I am at a loss - cracking beads??

[Rachel_D]

I'm hoping someone may be able to shed some light on my cracking beads issue.

I've been making beads for 5 years so I'm fairly confident that I'm not doing anything different to what I've been doing.

I'll run through what's happened so far - all beads were placed in kiln straight away:

1. made 11 nugget beads with CIM kryptonite base encased with Vetrofond clear - every one of them cracked vertically down the mandrel line. I've used this combination before with no problems but assuming it was the CIM that was the culprit as I know CIM doesn't like to be encased.

2. nugget with CIM kryptonite encased in transparent light emerald - cracked down mandrel line - assuming again the CIM was the problem.

3. made 5 lentils with vetrofond clear swirled with Effetre turquoise, cobalt and a little nile green - 2 of them cracked down the mandrel line.

This seems like a thermal issue to me but I've checked the kiln schedule and nothing has changed.

So I did some more test beads -

4. Vetrofond clear swirled with a tiny amount of Effetre turquoise - a small vertical crack through the turquoise bit.

5. ivory nugget encased with Vetrofond clear - no cracks as yet.

So thinking maybe the kiln has a problem I thought I'd try cooling with vermiculite. Made several nuggets again with the kryptonite/clear - all cracked. Also made 2 nuggets with effetre turquoise swirled with Vetrofond clear - both cracked. Probably not a good test though as pressed beads don't do well in vermiculite.

I'm really at a loss now - I don't want to make anymore beads until I figure this out. I've got several beads that were in the kiln at the same time as the ones that cracked - they don't have cracks. But they're opaque so would I even see if they were cracked?!

Help!

[blong2001]

Have you checked your kiln temp with a different pyrometer? Maybe your kiln temp is off.
Best of luck!

[playswithfire104]

To me it sounds like the clear is the only thing they have in common. That could be the issue.

[MelanieG]

It's not accurate to say that CiM does not like to be encased. I have had a few problems with a few colours (Mink and Commando spring to mind) but have successfully encased Kryptonite. It's also not fair to blame the CiM or the Clear exclusively, since you're having cracking with all different glasses.

It does sound like you're having a kiln problem, since it is happening in all different beads using all different glasses. Are the cracks straight down the mandrel line, or are they jagged with a decided lean to one side of the mandrel or the other?

[Hayley]

Rachel - sorry that you are having cracking problem. Are they all pressed beads? You didn't indicate what type of bead for #4. Do you mind posting a picture of some of them? Have you tried making the exact same combination without pressing?

All glass manufacturers have a tolerance for their COE (e.g. +/- 2-3 COE points) . . . so if the glassed you use are at the far ends of the tolerance, you may run into very slight incompatibility issue especially on pressed beads. It also varies from batch to batch of the same color. Double Helix has a very informative write up about that on its website if you are interested.

Another suggestion is to send someone the glass you use and have him/her make some test beads using the exact combination.

[Rachel_D]

Thanks for the replies. I will try to get a pic of the beads a bit later.

Melanie - I agree - I've encased kryptonite before with no problems although this is a different batch so maybe that's why.

The cracks are all straight down the mandrel line both sides so it does definitely look thernal.

Hayley - bead 4 was a pressed nugget too. I'll try making some round beads using the same combination and see what happens.

I think I'll try adjusting my schedule and ramp down slower to see if that makes a difference.

I'll make some more beads tonight and see how they go.

I was thinking maybe I'm opening the bead door too much or for too long when I'm putting the bead and letting cold in.

I called someone who said they could take a look at my kiln next week so that's probably what I'll do next.

[Firebrand Beads]

It may simply be a matter of reheating the entire bead more thoroughly after pressing, before placing in the kiln. Remember what Jim Smircich says about "insurance heat"... sounds like you do need to even out the stress in the beads before annealing.

[Rachel_D]

Thanks Jenny. I made some more beads last night and I was pretty careful to make sure I heated them thoroughly and evenly but this morning I have 2 kryptonite and vetrofond clear nuggets, a round kryptonite/clear bead and 2 pale pink encased with vetro clear nuggets - all have cracked lengthways.

