Testing beads after batch annealing?

[sublimekate]

I just want to say in advance that I have been scouring the internet all weekend for an answer to this and I'm slightly the wiser but not entirely so any pointers, even if it's to an old thread on here would be welcome, but I think I've read all the annealing ones now ( REALLY)

OK my kiln has been playing up for the last two weeks, failing during batch anneal and garaging sessions at various stages, but predominatly during the hold segment on each occasion.

This means that all the beads I've made over the last two weeks are definatly not annealed, many have died along the way but some have survived. For the survivors my understanding, from what I read, is that even if I now anneal them there may still be potential stresses in the beads because they've been cooled very quickly from around 510/520c when the kiln has failed.

I understand (from posts by REDHOTSAL and some other websites I've found) that the ultimate test would be to do a polarisation test, I don't have any filters right now (i'm on with that) so can't perform the test, the other test would be the 'do or die' hot water test.

Stick with me, I'm getting to the question......honest.

So, the hot water test, is it: beads in fridge, beads in hot water? If so how hot, just out of the kettle, or hot tap water?

The reason I'm asking is this, I managed to successfully anneal my beads this afternoon, yes the bloody kiln decided to play nice, but because of my worries about the beads I did the fridge/hot water (out of the kettle) test on one bead from each batch that had failed, they ALL died within seconds of being in the hot water.

The interesting and very worrying thing is this, I have actually run two successful garaging sessions in the last two weeks since the kiln started playing up, and two of the beads I tested were from these sessions, but they cracked too, not just one crack, they both cracked in multiple places in different directions. I then tested two beads that were made and annealed before the kiln started playing up, they cracked too!

Does this mean that non of my beads are annealed properly, even when the kiln is completing successfully (according to the kiln!!), or would any bead struggle to survive the fridge/just boiled water test?

Also would any of you recommend testing all beads as a matter of course, or just one from each annealing run, or do some of you just take it as read that the beads are ok?

I'm sorry if this is a stupid question, but I honestly can't get to the bottom of it.

[Dragonfire Glass]

I have never tested my beads like that but as I drop them regularly (I'm clumsy) and they bounce quite happily on a tiled floor, I think they are ok.

[dangerousbead]

I'm no expert but I would've thought very few sorts of glass other than pyrex would survive that sort of treatment.
My beads are all failing because I've got my glass rods mixed up and I'm mixing different coe's, plus overzealous with incompatible frit. Optimism doesn't always pay off.

[garishglobes]

as I drop them regularly (I'm clumsy) and they bounce quite happily on a tiled floor, I think they are ok

Well, that makes 2 of us! I have to try and get to them before they skitter off under the stove

[Vicki]

Oh no Kate, I'm sorry all your hard work is ending up broken    Once i tried to get some stuck beads off the mandrel by taking them out of iced water & pouring boiling water on them & it didn't work, so I torched them off instead (gently at arms length ) so maybe your test does work...I think you don't trust your kiln & maybe it needs looking at even if just for your own peace of mind

[Chameleon]

I got some polarising film from HERE £1.19 and put it into little windows i made in a match box to make a polariscope (?) to check my beads. I randomly check them every now and then.

[saffie]

I got some polarising film from HERE £1.19 and put it into little windows i made in a match box to make a polariscope (?) to check my beads. I randomly check them every now and then.

How does that work Becky, do you just hold them up to the light and look at them through the polarising film? I am intrigued!!!

[Redhotsal]

http://www.frit-happens.co.uk/forum/index.php?topic=2057.0

The above link explains how to do the polarising test. I have included photos.

People have bought polarising filters from me for £5 per pair (including postage). I am currently out of stock but have placed a new order and am just waiting for them to arrive.

If you want order some from me just let me know here or PM me and I'll start sending them out as soon as I get them in.

Sal

[Hamilton Taylor]

"even if I now anneal them there may still be potential stresses in the beads because they've been cooled very quickly from around 510/520c when the kiln has failed."

With regard to annealing beads which have been thru' a 'failed' annealing cycle, and survived, you can just use a normal batch annealing cycle, and they will anneal just fine. There is no difference between the stress in these beads, and the stress in any other.
Immersing soft glass beads in boiling water will stress them a lot, and probably kill them, even if well annealed: the heat causes the surface glass to expand, but the deeper glass is insulated, so doesn't expand. Different expansion rates gives rise to huge stress, bead goes pop. The higher the coe, the greater the susceptibility to extreme temperature changes.

Use of polarising filters works great, as long as your beads are transparent. 

Personally, I figure that if they have been through a sensible annealing cycle, and they survive the vibration caused by cleaning with a dremel, they're annealed. The 'bouncing off a concrete floor' thing adds confidence, too...

Sean

[garishglobes]

I've just got a piece of polarising film from ebay - and realised that actually, the white on the computer screen acts great as a second film! So you can hold the bead between the film and the monitor - and voila!

[sublimekate]

Thanks everyone, been away for a few days but I've now cleaned the remaining beads with a dremmel, and I've been pretty rough with them, I'll bash 'em about a bit and see how they do.

I take it the boiling water test is 'overkill'

When I get the filters I'll make a habit of testing on a regular basis to put my mind at rest.

[garishglobes]

The 'bouncing off a concrete floor' thing adds confidence, too..

Presuming this provides concrete evidence?

[*rowanberry*]

Hmmm the freezer and hot water test still doesnt show up everything I am afraid. I tested Lauscha encasing on a pandora base, twas fine when they came out, then i placed them in a freezer overnight, then plunged them straight into boiling water. They were fine. However, 3 days later they cracked (due to the incompatability).
While that isnt an annealing issue but incompatability, it just shows you how the freezer/hotwater didnt how up the stress.
Oh yeh and they bounced on a floor too!

The polarising filter thing is ace though, put my mind to rest when I thought i was having a kiln issue (thank you Sal!).

[Hamilton Taylor]

Presuming this provides concrete evidence?

Given Claires experience, evidently not...

[Redhotsal]

I can't encase Lauscha over Pandora either.
It's interesting that you can see lines of stress in transparent beads even after they've been annealled if there are slight incompatibilities. e.g. if you put in loads of silver or mix lots of different glass together. You can anneal them as much as you like and at as many temperatures but these stress lines still show up because of the inherent differences in the components.
It's odd but after a time you get a "feel" for what's going to mix well with what. Even now I always hesitate to encase pastel pink beads if I can avoid it with Lauscha or Effetre as they seem to be inherently troublesome. For me, at least.