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Tips, Techniques, and Questions -- Technical questions or tips |
2010-01-01, 7:07pm
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Hot Glass Neophyte
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Join Date: Aug 06, 2009
Location: Mt. Pleasant, SC
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Talk About Cracking
Hello Everyone,
Is it possible to tell what the different types of cracking are caused by? For example, cracks circling a bead versus cracks running the length of a mandrel?
What different things cause them? And would anyone care to discuss them and how to avoid them and repair them?
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2010-01-01, 7:18pm
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Glassy Broad :-)
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Hi Kristina! Happy New Year!
It's been my experience that cracks running the length of the mandrel are usually thermal cracks. We usually know how to cure that one eh?
The ones that go round and round, or are multiple are from glass incompatibility. I get those when I use the wrong clear over my silver glass. Hope this helps!
Nita
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2010-01-01, 7:24pm
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Hot Glass Neophyte
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Thank you! And can you discuss incompatibility within the same line of glass? Is it common?
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2010-01-01, 7:25pm
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Senior Member
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So the odd cracking is incompatability and the straight ones that crack the bead in half a thermal. (i.e. I spent too long looking at it before popping it in the kiln lol)?
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2010-01-01, 7:30pm
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Cracks from incompatibility can never be repaired. Even if you heat the bead up and make a repair it will eventually crack again.
Thermal cracks can be fixed by reheating the bead slowly up to about 100 degrees above the annealing temperature and bringing the bead back into the flame slowly. Then you can reheat, melt the crack closed and reanneal.
If you have already removed the bead from the mandrel before discovering the thermal crack then you will want to put bead release on your mandrel, then slde the bead on while the release is still wet. Clean any and all bead release from your bead before reheating it.
I hope that helps you.
As far as identifying types of cracks, sometimes it is really hard to tell, but basically cracks spider out from a central point - or many central points - are incompatibility. Cracks that run from one end of the mandrel to the other, as if the bead was going to break in half along the mandrel, are thermal cracks. However, his varies depending on the type of bead, round versus more sculptural, for instance.
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Pam
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2010-01-01, 7:35pm
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Hot Glass Neophyte
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Wonderful, thanks for the clarity and info!
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2010-01-01, 10:58pm
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He can do the origami
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Quote:
Originally Posted by Fine Folly Glassworks
Thank you! And can you discuss incompatibility within the same line of glass? Is it common?
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For the most part, the glass manufacturers strive to make their glass as close to a specific COE as they possibly can. They test their formulations prior to putting them on the market and as a general rule 33 COE glass is compatible with other 33 COE glass....... 104 COE is compatible with other 104 COE glass.
The reality of the situation is that most glasses are in a slight range of COE say..... 103 to 105 COE... just as an example. This can be further complicated by high amounts of silver in some glass, high amounts of say lead in other glass. The different viscosity at certain temperatures of different glasses can make a difference. This and MANY other factors can at times add up to incompatibility issues within "the same" COE.
There are some glass artists who have diligently worked hard at testing and posting lists of "incompatible" glass. This can be very helpful. However I strongly suggest that you personally experiment with these glasses and find out what will and will not work for you. There are some glasses that one person will always get cracks with and another person wont ever get cracks with. This has to do with everything from torch set up to torching styles to the way you cross your legs and the angle you hold your tongue while you are torching. Have a look at the vast amount of information out there but please experiment and you just may be surprised.
Otter
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2010-01-02, 5:45am
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Senior Member
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My best suggestion is to make test beads, small beads combining the glasses you want to use together before putting a lot of work into your beads.
Glass making is an art and compatibility issues arise when something is different in the making of the glass. It can be anything from a change in suppliers for colorants or exposure to a different environment than normal, or simply not precisely measuring the ingredients in the glass. Many glass manufacturers carefully test for compatibility before releasing their glass or sale, and others don't, so the best protection for you is to test yourself.
I wanted to add something about the cracking issue. If you case a bead you've made, incompatibility cracks can show up looking like thermal cracks. For instance, if you use glass A as the base bead and glass B to case, if there is incompatibility between the two, B will sometimes crack in a straight line to relieve the stress.
