or across a round marble looked out of place or distracted some from the looks. Do the seams show up in the finished marble because of equipment misalignment,temp,the configuration inside the main tank,glass type,type of shear,shear blade width,etc,. I know some of the above has an affect on shear marks or cut lines appearng. Griff and i do know some things that can affect cut lines or shear marks. We made some single seam and some double seam Jabos one night during the Tribute to Friendship run. If the older larger companies could control the seams,cut line marks showing on a marble. Then why did they not eliminate them?

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I've wondered about all that for a while . . . I have no real contribution to make, except to say that I always thought of the CAC one-seamers as a product of timing, whether intentional or not -- that maybe the timing (and/or temperature?) was such that the bottom cut-off seam curled over back into the body of the marble before the second cut was made. That might also (theoretically) explain some of those seams-really-close-together CAC two-seamers . . . kind of a "blurp" thing! As to knowing how to eliminate the seams - - - maybe they did, but didn't care to. The makers just liked the effect? The seams are certainly diagnostic for CAC machine-made slags . . .

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Well I interviewed a slightly smaller population, but due to complaints from the striped transparents about being left out I included them. Total was 70 striped opaques, eight guineas and or cobras, and four striped trans.

total # 82

single seam 25 30%

30 degree 11 14%

60 degree 12 15%

180 degree 29 35%

Have no Idea what it means I didn't select for seam style mainly eye appeal and a few came in groups.


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I still get a feeling when looking close at many single seam CACs(not all) that they are not one seam on top of another but actually may be some type of handgathered marble. Just a thought.

But it's an interesting thought . . . I don't think I've seen enough to comment any more than that, but I sure will start looking more closely at any single seam ones I run across. Thanks . . .

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Seriously, I don't have the best eye for this sort of thing. Some people see a seam where I don't. I suppose maybe there is a tail on some seamed CA's but I sure don't see a tail on any single seamed examples of mine. Lots of people see evidence of hand gathering when I don't either. That's just my "eye" I guess.

No, I did not look at CA slags. Those boxes are in my safe deposit box.

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  • 2 weeks later...

I was a little bored,and beat up from snow shoveling,so Ill put a little something to this.

Just off of the top of my head,,,,,

With the exception of "hand gathered",All machine made marbles have 2 cut lines.Im not talking about an illusion of being a cut line,but an actual,shear marks.

The tricky part is if the shear mark is rolled,inside the marble,where it is no longer visable,in an opaque marble.

This is controled by many factors,with the most influence coming from the lower shear plate,and the flow.

In the lower shear plate,there are 2 "holes",and this shear plate moves back and forth,cutting off the "marble blanks".To give you a visual,picture a small piece of glass,shaped like a tootsie roll.

Between the 2 holes in the bottom shear plate,there is a span of steal,that the glass is dragged across,for less than a second.This dragging action,is one of the controlling facters,of the placement,of the shear marks.The wider the steal is,between the 2 lower shear holes,= more drag,and with more drag,the seams are,"bent",closer together.

For a visual,take the tootsie roll,and bend it.

Thats just the beginng,of things that can influencs it.

There many other things to consider.The temp.of the glass,higher temp= faster flow,gives you a lttle more "stacking" on top of the shear.

Distance the glass blank tavels,before landing on the rollers.

The diameter of the rollers,

The radius of the "threads" on the rollers,

The raidius of the holes in the lower shear plate,

The diameter of the upper shear plate,

The location of the shear,relative to the center of the glass stream,

The distance the glass stream travels,before entering the shear,

The speed of the shear,,

and on and on and on,,,,,,,,

Shorten the stream,and put a shear plate,with a gap of an 1/8 inch,instead of 1/4 to 1/2,might yield a 2 seam,striped opaque,,,,,,,,,,,,,,,,at jabo,,,,,,,,,,

sorry,got side tracked!!!--------LOL


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And just imagine there were a lot more feeding and shearing setups than the type Griff describes. Many had what looked like an actual pair of scissor blades as shears. And on some the glass stream actual traveled over rollers before being sheared. There was an amazing ammount of setups. I just wish someone had the diagrams to show us, as to what the CAC setups(there were several) were like.

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Yes! to all that, Griff & Galen. The "drag" on the shear in particular describes what I was trying to express -- thanks.

Also, as to one or more seams disappearing into the interior, these are sometimes visible in Peltier slags . . . nothing at all on the surface to indicate a shear mark, but inside you can sometimes see the straight "clip" of the internal white.

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Id love to see the prints on all,or any the machines,and hands on,in operation,would be a dream!!!!!

20 year machinest makes the wheels turn,when looking at these things.

Ive only fingerprinted,peltier,and alox.Just a little observation time,and some hands on at jabo,,,,,,,,since 96.


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