All of my black blow-ins check and the cobalt ones are fine???

[Jerry Gash]

So i made a bunch of spoons yesterday all made with blow-ins using some black tubing i picked up from ABR, what a disappointment, every single piece i made with the black tubing checked. IT was weird a few of them were fine, i set them down on my bench and i heard a "tink" sure enough the ones that i thought were gonna be ok just started cracking.....oh well at least i had fun making them.

[The Glass Fish]

How much did you work the tube after the blow-in? It is possible that the color and clear never really got a deep weld. After you sleeve or blow in you really need to change the shape of the tube. Blow and shrink, push and pull. Really work the tube to get it together all the way through. If you just do a blow-in and make a very basic tube shaped spoon, the inside and outside aren't really one piece yet. Try manipulating the tubing to really get the matrix stable.

If that doesn't work.....well i've heard a lot of people had problems with the imported black. Don't give up though, keep trying.

[Firekist]

um... set them down on your bench? if you're trying to bench cool the black.. that's ballsy.. hard to do.

if you mean you took them out of the kiln, after being properly annealed, and then they checked... that's pretty weird.

black tube can be a pain. get it rippin hot when you make the piece, cause it doesn't melt as easily as other colors. too thick can lead to problems. too much kiln time seems to have been an issue for me on a couple pieces..

i would'nt be surprised if there are some pretty shoddy tubes of it now and then.

bummed about the checking.. that always makes me feel like i just ate bad sushi.

z---seth how far are you from rochester/ or the road from roch to iowa city?

[LoneWolfandSon]

hey jerry,

i have been listening to glasscaster by marcie davis (podcast check it out). well she had a interview with henry halem that wrote glass notes. he went into great depth about how if you work cads to long or to hard that you can change the composition of the glass. you can change it so much that it wont even be compatiable with it self. so basically you can work say yellow to long add more of the same yellow that they wont be compatiable anymore. i dont know if black is a cadium i think it is this might be the problem. he did say basically when you work these colors to work fast and keep it soft on the colors. heres a link to the glasscaster site. check out all the interviews very informative.

http://www.fireladyproductions.com/Site/Podcasts/Podcasts.html

[Mecha]

I think black tubing is made with cobalt. Just a lot of it. The black tubing is dodgy anyway. It is really shocky when you work it. You have to be super careful introducing to the flame and it seems even more prone to exploding after it has been worked, annealed and then re introduced to the flame. It also seems to vary quite a bit from piece to piece as far as shocky-ness is concerned. Maybe it just can't be encased, or maybe you just got a bad tube(s)? It is from China and the quality control standards are not really the greatest.

[Jerry Gash]

Thanks for the help, i guess it could be a couple of things, i just got the delta elite so i am probably overworking it because i was afraid that if i didnt the black wouldnt totally be locked into the clean. Another reason could be i have been garaging the pieces at 1050 for long periods of time, like overnight and stuff, i think i'll try a couple tests tonight and see if ic an get the problem narrowed down.

Firekist: I am in Waterloo, which is right on the way to IC, feel free to stop by sometime if your in the area.

Thanks for all the help guys.

J

[Dom]

Black tubing is made with green so garaging too long could be a problem.

Another thing, how much black are you using to blow in? If you use too much color I could see that it would check, the black especially is really saturated and opaque, so a little bit goes a long way.

[The Glass Fish]

One more thing I wanted to add, but not about the black: anytime you use a new tech or a new color, only do a couple of cheap pieces the first day. Nothing worse than trying a new color untested and losing a whole day, or an untried color on a heady. Patience is the key. Try out the tech, then forget until you pull the piece out of the kiln the next day.

This could be an expensive lesson if repeated too often. I spent all day once trying a new color and I didn't use it right. I lost like six hours of labor because I didn't test properly. The great thing about this forum is you can learn from others mistakes as well as your own.

[Mecha]

^^ That's for sure. Think loch ness and unobtainium deeply encased. :bangHead:

[nicko0]

i use chinese black for blowins work the hell out of them and garage for up to 40 hours at 1050. im guessing chinese black is made with manganese as well as chrome like ga raven because its so saturated. i guess im lucky to get away with overworking overkilning. my rampdown is very slow it takes 3 hours to reach 950.

[Firekist]

ditto on the using chinese black for blowins.. i've never had checking as a problem, even when kilned at 1100 all day. sleeving i've had a couple problems.

really, i have no good reason for your checking. doesn't make much sense to me.

z---seth sorry =-( heh

[VinE]

i use chinese black for blowins work the hell out of them and garage for up to 40 hours at 1050. im guessing chinese black is made with manganese as well as chrome like ga raven because its so saturated. i guess im lucky to get away with overworking overkilning. my rampdown is very slow it takes 3 hours to reach 950.

You really kiln your stuff for 40 hours?

[Arik]

I have alot of probs with blow-ins, I tube suck medium over the china black, never causes any probs, no garaging needed. I also try not to thin out the china black, and then push it back thick again....that is what causes stress issues in my experience. I get away with "shrinking the diameter" into thickening, but "pushing" it thicker sometimes causes subteranian checking.