Nobody said working with glass was easy - lol!
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Pam
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2010-01-02, 7:55am
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I can see it is a wonderful and massive research project at times! Such a fascinating art.
And do you make up test beads to reflect CONTENT as well as glass (such as encased, pulled goldstone, and murrini)?
In this specific instance (below), I had an opaque core with a thin transparent casing, then I ran goldstone stringers like tendrils and placed murrini, THEN I encased the entire bead in clear and 'painted' a goldfish on the outer layer (all with the same 104 glass).
It cracked around the bead, indicating incompatibility between something in the mix... or poor handling in the assembly, right?
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2010-01-02, 8:40am
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Those look like incompatibility cracks. Strange because the colours you used don't usually have problems (in Effetre anyway) Were you using Effetre or some other type of glass? It would be helpful to know what clear you used as well.
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2010-01-02, 8:58am
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Quote:
Originally Posted by Carolyn M
Those look like incompatibility cracks. Strange because the colours you used don't usually have problems (in Effetre anyway) Were you using Effetre or some other type of glass? It would be helpful to know what clear you used as well.
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Thank you! All the glass (including the murrini and goldstone) were made with Devardi glass.
And here's the next question - I warmed the bead on the right with the circular cracks back up slowly, reheated it and healed the cracks, and then cooled it in my crockpot and it cracked top to bottom - in half. I don't have a bead kiln but I am getting successful beads with the crockpot and blanket method most of the time... see 2 others that didn't crack below.
Does the subsequent cracking in half say that the lampworker is the clear problem here?
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2010-01-02, 10:06am
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To me it looks as if the cracks come from the murini, as best I can tell from the pics. Not annealing beads of this complexity is probably not a good idea. Once you start adding and adding and adding, especially when the additions are not completely melted in, as in the murini, you are just setting yourself up for failure of the bead. It seems, thoiugh, that the murini is the problem glass and it does reflect incompatibility.
Just another thing to keep in mind, those beads cooled in the crock pot, etc., or any other way than with an annealing program in a kiln, have stress in them and more than likely will evenually crack. I made beads for five years before I even knew you had to have a kiln and I never annealed those beads. I put them in a large jar and each Jan. 1 I would take the jar down and remove those beads which had succombed to death by stress. Finally after 10 years there were no more beads in the jar. Stress does kill, and it can be slow or fast.
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2010-01-02, 1:41pm
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Hot Glass Neophyte
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Quote:
Originally Posted by pam
To me it looks as if the cracks come from the murini, as best I can tell from the pics. Not annealing beads of this complexity is probably not a good idea. Once you start adding and adding and adding, especially when the additions are not completely melted in, as in the murini, you are just setting yourself up for failure of the bead. It seems, thoiugh, that the murini is the problem glass and it does reflect incompatibility.
Just another thing to keep in mind, those beads cooled in the crock pot, etc., or any other way than with an annealing program in a kiln, have stress in them and more than likely will evenually crack. I made beads for five years before I even knew you had to have a kiln and I never annealed those beads. I put them in a large jar and each Jan. 1 I would take the jar down and remove those beads which had succombed to death by stress. Finally after 10 years there were no more beads in the jar. Stress does kill, and it can be slow or fast.
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Thank you. I do batch anneal in a large oval kiln for stained glass use, but I wait until I get a bunch of beads made up to do so.
May I ask what you suggest as an annealing schedule in this circumstance?
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2010-01-02, 2:01pm
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Unfortunately, with Devardi glass being so different from other glass, I would hate to advise you. I generally cool from the annealing temp at the rate of about 1 degree a minute until 400 degrees and then the kiln shuts off. I don't open the kiln until it's below 100 degrees. There are as many schedules as there are beadmakers. A couple of hints, don't turn your kiln off after a holding period and let it cool naturally. That is not annealing. The slower the annealing schedule the better. You can't over-anneal, but you can under-anneal. Does your kiln have a digital controler that allows you to ramp down?
