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Tips, Techniques, and Questions -- Technical questions or tips |
2008-09-22, 5:12pm
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Lover of Life
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Simple stupid question about annealing
Hi. Yes, it's most likely a stupid question, but I am still a beginner, so...
Since I've started in March, I always batch anneal, for a few different reasons. I also read that it is not inferior to garage annealing. Very recently, I learned how to make blown vessels, and I am having a blast!!! Unfortunately, over half of them have cracked, a couple at the top of the body, but most along the lip/neck. I've never had such bad luck with beads.
If I shoot these straight into the kiln after making them, should this eliminate the problem?
TIA,
Becky
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2008-09-22, 5:27pm
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Ass-kicking Cephalopod
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yes, as long as you have them evenly heated. The reason they are cracking at the lip/neck is probably because of the difference in thickness of the glass causes the cooling to be uneven.
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2008-09-22, 6:02pm
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Curmudgeon
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Quote:
Originally Posted by bexrox
Hi. Yes, it's most likely a stupid question, but I am still a beginner, so...
Since I've started in March, I always batch anneal, for a few different reasons. I also read that it is not inferior to garage annealing. Very recently, I learned how to make blown vessels, and I am having a blast!!! Unfortunately, over half of them have cracked, a couple at the top of the body, but most along the lip/neck. I've never had such bad luck with beads.
If I shoot these straight into the kiln after making them, should this eliminate the problem?
TIA,
Becky
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If they are cracking before kiln loading, putting them directly into the kiln to soak at 1100 would reduce the problem.
If they aren't cracking before loading into the kiln, but cracking during anneallng, it's thermal shock caused by the thinner parts being too different a temperature then the thicker parts. You need to reduce the ramp speed to allow the glass to heat more uniformly.
It's usual to program a ramp speed to allow for the thickest glass, but when there's a substantial difference in thickness in a single piece of glass, it's necessary to ramp even slower to compensate for that difference.
When ramping glass that has significant difference in thickness, it's a good guideline to ramp at half the average ramp speed for the different thicknesses. For example, if the ramp speed for the thickest part of your glass calls for a ramp speed of 400 dph and the ramp speed for the thickest will permit ramping at 600 dph, you should ramp at 250 dph (half of the 500 average).
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Dennis Brady
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2008-09-22, 9:25pm
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Senior Member
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Yes
(you might have better luck with vermiculite too--if you're using a fiber blanket now--it's a little better at "packing" around the weird-shaped stuff that you're trying to batch later--but odd shaped stuff & things with protrusions & lots of decorations, or lots of mixed glasses tend to do better if you pop them right in a kiln--it's REALLY hard to get a good even heat in them & then get them into vermiculite or a blanket "just right" & then to a kiln later for batching without ending up with cracks. Round/tab/basic shapes are just easier for that)
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2008-09-22, 9:46pm
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Ass-kicking Cephalopod
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1100 degrees is too hot for most soft glass - I would not put it into a kiln that hot. I would shoot for a normal annealing temp of around 960 or so.
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2008-09-22, 11:39pm
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Curmudgeon
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Quote:
Originally Posted by squid
1100 degrees is too hot for most soft glass - I would not put it into a kiln that hot. I would shoot for a normal annealing temp of around 960 or so.
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The 1100 soak is to ensure the glass is a uniform temperature to protect against thermal shock. It should then be dropped to 960 to anneal.
Thermal shock can occur when hot glass is put into a 960 temp kiln but not one at 1100.
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2008-09-23, 12:29am
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a pox upon an idiot :..
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Agreed that 1100 is too hot. If I feel the need to raise my garage temp while I'm working I never go higher than 980, and that's only for some Czech colors and I think two of the CIM's, (Peacock Green and Halong?).
Try evenly heating the vessel slowly an then give the mandrels a good shot of heat on both sides so it runs along the mandrel. Honestly though you need to go directly into a kiln if you want to solve the problem.
If you do decide to purchase a kiln, MAKE SURE you search all the threads for information on reputable sellers, especially the Family Room as it seems to be the place where the largest amount of people post their good and BAD experiences.
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2008-09-23, 3:52am
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BeadsonCypress
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When I use 1100 degrees I get "flat spots" on the bottom///
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2008-09-23, 5:23am
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Ellyloo-YAH!
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I have the kiln at 960-980, and I'e never had thermal shock problems. you'd have to have them pretty cooled off to cause that.
1100 would be the right temp for boro...
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2008-09-23, 5:43am
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tinkmartin.etsy.com
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Try to get your vessel as evenly heated as possible in the flame, then go directly into the kiln.
Higher kiln temps are a real problem for small-scale blown works: You will get flat spots, as Susan mentioned. A higher temp isn't the solution: Making sure you get even heat throughout the piece is. By doing a nice, slow, even heat at the torch, then making sure you soak long enough at your "hold" temp in the kiln, you should eliminate the breakage.
In my classes, I liken it to toasting marshmallows. You can set the marshmallow on fire (higher heat) and actually burn the outside, but you'll still end up with a solid, cold lump of marshmallow inside. (Risk of thermal shock)
By heating more slowly, and with time and care, you'll get a nice toasty brown on the outside and the center will be equally heated through. (Minimal risk of thermal shock)
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2008-09-23, 7:53am
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KILN BUILDIN FOOL
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Quote:
Originally Posted by Tink
Try to get your vessel as evenly heated as possible in the flame, then go directly into the kiln.
