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  #1  
Old 11-28-2008, 04:08 PM
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Scott Novota Scott Novota is offline
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calcedonio glass

I know I saw someone post some pictures of what looked like calcedonio glass but I can't remember who or what it was titled.

Anyway, I had a guy in my shop with it in his hands and wanted a whole group of glasses made in the same sort of way. Check book in hand.

I know that it is a silver glass and I am guessing some black tin mixed in with it. I kind of blew him off because I did not want to get into it at the time plus I had no idea if I could do with cullet instead of batch.

Anyway....anyone have any ideas as how it could go about playing with getting there with cullet. Black tin and a metric arse load of silver nitrate perhaps?


Scott.
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ED note: I just moved this from the archives ( June '21 )to try to show what used to be an exchange on ideas here. It's scattered all over in there for those willing to take the time to look. I was very specific in what I was doing and any of the people actually melting it had a great time. There were some who just wanted color rods of it. I think it was Greg Vrietoff who said students just want answers, they don't want to think about it. I find that to be quite true much of the time, but here's the calcedonia melted in a fairly high potash glass. I never tried the titanium.
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Old 11-28-2008, 05:20 PM
Eben Horton Eben Horton is offline
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silver nitrate, black tin and red iron, then cook under reduciton Id be more precise, but all of my notes from pete's color class were destroyed when my studio's roof leaked
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Old 11-28-2008, 10:19 PM
Larry Cazes Larry Cazes is offline
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Anybody got a picture of some?
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Old 11-28-2008, 11:51 PM
Mark Halva
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http://shop.aliceglassmurano.com/images/gr-g_.jpg

I believe this is an example.
Mark
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  #5  
Old 11-29-2008, 10:50 AM
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Calcedonia is a color I have been working on for the last month at Josh's. Dino Rosin once told me mine was the best he had ever seen, next to his of course. I am doing one which has a peach blush. I have made calcedonia's in cullet in the past but it is difficult in a cullet that is oxidizing in nature. In about eight pounds of actual glass, I would recommend adding 4.6 grams of silver nitrate, 28 grams of zinc oxide and 28 grams of black tin. Then add two grams of red iron which is key to success in this glass. The iron allows for nucleation points in the glass ( places where crystals or colloids like to form). Melt the glass kind of cold- about 2180F. Melt in a neutral environment. When you gather it, allow the gather to really cool down and then reheat it hard in the gloryhole. If it is going to strike, that will make it happen. Repeated heats intensify the color.

Too much tin makes this stuff brown out . Same to be said about too much silver. It's a touchy feely glass and is notoriously unreliable which is a lot why industry doesn't try to use the color. I do make color rod of it in a 96 but it is a happier glass in a pot. It also performs better if you slap on the gather instead of rotating in the pot which reduces its effectiveness.

Eben, that is too bad about the notes. Can I help with any of that?
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Old 11-29-2008, 11:49 AM
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Ted Trower Ted Trower is offline
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Pete -

Was this your silver opal rod?
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  #7  
Old 11-29-2008, 11:56 AM
Mark Halva
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Pete,
Do you have any color bars for sale?
Mark
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Old 11-29-2008, 12:40 PM
Eben Horton Eben Horton is offline
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Quote:
Originally Posted by Pete VanderLaan View Post


Eben, that is too bad about the notes. Can I help with any of that?
it was really bad. I lost all of my sketchbooks from RIT, Penland, etc.. your class.. basicly all of my 'notes to self' from my entire glass education.
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Old 11-29-2008, 12:49 PM
Edward Dluzen Edward Dluzen is offline
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Does it need to be reducing or can it be done electric?

ed
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Old 11-30-2008, 12:07 AM
Larry Cazes Larry Cazes is offline
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Quote:
Originally Posted by Mark Halva View Post
http://shop.aliceglassmurano.com/images/gr-g_.jpg

I believe this is an example.
Mark
Thanks, Mark. Nice color Pete, if you produce any rod of this please put me on the list for a couple of kilos.
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  #11  
Old 11-30-2008, 08:41 AM
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As I said, it is best in a neutral atmosphere. You supply what reduction you need with black tin ( which I still have some for sale BTW). I did melt it very successfully in my Moly unit in New Mexico. The cold melt allows for large molecules which in turn reflect light while a hot melt makes for smaller molecules that tend to allow for transmissivity.

