Effetre Navy blue cracks when encased

Irene · March 10, 2014, 10:36:11 PM

This is so frustrating! I bought the beautiful navy blue from effetre, but when I encase it With Clear they crack. Almost every one! It happens after they come out of the kiln, even after a day or so, I think they will be fine, and then the NeXT day they have cracked just lying there on the table. Looks like it is mostly the Clear that is cracking. I use effetre Clear and also New Clear. Same thing. I tried two different ramp Downs in my kiln too, one really really slow With hold time and everything taking many hours to ramp Down to about 75 degrees C. Never take them out until room temperatur. What can I do to fix this? I so love the color when encased.

Jellybean · March 10, 2014, 10:42:42 PM

Oh no

Can't say I've had that problem. Just ran to the bead box to check the one I have, and it's fine. Made weeks ago. Not sure which clear I used but it would have been 006, but do have a habit of using DH Zephyr. Navy is such a pretty colour encased. Will try one with 006 tomorrow and see if it survives

Trudi · March 10, 2014, 11:06:15 PM

Maybe try encasing with another colour .... baby blue?

Irene · March 11, 2014, 12:20:35 AM

well I could try another colour for encasing but then it wouldn't be the navy colour anymore.... And I have plans for these beads together With some colour combinations I really like, I will not give up. Just cant figure out what to do or not to do, I hardly never have other beads crack at all.

SilverGems89 · March 11, 2014, 05:47:38 AM

It's strange because they look more like thermal cracks than incompatibility, incompatible glass tends to crack in a "crazed" pattern and nice straight cracks along the mandrel line are more commonly associated with thermal shock, I wonder if the navy perhaps wants a higher or long anneal? I would try Trudi's suggestion of trying some different colours and even different clears to encase also to see if you can eliminate the problems that way

Miriam · March 11, 2014, 06:05:09 AM

They are for sure incompatibility cracks. Some colors don't like to be encased. If you make the core the same clear as you use for encasing, the beads are more likely to survive. The blue is then sandwiched between the cleat and can do no harm.

theflyingbedstead · March 11, 2014, 09:07:36 AM

That's odd - i've encased it without problems - I've used lauscha clear.

Irene · March 11, 2014, 02:06:33 PM

the Clear I have used is the "old" 004 and the newer 006. I'm going to try a different glass to encase, just to see if they still crack.... I will try to have a core of Clear and then the blue and encasing over that. The beads are small, I would say about 1 to 1,5 cm in diameter. I garage at 500 degrees while working and then they are annealed for 1 hour at temperature 519 degrees C. Perhaps this is not correct annealing temp? Slowly ramp Down to 450 degrees, and again Down to 250. Then it turns off and is left to room temperature. I have also tried a slower ramp With holding time of 30 min. before ramping Down, in I think 3 steps. End temp is 75 degrees, and left to room temp.

MangoBeads · March 11, 2014, 03:52:14 PM

I have had a similar issue too encasing with 006 and other colours too

just one of those things I think - a shame as it is a beautiful colour ! Great advise from Miriam !

Irene · March 15, 2014, 03:39:10 PM

So thinking, and hoping, that it was thermal cracks (then it would be possible to do something about it..) I put the encased beads in to the kiln sooner, while I could still see a Bright glow in the bead, thinking I had left my previous beads to cool for too long before garaging them. And I think I am on to something. The glow in the blue color tricks me into waiting too long before putting the beads in the kiln, thinking they are still too hot and will be deformed if I put them in, and the result is that the encasing layer is getting too Cold befor they are put in the kiln. Now I put them in earlier and almost all of them are fine, at least for now. I will give them a few more days before Im confident about it.
Here is a Picture of yesterdays beads

Pat from Canvey · March 16, 2014, 07:24:22 AM

If I'm unsure about whether a bead is cool enough to go in the kiln, I put it in anyway and continue to turn the mandrel for a minute or so before finally letting the bead rest on it's support and shutting the kiln bead door. Epecially good for very large focal beads.

Dragonfire Glass · March 16, 2014, 07:44:59 AM

I do that too Pat

JoyWhoKnits · March 16, 2014, 10:05:05 AM

Probably a silly question - but if the clear and navy are incomparable then why does using a clear core reduce that? Is it because there's less navy? ( so the same idea as different frit being ok if you don't use much)

Otherwise using a clear core is going to give two layers which don't behave the same way rather than one.

Jellybean · March 16, 2014, 12:43:26 PM

I thinly encased navy with 006 yesterday (the other bead I did was thickly encased) and it seems fine at the moment

Miriam · March 17, 2014, 07:00:34 AM

"Sandwiching" a color makes it easier to accept any difference in shrinking or expanding. There is more glass to cope with the different glass, like you said with an other COE fritt. Not only the COE is an important factor, viscosity is important too!!

An other advantage of using a clear core is that the clear is stiffer and you can retain your shape better. And using a clear core gives you a chance to use your crappy clear. ;-)