Cold boro in hot kiln?

Floorkasp · #1 2014-02-20, 4:35am

A boro newbie here. I am trying to sort out how to get started using boro at my home studio. I have done soft glass for about 6 months, and took a boro class a few weeks ago.

With the soft glass, I have batch annealed pretty much everything, so I am now trying to figure out what would work best for the boro glass. It will be mostly smaller beads, marbles and pendants. My kiln is a bead cube, with a digital controller.

My questions:
- At the class, I would put glass pieces that had gone cold into the kiln at garaging temperature (950 F). I would never do this with soft glass, but is it okay to do with boro? For example: I made a glass chain in the class about a yard long. I made it in one go, so by the time I was making the 4th link, the first link would be cold. So when it went into the kiln, 95% of the chain was room temperature.
- Can I batch anneal boro pieces?
- If I have non striking colors (like crayon colors) can I put those through a striking program together with the striking colors, or would that be a bad idea?

Thanks!

laserglass · #2 2014-02-20, 5:35am

the thermal expansion of boro is about 30% that of soft glass, so it is more thermal shock tolerant, but you can get into problems with large boro pieces doing what you described....and the annealing temperature for boro is 1050 not 950, so the annealing is not happening at 950....

Bunyip · #3 2014-02-20, 5:44am

Yes you can batch anneal boro. For maximum safety never put cold pieces into a hot kiln. However, as noted above Borosilicate glass is far more thermally stable than soft glass. It all comes down to your risk tolerance.

I wouldn't hesitate to put a room temperature 3mm boro rod into a hot kiln, but a 2" marble? Probably not a good idea. Personally, I have not had issues with putting the pendants I make into a hot kiln even after they have cooled.

Floorkasp · #4 2014-02-20, 5:55am

Thanks Chris and Mark. Guess I'll have to figure out my risk tolerance.
Mark, just so I have understood correctly: 950 is the garaging temperature, after which I would ramp up to 1050 for annealing, right? And if I want it to strike, after garaging I first go up to 1225, then to 1050?
Guess part of it is just testing, and seeing what works.

istandalone24/7 · #5 2014-02-22, 8:07am

this is where contemporary lampworking vols 1 & 2 come in handy