The color rod I make of this is going to be for sale when I finally get the hot shop running. It is not the peach blush stuff I am making for josh but it will be like my original stuff. As I said, it is still best from the pot, not as a rod. That is true of cad sel reds as well. We are moving forward on the shop. The horses are finally in their barn and I am cleaning out the studio space since my new three pot furnace is on its way from Steve's on a fed ex freight truck. It will take a while to make new benches, pipe coolers, and to rebuild one of the lehrs but I could be going by Christmas. I am running out of money at this point. Two years of construction is taking a toll.
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Old 12-02-2008, 09:43 PM
Edward Dluzen Edward Dluzen is offline
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Sorry Pete, I missed the Neutral part in your message. Glad things are going reasonably well.

ed
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Old 12-03-2008, 07:09 PM
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Pete,

Would this be the same if mixed in batch, and how long is the cook time at that temp? Or did I miss that in the post?

Thanks
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Old 12-03-2008, 07:25 PM
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I gave a very rough calc for cullet gary. The silver content is pretty fine and you have to keep in mind the carbon dioxide loss in a batch at around 17 percent as opposed to cullet which is zero. I will give you what I have been doing in a batch for josh.

10 lbs batch
4.6 grams silver nitrate
28 grams zinc oxide
28 grams black tin oxide
2 grams red iron
melt cold 2150-2175

The time to melt and fine ( I hate the term "Cook") really varies from furnace to furnace. It's slow to fine without borax.

Take note that the silver is in tenths of a gram and deviation on that makes a big difference. It's a powerful colorant. You can also note that the stuff I posted for last week had the same additives but used 8 lbs of cullet. Thats the rough part of the C02 loss.

I did melt this in SP a number of years back and firstly, you had to use the colorbase, not the regular oxidized batch or you didn't show color at all. When I did use it, it muddied up somewhat brown and I didn't pursue it. I did suspect the feldspar at the time which was a kona F4 if I recall correctly. The batch I worked for Josh was ( ahem) cheap. It was a soda glass with some borax in it to reduce viscosity. We used regular whiting, and did use that kona spar again. I needed to use materials that Tom keeps in stock at Spruce Pine since he did the mixing as tonnage once I provided the formulation.

And remember that the colorbase from tom needs to be mixed when you get it. It's not premixed like SP87 is.

I hope that helps.
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Old 12-07-2008, 10:46 AM
Dave Bross Dave Bross is offline
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Wow! I melted this in some pots in the glory yesterday and this glass is just terriffic fun. It does radically different things depending on how you heat and cool it for striking, all of it good looking unless you strike it too far, and even that's pretty as tan/brown goes. The crazy multi color stripes are my favorite.

I'm going to try Jon Myer's trick of nucleating it with titanium and see what that brings.

It does work a ton better hot from the pot. We were playing with some of the old flying colors rods of this at Barb's last summer and really had to work to get the strike.

Thanks for putting that out there Pete. I love it when you have enough info to hit something on the first melt.
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Old 12-07-2008, 11:07 AM
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I am always glad to run into people who actually are following in the path. I certainly learned at the feet of Dudley Gibberson, Mark Peiser and Chuck Savoie. It seems to me that glass workers suffer from a periodic loss of all useful information about every eighty years, mostly because people believed they had to be secretive. It gives me a lot of pleasure to see people actually trying some of this stuff instead of continuing to believe that it can't be done or is way too costly to do ( it's actually much cheaper than color rods) or just too scary to do.

try adding four or five grams of red copper.
Salt does interesting things too.

If it is browning out, back off on the silver by a few tenths of a gram.
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Old 12-08-2008, 11:12 AM
Dave Bross Dave Bross is offline
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Yeah, the regularly scheduled loss of information on glass tech makes me nuts too.

The melt with titanium instead of iron did just what Jon said, nothing browner than a carmel color and muchly delayed striking. See this thread for details: http://talk.craftweb.com/showthread.php?t=6570

The colors weren't as wild and crazy as the iron melt and the delay in striking was such that I had to strike it repeatedly (heat/cool) to get it to where I wanted it. I prefer the iron version from the standpoint of faster production, more different colors and the dificulty of measuring the tiny amount of titanium required, but if you needed tight control on the strike for a specific effect, and were not in a hurry, the titanium would be good.

I've long been thinking about how to delay/control striking on other glasses such as copper ruby and cad/sel red. The thought crossed my mind that the titanium may be worth trying in case it would delay or decrease the strike on those two.

