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Tips, Techniques, and Questions -- Technical questions or tips

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Old 2015-03-12, 7:26am
paigeken2000 paigeken2000 is offline
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Join Date: Mar 12, 2015
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Default Newbie with two questions

Hi, brand new new new person here. Just starting to read up on this and took one class but VERY interested. I have two questions that weren't very clear to me:

1) I have a question about the glass and which you work with. I learned a little bit about the glasses having different coe numbers and that you cannot mix them very much unless they are close but I am wondering how you choose which type to work with.

Do most people work with all of them, or choose one they mostly work with. How do you choose? Is it how they handle? Because one has more color options? Simply a matter of taste after gaining some experience?

2) Regarding annealing your beads. I see that some people say for your home, you can use vermiculite beads but that they aren't officially annealed until they go in a kiln. So, if you don't have a kiln, how does that work? Do you fiber blanket or vermiculite your beads at home and then when you have a bunch, bring them to a kiln? Is that 'batch annealing"...can they wait that long? THANKS
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Old 2015-03-12, 8:47am
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FosterFire FosterFire is offline
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If they don't go into a kiln, then they are not annealed. Yes, you can batch anneal a pile of beads. They can wait days, months or years. There is a catch. The longer you wait, the more likely they are to crack. Once cracked, they are cracked forever.
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Old 2015-03-12, 8:55am
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Sheila D. Sheila D. is offline
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As far as the glass, the 2 most common are COE 104 and Borosilicate (mostly used for sculptural work. I would start with 104 if you want to make beads. Get a sample pack and jump in! You can put your newbie beads in a fiber blanket, but as you get better, you'll want to invest in a kiln.

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Old 2015-03-12, 9:58am
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Eileen Eileen is offline
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Also you can only use the blanket/vermiculite/annealing bubbles to cool your glass on fairly small beads so they will cool a little more evenly. Larger ones are much more likely to crack cooling that way.
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Old 2015-03-12, 10:22pm
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jhamilton117 jhamilton117 is offline
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You can do pretty much anythingwith any type of glass, they just have different carachteristics to workongs and strength. Boro/coe 33 is acid resesitant and very strong, its commonly used in pipes and scientific glass like beakers and test tubes. Boro takes a lot more heat but doesnt shock and break as easily while working.
What coe you want to use really comes down to what you wanna make, you can make beads with boro but its not as easy of soft glass. Cant make good or safe pipes out of soft glass. Ornaments and pendants, small scuplture, etc. can be done in all COE's
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Old 2015-03-13, 12:03am
snoopdog6502 snoopdog6502 is offline
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I work boro, pendants, marbles,jars and few pipes, some sculpture, I have a kiln and have tossed my stuff on a concrete floors to prove its tough and annealed.
Its good glass for sure.

No matter what you make it not finished till its annealed so a kiln helps make a studio complete.
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Old 2015-03-13, 8:34am
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Speedslug Speedslug is offline
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I started with soft glass (coe 104) because that was what was suggested by my first teacher. It is sometimes referred to as Italian glass because that is where the formula for it originated.

Then I looked at the costs of glass and found that coe 104 was the less expensive of the choices as well.

There is softer glass, called saktake at around coe 113 to 120 and it tends to be most popular in Japan.

The glass I tend to call medium soft is often used in stained glass window work and I think it is used in the 'hot shops' that do glass blowing with big half pound gathers of molten glass on the blow pipes.
"Spectrum" is a name that comes to mind and I believe it has a coe of 96 and / or 90.
A lot of the frit used in bead work comes in that range and can be used in very small amounts on the outer surface of some beads made with coe 104 glass.

The boro glass with a coe of 33 was developed to withstand the heat changes and was used at first as a standard glass in scientific work. The classic black and white movies with the bubbling beakers and fuming test tubes of the mad scientist comes to mind.
It also is used in the kitchen these days and there used to be a brand name of Pyrex although I think that company has been bought up.

The coe that everyone talks about is short for coefficient of expansion and that has to do with the way different types of glass act when they are heated to the melting point.
Soft glass gets a lot larger in volume than boro glass at those high temperatures and that means that it moves more when it cools and shrinks.
Because glass does not conduct heat very well the outside will cool off much faster than the inside and the out side will shrink and press inward on the hot glass on the inside. As the inside starts to cool off it will try to shrink also but it cant because the outside has cooled and stopped moving.
This creates stress in the structure of the solid glass and if the stress is too large the glass will crack eventually, sometimes with a huge amount of force. Look up a youtube video of "Prince Rupert's Drop".

But if the glass is cooled slowly enough from its molten state through a critical temperature called the strain point, the internal stress can balance out and the stress will equalize before it solidifies. Glass can also be reheated up above the strain point and can then be cooled slowly to reduce this stress.

Cooling the glass slowly like that is called annealing.
And that is why a lot of us say the glass is not finished until it has been annealed.
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Last edited by Speedslug; 2015-03-13 at 8:39am.
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Old 2015-03-13, 9:14am
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AmorphousDesigns AmorphousDesigns is offline
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this is my own opinion, which others may not share, but FWIW:

Soft (104 COE) is popular for beads:
  • huge color palette
  • relatively low cost compared to boro
  • relatively lower heat required to melt compared to boro. This also has implications on what kind of equipment you need, as well as your personal tolerance for heat on your own skin (much less radiated heat on your hands, chest and face).
  • longer working time (stays molten longer to give more time to shape the glass into chosen form)

Boro (33 COE) is popular for sculpture and functional (pipes):
  • can tolerate a lot more thermal stress before cracking than soft, so it's easier to create a larger sculptural piece
  • for reason above, it's easier to work hollow forms with boro
  • many available "Striking" colors which can give a very unique look based on how it's worked

many people work with both (or more COE's), but you MUST be careful about keeping them separate and well labeled. It can be impossible to tell what glass is what or even distinguish between certain colors if they have no labels. There are many stories of someone picking up the wrong rod and accidentally mixing COE's, which seems fine when everything is molten, but cracks to splinters after it cools down. So the moral of the story is: if you have multiple COE's in your workspace, you have a higher risk of mixing them accidentally and must take precautions to prevent such from happening (like only working with only one COE at a time and clearing the bench before switching, labeling religiously, etc).

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Last edited by AmorphousDesigns; 2015-03-13 at 9:21am.
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