Higher kiln temps are a real problem for small-scale blown works: You will get flat spots, as Susan mentioned. A higher temp isn't the solution: Making sure you get even heat throughout the piece is. By doing a nice, slow, even heat at the torch, then making sure you soak long enough at your "hold" temp in the kiln, you should eliminate the breakage.
In my classes, I liken it to toasting marshmallows. You can set the marshmallow on fire (higher heat) and actually burn the outside, but you'll still end up with a solid, cold lump of marshmallow inside. (Risk of thermal shock)
By heating more slowly, and with time and care, you'll get a nice toasty brown on the outside and the center will be equally heated through. (Minimal risk of thermal shock)
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Thanks Tink, Now I need toasted marshmallows
1100 Huh, me see flat spots in you future.
Mike
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2008-09-23, 8:22am
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Pyromaniac
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I'm having S'mores this weekend and my supper club out in the country!
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2008-09-23, 8:50am
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Lover of Life
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Thanks everyone. I was a little surprised by the 1100 suggestion. That is where I set my alarm to check on my 6mm thick slumping bullseye. Sometimes the process is well on its way by then.
Most of the vessels I've been doing are 96 COE so I can coat them with my 96 frit. What would be an appropriate annealing temp (straight from the torch) and soak time for this? As I was searching for an answer to this question, I've read in a few places that 96 has more stress problems than 104. Can anyone verify this? Maybe I just shouldn't use 96 for vessels, but then I'd have to make 104 frit if I wanted to make them in this style (they are really cute!)... OMG, I'm so confused!
Becky
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2008-09-23, 9:38am
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Ass-kicking Cephalopod
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I have not heard that 96 has more stress. I would use your normal annealing temp - 960 to 970 should be fine. If anyone knows something different, please post more info!
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2008-09-23, 1:14pm
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Lover of Life
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Thanks for all the help, everyone. I have my kiln set at 970, which seems to be the average of everyone's suggestions. I never know when the vessel is heated evenly. I'm scared of remelting parts that are already nicely formed. I guess that's all about PPP.
Okay, I'm going in!
Becky
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2008-09-23, 1:59pm
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Curmudgeon
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Quote:
Originally Posted by squid
I have not heard that 96 has more stress. I would use your normal annealing temp - 960 to 970 should be fine. If anyone knows something different, please post more info!
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I would expect that because 96 is made to a higher production consistency then 90 or 104, it would have less rather than more stress. I would expect that the only time there would be an increase in stress would be when different COE glass was mixed with it.
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2008-09-23, 2:25pm
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boro color bender
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I would suspect any advise from somebody suggesting soft glass going into a kiln at 1100... might want to make some vessels and try your theory before telling people to do it with their work Dennis... unless passing on advise that will ruin somebodies work is acceptable to you.
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2008-09-23, 2:58pm
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DSDWC
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I garage at 906 and hold work all day at this temp.
At the end of the day I ramp up to 958 and the run through a standard annealing cycle for 104 glass.
I find that with pieces like large flat tabs, thin wall vessels, and any other shape that is susceptible to slumping in the kiln that the higher temps for holding work, especially all day, can cause you to have unacceptable glass flow ruining the work.
I would never put any soft glass into a kiln at 1100 degrees.
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2008-09-23, 3:09pm
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Ass-kicking Cephalopod
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Quote:
Originally Posted by Dennis Brady
I would expect that because 96 is made to a higher production consistency then 90 or 104, it would have less rather than more stress. I would expect that the only time there would be an increase in stress would be when different COE glass was mixed with it.
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The stress of manufacturing would be moot once it was melted and made into a bead. I also don't buy your statement about higher production consistency either - considering the source and all.
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2008-09-23, 3:10pm
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Ass-kicking Cephalopod
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Quote:
Originally Posted by Mr. Smiley
I would suspect any advise from somebody suggesting soft glass going into a kiln at 1100... might want to make some vessels and try your theory before telling people to do it with their work Dennis... unless passing on advise that will ruin somebodies work is acceptable to you.
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zackly.
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2008-09-23, 7:05pm
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Senior Member
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I know there's *lots* of different views on the COE mixing/matching of frits with glass of different COEs, but if you're only using a bit on the outside of the vessel, & you're using 96COE furnace glass (leaded) frits, you should be able to use 104COE glass with that without a whole lot of issues. (If you search for frit info in here, you'll find lots of info, explanations, etc. Some swear against it, but many others do it, and it's been explained quite well *why* & *how* it works scientifically to where I personally feel comfortable with it--it's a personal choice . Prairieson's posts have the best info in them!)
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2008-09-23, 9:01pm
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Lover of Life
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I use 96 on 104 with beads, but I was hesitant with vessels just due to the thickness of the walls, and that I really give 'em a good roll about in the frit. Much more than 20% on the body of the vessel, I'm sure.
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2008-09-23, 10:53pm
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one day at a time
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I've always found that 90 COE stresses when cooling after leaving the flame faster than 104, by a long shot. Bullseye has to be put in the kiln glowing more so than Effetre for instance.
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2008-09-24, 2:27pm
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Lover of Life
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Well, I managed to get two of them done yesterday, both 96, both straight in the kiln at 970, and I think we're good to go. Thanks for all the help!
Becky
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2008-09-25, 4:43am
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boro color bender
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Awesome!
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