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Pam
"It is easier to perceive error than to find truth, for the former lies on the surface and is easily seen, while the latter lies in the depth, where few are willing to search for it." Johann Wolfgang Von Goeth
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2010-01-02, 4:06pm
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Quote:
Originally Posted by pam
Does your kiln have a digital controler that allows you to ramp down?
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Yes, I can set it for whatever - up and down. What do you suggest as a base?
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2010-01-02, 4:13pm
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Lover of all things color
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My cracking is always along the mandrel vertically. And usually after I have cleaned the beads and they are laying out drying, sometimes the next day.
I can only assume that I'm just hot getting them hot enough before I put them in the kiln. I am very conscience of this issue and always try to give them a good soaking but sometimes it happens.
I clean my beads with a dremel and sometimes wonder if this causes the little stresses to start to form. I suppose it's better that they do this now rather than after they are sold but it's still frustrating to spend that much time on a bead and loose it.
When I first started I used the fiber blanket to cool and then did a batch anneal in my large fusing kiln. I found that I could do this with small to medium sized beads but the larger more complex ones just didn't survive the blanket cooling.
Here's what I did until I got the bead kiln. I had my fusing kiln running and the kevlar gloves handy, when I finished a bead I would put the gloves on and take the bead over to the fusing kiln, carefully lift the lid and drop the bead in on a fiber blanket to soak until I was done, at which time I started the program. Since you have a fusing kiln you might want to consider this if the kiln is close enough. Mine was about ten feet away.
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2010-01-02, 4:57pm
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Quote:
Originally Posted by Fine Folly Glassworks
Yes, I can set it for whatever - up and down. What do you suggest as a base?
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A lot depends on the size of your beads. I also don't know the annealing temp of your glass, but here is what I do for my beads. It is a conservative schedule, so - Once I close the kiln (I place my beads directly into the kiln from the torch) I hold at my annealing temp for one hour, but this can vary up to two hours depending on what I have in the kiln. After holding to make sure the beads are the same temp all the way through, then I start the annealing program. I have the controller programed lower the temp at 60 degrees an hour and it does that until off at 400 degrees. At 400 degrees the controller cuts off the kiln.
The few times I have reannealed on of my beads, I have brought it up to the annealing temp slowly, over a two hour period and then hold for an hour and start the annealing program.
As I said, this is my schedule. There are many less conservative schedules and some more conservative ones. You will have to decide what works for you. However, once again, this will do nothing for incompatibility cracks.
The whys of annealing are pretty simple: Make sure your beads are the same temperature from the center out before you start annealing your beads. The annealing process should allow your beads to cool slowly enough so that the outside of the bead is always the same temp as the inside of the bead. On sculptural beads the thin parts should cool at the same rate as the thick parts.
Stress is created in a bead when you mix glasses together or when you force a bead into a certain shape. (beads rounded in the flame have less stress than ones shaped in a press) That stress is relieved by slow cooling above the strain point of the glass. The strain point in most glasses is usually 100 to 150 degrees below the recommended annealing point. Below the strain point all stresses should be relieved and you cannot reintroduce stress into the bead. However the bead can still crack if the temp drops too fast, called thermal cracking.
Does this all make sense? If not, let me know.
Jan, it sounds as though your beads are cracking due to thermal issues. Cleaning the bead hole with a dremel will not cause your bead to crack along the mandrel unless the bead already has issues.
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Pam
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2010-01-02, 7:31pm
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Hot Glass Neophyte
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Thank you Pam and Jan. I really appreciate the annealing data and concepts.
My problem with putting beads into my kiln while hot is that it is the large oval Evenheat, at 41" wide, with a crank to raise and lower the lid. So I can't picture opening it hot and tossing a bead in onto fiberblanket... so I have been putting them into a hot crockpot and leaving them for several hours, then wrapping in a blanket to slow cool.
Do you have any better way to slow cool them before batch annealing, or recommend kiln procedures with my large oval?
