calcedonio glass

[Pete VanderLaan]

Originally Posted by Eben Horton

what COE is double helix's glass? Furthermore, what kind of operation would sell glass to glass makers and not tell you anything about compatability or how they test it??

Their colors are beautiful however..

^^^^^^^^^^^^
Dan is correct. It is for lampworkers only.

[Dave Bross]

Yeah Pete, I'm beginning to understand why that nice triple beam balance I bought way back is about to become a favored tool. Amazing power in some of these colorants given the right conditions.

[Pete VanderLaan]

It also says a lot about having good atmospheric controls on the furnace, both air and gas. I use a lot of Dwyer flowmeters for both. In the electric furnace, attention to the surface area of the crucible gets to being important in as you will need to adjust your localized ( in glass) R/O conditions in the glass. I still cannot make a great copper ruby in an electric box. It's OK but not great.

[Eben Horton]

Originally Posted by Pete VanderLaan

It also says a lot about having good atmospheric controls on the furnace, both air and gas. I use a lot of Dwyer flowmeters for both. In the electric furnace, attention to the surface area of the crucible gets to being important in as you will need to adjust your localized ( in glass) R/O conditions in the glass. I still cannot make a great copper ruby in an electric box. It's OK but not great.

Eben reccomends an automatic peanut M&M dropper for your furnace-

[Dave Bross]

Mmmmmmmmmmmmmmm high carbon content food/fuel pellets. Would it feed the operator too?

Pavlov's glassworker...bad glass = no treat.

When you guys talk about adding salt, is that just regular table salt? sea salt to keep the cholesterol down? I've never heard of adding it to batch, but im still kinda new i guess.

Also i was wondering how much actual batch to load at a time. melting in a 40lber i think. the crucible is about 10-12" in dia. i tried melting it once and got stones real bad i suspect because i loaded too much at a time. I usually charge a regular silver glass in that pot by 4-5lb/hr but i also stir between loads and potato at the end. for this glass i did even less maybe 1-1.5lb scoops in a nice even layer. it looked like it was melting out ok. i did not stir/rake at all and no potato. is it ok to rake this glass while it is melting? maybe 30-40minutes after a charge. i thought i shouldnt since its better not to rotate when gathering, so better not to rotate while melting?

[Pete VanderLaan]

quantity loaded is directly related to furnace temperature and the capacity of the furnace to rebound Scott. My 40lb pot is 11 inches across and eight inches deep ( which I do sell by the way...) I usually charge it at about 2250F with a batch similar to SP87, First charge is about 20 lbs and takes about an hour and fifteen minutes to go totally flat. Second charge is smaller, about 14 lbs, until the brim is reached with a similar rebound time.. As time goes by, the charges get smaller and smaller. The last inch is a PIA. Important to remember is allowing the charge to go completely flat. If you put more batch in on top of a mound not thoroughly melted, you will get batch stones for sure.

It indeed is ordinary table salt- sodium chloride being referred to. It is a curious additive to glass that I seldom use. Chlorine does not occur in glass and is driven out in the melt. It does seem to affect opalescence in colloidal glass structures.

I don't think raking a glass either helps or hurts in a silver glass. In some glasses- cad sels in particular it can have bad results. In general, it should melt fine without worrying it to death or there was some other fundamental problem. I don't understand the rotation reference.

Originally Posted by Pete VanderLaan

quantity loaded is directly related to furnace temperature and the capacity of the furnace to rebound Scott. My 40lb pot is 11 inches across and eight inches deep ( which I do sell by the way...) I usually charge it at about 2250F with a batch similar to SP87, First charge is about 20 lbs and takes about an hour and fifteen minutes to go totally flat. Second charge is smaller, about 14 lbs, until the brim is reached with a similar rebound time.. As time goes by, the charges get smaller and smaller. The last inch is a PIA. Important to remember is allowing the charge to go completely flat. If you put more batch in on top of a mound not thoroughly melted, you will get batch stones for sure.

i also melt regular silver at 2250.. the thing is, this isnt a normal silver and we arent melting it at 2250. what size pot have/are you melting chalcedonia and what kind of charge schedule do you follow in that pot?

[Pete VanderLaan]

To me it is a conventional silver glass with no fining agents that is induced to reduce silver and copper through stannous oxide with zinc oxide as a mild opacifier. Iron is used to create a nucleation point for the colloidal structures to come into existence. Jon has suggested titanium for that as well. I think a glass high in potash would be best. The cleanest source of calcium is a really good idea, as in hydrated food grade lime. I hate whiting. It is so dirty. I melt it in 40 lb pots for the most part at 2175 preferably and turn it up after the melt is done to 2275F. Josh has simply been beating on it at 2300F and it seems to work fine. I just dump the stuff in the pot until it's full.

Most of the time it works, sometimes it don't. which is why industry hates the stuff. The least little bit of an oxidizer will do it in. I suspect but have never tried, making it with a chloride instead of a nitrate for what I think should be obvious reasons.

[Dave Bross]

As for chlorides...salt (sodium chloride)will definitely make for more psychedelia and faster fining. I was using very pure canning salt but I think I'll try some sea salt next time. There's many different minerals in sea salt and it may increase the effect.

[Pete VanderLaan]

I meant silver chloride, not silver nitrate.

[Dave Bross]

Ohhhh, OK, less oxygen. Got it!

[Pete VanderLaan]

well, I'm just curious. My old fire department brain says Chlorine is indeed an oxidizer but I'm not clear as to how that works. I do think removing any oxygen from the melt is a good idea.

[Dave Bross]

Aren't the halogens super reactive with almost anything because of being so electro negative? Would that get them listed in with the oxidisers on the basis of the extreme reactivity for purposes of firefighting?

[Pete VanderLaan]

I simply don't know.

[Dave Bross]

Here we go:

"Chlorine is an oxidizer. It reacts with many organic materials. Chlorine may react explosively with many metal powders or metal filings, for example, aluminum. A person might ask, “how can chlorine be an oxidizer if it contains no oxygen?” The answer is that chlorine easily pulls electrons off of many other chemicals in much the same way that oxygen does during burning. A lot of heat energy is released during the process. Sometimes the energy is released explosively."


That's from:

http://www.aristatek.com/Newsletter/...20Speaking.htm

Back in the high school days, a friend lost an ear trying to build a gasoline/chlorine rocket from an old motorcycle muffler. He didn't realize just how violent that reaction would be. He was lucky that he only got "premature launch" with ear removal instead of detonation and shrapnel.

[Pete VanderLaan]

well then, using chloride isn't going to change things much. The bromide form is hard as a rock and once again, I don't know what would occur with the iodide form. I suppose fine silver dust would be best but I would wager that it's explosive not to mention hard to get reasonably.