I'll salt and copper the next version along with the iron and see what happens. I put 5 grams salt in 10# of batch on the titanium melt and I now see why it has been used for a long time as a fining agent for reduction/neutral glasses. One of my goals is lowest possible toxicity in glass batching and halogens don't do so well there. Not overly helpful for element life either. I only tried the salt because I was melting in the glory.
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Old 12-08-2008, 07:33 PM
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Dave what is the size of your glory again?
Franklin
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Old 12-09-2008, 10:58 AM
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It's about a cubic foot inside, it's square. I can get three #5 assay pots in the back (that will melt 10# of batch)and still have enough room to work a gather of the size I need for what I do (small). It has a hatch on the top rear to get at the pots to gather. You need a face`shield and gloves to gather from it or it will smoke your face and hands. Reminds me of Dudley's comment about one of his old furnaces: "you need asbestos underwear to gather from it". It also sits way higher than most, hole at eye level for me (I'm 6' tall), so there's a set of old mobile home steps by the hatch so I can climb up high enough to see what I'm doing (as opposed to knowing what I'm doing) and I can free my hands to dance to the music while reheating with the pipe resting on my shoulder and the yoke. More trailer trash glass doings.
I've even put a cheap-o K thermocouple through the back wall and hooked it to a brain dead controller that still reads temp OK so I have some idea of temps. I'll melt oxidised cullets in there and I want to know the temp so I don't go past the valence switch on the antimony (about 2170F) and reboil the glass. This also helped me figure out how to make those Spectrum transparent cullets with sulphur in them (red, yellow, orange) strike opaque. Melt them under 2000 F in anything from slightly to extremely reducing atmosphere. I can fine an oxidised cullet in around 2 hours but that goes out to 4-5 hours if I reboil it. It runs a homemade pipe burner like the rednecks here use on their fish cookers. 3/4 pipe with a #70 orfice burning propane.

How's that for too much information?

And an update on the titanium nucleated glass. When I got the stuff out of the annealer both the brown base color and the psychedelia on the surface had struck further and I can't tell it from the iron nucleated glass. It must strike more in the annealer because the ones I fumbled and left out to pop were very different, as in much lighter brown and not as much other whirly/swirly color.
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Old 12-09-2008, 11:41 AM
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Thanks Dave, I now realise how you save your elements from burning out. I did not realise how corosive the gases from batching was until I tried it a few times and it ate my elements to the bone.
I need to stock up on wire to go at that again.
Franklin
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Old 12-10-2008, 05:43 AM
Dave Bross Dave Bross is offline
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I still use batch in my wire melters. I'm forever spoiled by being able to dial in all my working characteristics, prettier glass, and locally available materials. Any cullet I've ever found that I like usually disappears shortly after I discover it anyway. Cullet does make wire melter elements go WAY longer but I've discovered a few things to make the elements live longer with batch, like having small vent holes below the elements and cracking the lid while melting so there's a chimney effect updraft through the furnace and almost, not quite sealing the rim of the pot to the opening so very little can go down by the elements. Hopefully that updraft keeps all the fumes heading up and out.

The glory melt is just a great way to have multiple hot colors or color and clear without running furnace #2. It's sitting there burning propane anyway, it might as well do something else useful.

I would love to see propane prices drop. From the reliability, ease of furnace building, and dial-an-atmosphere benefits you get with gas melting I do believe I wouldn't mind melting everything with gas if the fuel prices were more reasonable. It's getting old having to swap elements and losing pots when you least expected or wanted to.
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Old 12-12-2008, 09:03 AM
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I forgot the holes. I put them in mine after you mentioned them. I wonder if that is why I seem to loose more heat than the last furnace I had. ie Loose more heat or use more heat . It is not very much but somehow you feel cheated by the electricity company if you dont squeeze them out of the last penny.
Franklin
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Old 12-12-2008, 07:13 PM
Dan Ellis Dan Ellis is offline
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Just curious, When you set a pot in your gloryhole how long does it take for the glass to become usable?
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Old 12-12-2008, 08:34 PM
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I think the way Ed Skeels was doing it was to have the pot in the gloryhole and to keep color rod sections in the annealer. He would move them from point A to point B and since they were hot, they didn't shatter and were ready in just a few minutes. You would need to use them right away if they are leaded rods or the lead separates out very quickly and it all looks awful. Nice for lip wraps though.
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Old 12-12-2008, 08:50 PM
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Cullet of oxidised glass (most clear and colors) about 2-4 hours if you keep it below the point where it will reboil, roughly 2170F.
4-6 hours if you just let it rip temperature wise and let it reboil and then fine out from there.
Lower viscosity or higher temps = quicker fining

I've only done batch of neutral or reducing glass (no oxidisers, so no fining action from the nitrate/antimony combo) or phosphates where seed bubbles can't be seen and so they're not an issue. I can bring the reducing or neutral glasses in to what we'll call "useable" at about 8-10 hours if I add things that really drop the viscosity. There will still be some seeds at the 8-10 hour point. The added viscosity droppers bring up issues of one glass fitting another for you to deal with too. You would probably have to go overnight to get a clean transparent in these. The phosphates, where we're not worried about seed bubs, are good to go as soon as they're melted, so 2-4 hours.
Oxidising batch would be dificult because you would have to turn down the temp to fine it and it wouldn't be easy to reheat work at the same time in that cool a glory.
The silver glasses we're discussing in this thread go mostly opaque in the swirls so the little bubs aren't noticeable. I batch 'em up early and let them go until the end of the day.
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