Mixing Coe's

BrownGirl · #1 2011-08-16, 2:06pm

I love Chalcedony and Raku. I recently bought a 1/4# of Chalcedony from Gaffer and did not realize it was 96 Coe. It's the only non 104 Coe glass I have.

Last night I was reading one of my books on encasing and it said that you can safely encase 96 Coe with 104 Coe. I had never heard that before and was wondering if that is in fact safe to do. The book said you cannot encase a higher Coe with a lower Coe but encasing a lower Coe with a higher Coe is okay.

I don't think the book would give me bad information on perpose so, I feel okay trying it out but, I just wanted to check in and see what some of the more seasoned lampworkers have done and what are some tips and tricks for doing this successfully?

Thanks!

--Monica

jamie lynne · #2 2011-08-16, 3:05pm

I think you may have mis read that. I bet it says you can usually get away with encasing small amounts of 96coe glass (think sparse amount of frit) on a 104 base and encase with 104 glass. If you encase a 96 bead with 104 you will get a big ol' crack. Maybe not right away, but it will happen.

LarryC · #3 2011-08-16, 4:10pm

Quote:

Originally Posted by BrownGirl

I love Chalcedony and Raku. I recently bought a 1/4# of Chalcedony from Gaffer and did not realize it was 96 Coe. It's the only non 104 Coe glass I have.

Last night I was reading one of my books on encasing and it said that you can safely encase 96 Coe with 104 Coe. I had never heard that before and was wondering if that is in fact safe to do. The book said you cannot encase a higher Coe with a lower Coe but encasing a lower Coe with a higher Coe is okay.

I don't think the book would give me bad information on perpose so, I feel okay trying it out but, I just wanted to check in and see what some of the more seasoned lampworkers have done and what are some tips and tricks for doing this successfully?

Thanks!

--Monica

This is NOT true. There isnt a certainty that two different glasses of the same COE will be compatible. Mixing COEs in ANY way just makes it more likely that there will be residual stress in the finished product leading to failure. Mixing without testing is always bad practice. You may get away with it but then again you may not. Even if the finished piece does not immediately crack, it may crack a day, month, or years later. Most glassblowers who dont do any testing have experienced this at least once or twice. Books are not always correct.

BrownGirl · #4 2011-08-16, 4:23pm

I hope I am legally allowed to quote a book I own. This is what it says:

"Mixing COE's

A high COE base glass accepts minute quantities of a lower COE sprinkled across the surface. Lower COE glasses can be encased with higher COE glasses, as long as the surrounding encasing is used in large quantity. The higher COE glass contains the stress created between the two glasses with compression forces. As the gulf between the COE's widens, this no longer holds true because the stress is too great."

Deanna Griffin Dove, encase it!

This is really saying that you can encase just the frit then that is on the higher COE base? Okay. I guess I got excited and took only what I wanted out of it. *laughs* Shocker.

Thanks for the clarification.

Elizabeth Beads · #5 2011-08-16, 5:10pm

That said, many people use Raku and Chalcedony to make twisties with 104 CoE glass and use it on the surface of a 104 CoE base.

You can get beautiful effects encasing Raku and Chalcedony -- just use a 96 CoE clear such as Uroboros or Gaffer (my personal favorite).

purpledragonfly · #6 2011-08-16, 5:14pm

I think a general rule of thumb is to never mix more than 25% ( I believe ) of your bead amount with a different COE......at least that is what I have always been told.

alb6094 · #7 2011-08-16, 5:52pm

I constantly encase. That said, I still have beads hanging around that were 104 clear, then 104 black, then chalcedony or raku, then thick encasing.

However over time (6 months to a year) I've found that I have about a 60% rate of failure with these beads. It was my own experiment prior to selling and my results convinced me that if I want to encase frit and be *sure* the bead will last I needed 96 COE so in the end that's what I've done, switched COEs for those beads that contain frit.

It's entirely possible the failures were kiln temp variances, different garaging experiments, or admiring the bead too long before popping it in the kiln. It was an experiment that was part of my learning process as a beadmaker. Your mileage may vary widely from mine, this was just my own personal conclusion for my own piece of mind.

I've also found I'm quite fond of the 96 palette as a byproduct. *sigh* Oh well......

Quote:

Originally Posted by BrownGirl

I hope I am legally allowed to quote a book I own. This is what it says:

"Mixing COE's

A high COE base glass accepts minute quantities of a lower COE sprinkled across the surface. Lower COE glasses can be encased with higher COE glasses, as long as the surrounding encasing is used in large quantity. The higher COE glass contains the stress created between the two glasses with compression forces. As the gulf between the COE's widens, this no longer holds true because the stress is too great."