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2010-01-02, 7:43pm
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When I am only going to make a few beads I use the Annealing bubbles. I find they cool the beads much more slowly and I don't have an issue with thermal shock as much as I did with fiber blanket. These beads are batch annealed within one week. Another good thing about the annealing bubbles is that there's no loose fibers being breathed in.
The annealing bubbles are available through artcoinc.com - they're a member here.
Hope this helps.
Suzanne
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2010-01-03, 2:01am
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i found i could batch anneal with smaller beads but anything bigger than say, 1/2" cracked down the mandrel
the cracks in the fish bead sounds like thermal to me
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2010-01-03, 8:22am
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Bead Release and Cleaning
Quote:
Originally Posted by pam
Stress is created in a bead when you mix glasses together or when you force a bead into a certain shape. (beads rounded in the flame have less stress than ones shaped in a press) That stress is relieved by slow cooling above the strain point of the glass. The strain point in most glasses is usually 100 to 150 degrees below the recommended annealing point. Below the strain point all stresses should be relieved and you cannot reintroduce stress into the bead. However the bead can still crack if the temp drops too fast, called thermal cracking.
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Thank you Pam, I have printed out your data as a reference. Would you please tell what bead release(s) you use and how you clean your beads, including what equipment you use?
If you use a Dremel diamond bit, where do you get them?
Deb & Suzanne, thanks much! I will look into the Annealing Bubbles!
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2010-01-03, 9:40am
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Bead release is a very personal thing, having to do more with your environment that lots of other things. I use Dip & Go Sludge and it works great here in South Florida. I also have about a thousand different kinds sitting on my desk that I have tried, but I always return to Sludge. It works for me and what I do and where I live.
I do use a dremel and in recent years have used the Art-In-The-Round diamond bit for it. I've used lots of kinds over the years, paying $1 each, or $5 or whatever, but Dave's diamond bit lasts a LONG time and really works great. It all depends, again, on what you actually need. I always cleaned my beads by hand at first, but gradually converted to the dremel which I already had, and it does make a very time-consuming job very fast and easy.
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Pam
"It is easier to perceive error than to find truth, for the former lies on the surface and is easily seen, while the latter lies in the depth, where few are willing to search for it." Johann Wolfgang Von Goeth
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2010-01-03, 12:58pm
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I second the dremel and a good quality diamond bit. Years ago when I would clean beads by hand I would much rather hit myself on the thumb with a hammer than sit and clean 50 or more beads at a time by hand. The dremel makes the job MUCH nicer.
Of course going totally off mandrel has solved the bead cleaning issue for me all together
Otter
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2010-01-03, 1:46pm
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Hot Glass Neophyte
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I am sold, but Art-In-The-Round's diamond bits are $29 each! Very steep for my pocket book. Are there any other suppliers that have a good product at a lower price?
I did just read that one person is going on 3-1/2 years of use, so I can understand the price better!
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2010-01-03, 3:09pm
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http://www.widgetsupply.com/page/WS/CTGY/bead-reamer and they are on sale for January!. I have had great luck with widget and, when I received some new bits that had bent tips, I took a photo and they replaced them with a nice apology letter.
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2010-01-03, 5:14pm
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Quote:
Originally Posted by tammydownunder
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Wonderful - thank you for the link! Do you recommend one set above another?
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2010-01-03, 5:35pm
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2010-01-03, 6:00pm
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I got my diamond files at Arrow Springs for something like $4.99. They fit into the Dremel, which for me is electric. I just ordered a battery powered one as it's safer to use around water. I haven't had any problems but electric shock is not something I want to add to my torching injuries...LOL
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2010-01-03, 6:49pm
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Quote:
Originally Posted by Fine Folly Glassworks
Wonderful - thank you for the link! Do you recommend one set above another?
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It totally depends on what size mandrels you are using
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2010-01-05, 7:48pm
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Does a bead have internal strain likely to crack it if left to long before annealing (I am talking about a bead that is not immediately garaged in a kiln, but is waiting to be batch annealed)?
If so, is there a minimum or safe amount of time to let beads sit before batch annealing?
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