The nuggets are only 15mm ones so it's not that they're so big that evenly heating should be an issue.

I can't work out what has changed - either I've suddeny lost the ability to make beads or the kiln is out.

I must admit this has really made the self doubt kick in

[jjwiskus]

have you changed your bead release??? I had a problem a while back and it was becasue my bead release was to thin.
jeri

[Rachel_D]

Jeri - I wondered that too as I had been thinning my bead release because I was near the end of the bottle. But I got a new tub which I used yesterday and still had cracked beads.

[scaredycat]

Rachel, can you make something you've made before that is a similar shape but uses glass you have total confidence in? Given your experience and expertise I'd say either dodgy glass or dodgy kiln.

[scaredycat]

Another thought - the centigrade and fahrenheit haven't got muddled, have they?

[Carolyn M]

I would try changing the clear. Don't use any transparents, just opaques and see if they still crack

[beadsoncypress]

be sure to make some cabs from the split beads so they are not a total loss!

[tt4st]

I didn't have any luck encasing kryptonite either. All my beads cracked both times I tried it. They cracked along the mandrel, as if it was a thermal problem, but they were super hot going in. I used 2 different transparents (not clear) to encase. I gave up and just try to remember not to encase it.

[Lorraine Chandler]

You have been making beads long enough it isn't your technique.

Try using the very palest aqua transparent as the casing and see what happens.


Lorraine

[ejralph]

I tried a different brand of bead release once which resulted in loads of cracked beads. Cracks all along the mandrel as though they were thermal. So I know bead release issues can cause these problems.

I ditched that bead release and went back to my regular one and all was ok. Same glass, same beads and no cracks. It could simply have been that I was using the other stuff too thick and needed to water it down a bit - I never actually tried that with the second bead release, although that might have been another solution.

I also just cannot be bothered with CIM for this reason. I have very very few cracked beads overall, and if I do it is usually because I did something dumb. But with CIM glass it was happening a lot. I mean, they had pretty colours and all, but I didn't have the patience to learn how to work with that stuff and sold it all off.

I bet your bead release changing is behind all this, if it isn't a dodgy batch of Cim. Even if the brand of release is the same, it could be a different consistency or itself be a different batch with slightly different proportions of all the ingredients in the mix.

Emma

[Rachel_D]

Hi everyone and thank for all your suggestions. Its reassuring to hear that your Kryptonite beads cracked too Suzanne (I'm sad they cracked but you know what I mean - lol x)

That's interesting about the bead release Emma - I wouldn't ever have considered that would cause problems. It's the same brand I've been using - the stuff last week was right down to bottom so I watered it down a bit. But then I got a new bottle, same brand but the beads still cracked.

This may be a totally daft question but could the age of your mandrels affect the beads? Just wondering whether if they're a couple of years old and have obviously been through the kiln many times whether their heat conduction would be affected?

scaredycat - no I don't think that could have happened as the kiln is made in the Uk and only has the centigrade option.

I've just heated the kiln up to 200 oc and held it there for a while. I placed my sculpey oven thermometer in and at the end it was reading 230 oc. Not sure how accurate this thermometer would be but if the kiln is out by 30 degrees at that temperature it could be way out at hotter.

I know if it was running too low then thermal shock could be a problem but would it still be if it was running too high? I guess that it wouldn't be holding the beads at the correct strain temperature.

[killerbeedz1]

I'd be suspicious of the vetro clear. I have some 1/8 and 3/32 mandrels that are 8 years old. I use the 3/32 all of the time.

[kerryf6]

Yep have a batch of vetro clear, super clear, I think .... cracks every time it is over anything, anything at all, I have to use it by itself with surface decos or surface frits and then it is lovely !!! but over anything else it does crack....

[ChaseDesigns]

You can do a stringer test to test your clear with an opaque to see if it bows. I'd try doing some solid color beads and see if they crack, too. If not it's a compatibility issue. If yes, you know it's an equipment issue.