Deanna Griffin Dove, encase it!

This is really saying that you can encase just the frit then that is on the higher COE base? Okay. I guess I got excited and took only what I wanted out of it. *laughs* Shocker.

Thanks for the clarification.

LarryC · #8 2011-08-16, 9:04pm

Quote:

Originally Posted by purpledragonfly

I think a general rule of thumb is to never mix more than 25% ( I believe ) of your bead amount with a different COE......at least that is what I have always been told.

Does this make sense to you?

LarryC · #9 2011-08-16, 9:07pm

Quote:

Originally Posted by alb6094

I constantly encase. That said, I still have beads hanging around that were 104 clear, then 104 black, then chalcedony or raku, then thick encasing.

However over time (6 months to a year) I've found that I have about a 60% rate of failure with these beads. It was my own experiment prior to selling and my results convinced me that if I want to encase frit and be *sure* the bead will last I needed 96 COE so in the end that's what I've done, switched COEs for those beads that contain frit.

It's entirely possible the failures were kiln temp variances, different garaging experiments, or admiring the bead too long before popping it in the kiln. It was an experiment that was part of my learning process as a beadmaker. Your mileage may vary widely from mine, this was just my own personal conclusion for my own piece of mind.

I've also found I'm quite fond of the 96 palette as a byproduct. *sigh* Oh well......

Unfortunately a 60% failure rate is huge. The other 40% will most likely fail over time. Most likely was due to compatibility issues based on what you have described.

LarryC · #10 2011-08-16, 9:14pm

Quote:

Originally Posted by BrownGirl

I hope I am legally allowed to quote a book I own. This is what it says:

"Mixing COE's

A high COE base glass accepts minute quantities of a lower COE sprinkled across the surface. Lower COE glasses can be encased with higher COE glasses, as long as the surrounding encasing is used in large quantity. The higher COE glass contains the stress created between the two glasses with compression forces. As the gulf between the COE's widens, this no longer holds true because the stress is too great."

Deanna Griffin Dove, encase it!

This is really saying that you can encase just the frit then that is on the higher COE base? Okay. I guess I got excited and took only what I wanted out of it. *laughs* Shocker.

Thanks for the clarification.

Not sure what the point of this passage is at all. Wish there was some magic recipe that would allow you to mix dissimilar glasses without testing but there is not.

MelanieG · #11 2011-08-16, 9:20pm

Every bead I have ever made with 96 Coe frit and 104 Coe glass has cracked. I will concede that a lot of factors can contribute to cracking and that it's possible that I just didn't do it right but I can't think of a good reason to try it again when there are so many other ways to spend my time at the torch

I have friends that think I am just being stubborn and stupid about it but for me there are enough incompatibilities within the 104 Coe line that I am not interested in introducing more on purpose.

BrownGirl · #12 2011-08-16, 9:52pm

Quote:

Originally Posted by LarryC

Not sure what the point of this passage is at all. Wish there was some magic recipe that would allow you to mix dissimilar glasses without testing but there is not.

Not sure what the point is at all? Hmmm. Well, I was showing you what I read and how the wording confused me. Sorry I wasn't more specific.

Lisi · #13 2011-08-16, 9:58pm

I use only frit size #0 or #00 on 104 COE and I never encase any beads with frit. I have countless frit beads of all kinds from my newbie days that are 8-9 years old and they are still intact. Trick is, I only use the small size frit and never the #1 or #2.

There is only one set of beads that I make that used size #1 on 104 and I've never had a problem with them and have sold too many sets to count. Those were tested for years but after just those beads passing the test, I still never wanted to chance it with any other combo of #1 frit on 104.

I use size #1 frit on Uroboros only, and on Bullseye, only a thin layer of #0 or #00 and it works out well. Bullseye is even worse with frit than 104, so test them out before selling, and of course never batch anneal Bullseye anyway because you're asking for a disaster. Frit or not.

alb6094 · #14 2011-08-17, 12:24am

Quote:

Originally Posted by LarryC

Unfortunately a 60% failure rate is huge. The other 40% will most likely fail over time. Most likely was due to compatibility issues based on what you have described.

I think so too Larry, that's why those have never left the studio. I just don't do much frit work that's not encased so for me it was necessary to switch to 96 for beads containing frit.

PerfectDeb · #15 2011-08-17, 12:24am

I've never heard that and I'm really surprised that's actually in a book - you have absolutely no control over the outcome and the bead could crack a year later

BrownGirl · #16 2011-08-17, 12:35am

Quote:

Originally Posted by PerfectDeb

I've never heard that and I'm really surprised that's actually in a book - you have absolutely no control over the outcome and the bead could crack a year later

I keep re-reading that passage and... It does sound like she is saying it's okay to encase lower Coe with higher Coe and not just Frits. That's why I asked because it really did confuse me. And I am 100% positive I typed it correctly.

PerfectDeb · #17 2011-08-17, 12:39am

No I believe you - I just think it's flawed advice especially for a beginner

Lisi · #18 2011-08-17, 12:58am

Somewhere a looong time ago I read something that a "famous" marble and paperweight maker said about furnace glass frits and using a very small amount of a color on flower petals in making paperweights. Something about how such a tiny amount beneath the heavy glass layer is okay and how it would be compatible. Yep a famous glass artist wrote that, I forget who it was but it's someone very well known in the glass world.

Elizabeth Beads · #19 2011-08-17, 6:32am

I have made hundreds (possibly thousands) of frit beads using the "96" blends and solid colors in size 1 on both 104 and on Bullseye. I make typical donut shaped beads and I don't encase them.

I don't think I have ever had one crack - and I've dropped some on the tile floor. I dropped a whole set I was stringing recently (lost hold of the end and they went a-flying) - all were fine.

I've used up a boatload of scummy 104 clear as a base for frit beads and also used the ASK clear that wasn't compatible with anything as a base for frit beads. I've used silver foil with frit on 104 quite a lot too. No problems.

I garage anneal at 930 and soak for 1.5 hours, then another 45 minutes at 840 with a slow cool down in a firebrick kiln.

I've had wonky ones, disastrous color combinations (I've given up on yellows and most greens as a base) and a few that got contaminated with bead release, etc. I just washed a jar of frit that I bought in the Garage Sale that had some crud in it (rinsed it in a tea strainer and dried it on a paper towel). I'll see how that worked out today.

LarryC · #20 2011-08-17, 6:38am

Quote:

Originally Posted by BrownGirl

Not sure what the point is at all? Hmmm. Well, I was showing you what I read and how the wording confused me. Sorry I wasn't more specific.

Sorry. Didnt mean that I didnt understand you

I meant the passage in the book doesn't make sense.

Eileen · #21 2011-08-17, 7:16am

I asked some questions about this a while back, and people put some good links in their replies. They also talk about the difference in 96 furnace glass, and frit being made from that. I hope this is useful.

http://www.lampworketc.com/forums/sh...81#post3575081

Griffin Dove · #22 2011-08-25, 11:20am

I've made a graphic to clear things up. Hope it helps. Unfortunately, the passage is general, concise, and meant as an overview, because of huge variables in colors and glass. Deanna

EchoTantuli · #23 2011-08-25, 2:04pm

I think I heard it was more like 15% for surface only although I have encased some that have worked out fine. I think as Larry said you would just have to test them out. I have had beads crack that were the same COE sometimes.
I really like silver glass over Gelly Sty and encased but all of them have cracked and were supposed to be compatible.
-Echo

LarryC · #24 2011-08-25, 2:52pm

Quote:

Originally Posted by EchoTantuli

I have had beads crack that were the same COE sometimes.
I really like silver glass over Gelly Sty and encased but all of them have cracked and were supposed to be compatible.
-Echo

There is a tolerance that definitely varies by manufacturer for the stated COE of a particular glass, lot to lot there must be some manufacturing variation, and as your are working the glass the physical properties do change so this is not surprising. Additionally, other than COE, there are other factors that effect fit between two dissimilar glasses as well. Lots of variables here.

RyanTheNumberImp · #25 2011-08-25, 3:54pm

There are no hard rules but as you gain experience you might learn how far you can push the glass.
Chris buzzini's paperweights are made with 96 color and 108 clear:

Needless to say, there is zero chance of them cracking.

COE isn't the only factor when mixing glass and neither is quantity. Shape and the properties of the individual glass also comes into play.

Thermal expansion is non-linear so coe is a very rough description of how the glass behaves. Various colors may also have different strain points. Finally, some extremely dense colors tend to be more pliable and don't crack as easily.

To make things ever worse, when glass reacts you have no guarantee that the COE isn't changing.