Chalcedony, Silver Opal

[Ed Pennebaker]

I melted a new color this week. It looks pretty good but I would like a little more red tone to it. It is a dark amber in transmitted light. Recipe for 100 pounds Spruce Pine Color Base
300 gm zinc oxide
280 gm black tin
46 gm silver nitrate
20 gm red iron oxide
melted at 2125, taken up to 2260 7 hours after last charge.
Fairly seedy first day, fewer very small seeds second day.

Should I use a little less red iron or less silver nitrate?

[Chris Lowry]

I really know nothing but the old guys talked about adding sugar to help reduction.

[Pete VanderLaan]

Chalcedonias really like potash and really don't like sodium. zinc and black tin are OK silver seems high, iron somwhat low, melt a lot hotter. Neutral flame. Don't add sugar. That glass will be a slight mismatch for SP87

Read the first sentence again.

[Ed Pennebaker]

"Chalcedonias really like potash and really don't like sodium". So I assume that means I would need some potash to help it go toward the red instead of browning out.

[Pete VanderLaan]

several things can cause the browning. The first I would indeed say is the sodium content which you can't reduce since it's pre mixed. Second would be the excess silver and it's very touchy as to when is too little and too much. In my own formulations, two grams either way makes for a major shift. The batch doesn't need more zinc since the base has lots. Iron can be strange, Too little and it just strikes poorly, Too much and the same thing happens but the non strike is very different.

Also heating and cooling those glasses is really important for the strike. If it is turning amber prior to any reheat, it has probably got too much silver. I can't quite put a finger on it because of the sodium which I avoid so I don't really get to see its influence.
Reds come from adding a remarkably small amount of copper. They strike in the annealer.

[Greg Vriethoff]

Neato!

(Seriously. I love this stuff.)

[Larry Cazes]

Originally Posted by Ed Pennebaker

I melted a new color this week. It looks pretty good but I would like a little more red tone to it. It is a dark amber in transmitted light. Recipe for 100 pounds Spruce Pine Color Base
300 gm zinc oxide
280 gm black tin
46 gm silver nitrate
20 gm red iron oxide
melted at 2125, taken up to 2260 7 hours after last charge.
Fairly seedy first day, fewer very small seeds second day.

Should I use a little less red iron or less silver nitrate?

Thats really nice!

[Ed Pennebaker]

The second batch does have better color I think, the photo make it look a little more red than it actually is. But it has some deep maroon, purple and blue. Decreased silver by 2 grams, added 60 gm black copper, melted hotter. It does strike some color in the annealer. The best color pieces are put in early in the day at the back of the annealer. I had to make a batch of cobalt between the two batches of Chalcedony so there was some extra cobalt also. Early checks on melt progress without reheating the glass looked like a light cobalt I usually make with 3 grams of cobalt in 100 lb of SP87 plain batch. It is still very dark amber in transmitted light.

[Pete VanderLaan]

That looks great Ed! I think you can back off of the copper even more. Those glasses don't take kindly to being gathered. It tends to mix the colors up. Slapping it on the side of a piece is more effective, or taking rope like gathers that are slapped and then drawing them out and annealing them to be picked up later on the sides.

When I wrote the formulas for the Corona glass Josh Simpson was making, I told him he could only do three, perhaps four pieces a day unless he was willing to set up a second pot for the color. The surface of the pot is affected by local reduction but as you get into the melt, that slows way down and the stuff tends to turn either gray or eggnog color. You can draw it up if you chuck tiny balls of wax into the pot and gather quickly. Simpson used a rather large oxy acetylene torch on the pot surface. It all works.

[Ed Pennebaker]

Since I only have one furnace, one pot I take a gather or two, pinch, cut, and mess with it getting the gather very uneven until rather cool. Then reheat to develop the color. I have to reheat and block it several times to get it even again. Timing is difficult to get down, no two pieces the same but I like what it is doing.

[Pete VanderLaan]

well, it looks nice. I'm glad to see the reduction in the quantity of silver worked out. Do stay away from the sugar and it already has lots of Zinc from the SP87.

[Eben Horton]

Beautiful stuff Ed !!

[Scott Dunahee]

just for giggles, before you pinch and abuse up the gather, roll it in some other silver bearing color frit. Trust me. Or at least try it....

BSD

p.s. those look great, Ed.

[Pete VanderLaan]

tiny copper wires... think tiny copper wires, really small.

[Bradley Howes]

Originally Posted by Pete VanderLaan

.When I wrote the formulas for the Corona glass Josh Simpson was making, I told him he could only do three, perhaps four pieces a day unless he was willing to set up a second pot for the color. The surface of the pot is affected by local reduction but as you get into the melt, that slows way down and the stuff tends to turn either gray or eggnog color. You can draw it up if you chuck tiny balls of wax into the pot and gather quickly. Simpson used a rather large oxy acetylene torch on the pot surface. It all works.

Are you able to share any info on the flame settings or anything for the torch trick? I just found a premix torch with a really long neck that might work. I’d be running it on oxy propane though. I’d never given it much thought until now due to the lack of an appropriate torch.

[Pete VanderLaan]

It was all seat of the pants with lots of gas. The goal was trying to keep the upper 1/2 inch active. In any of these glasses, the DNA is right there in the glass but the thermal treatment is what kicks it. That includes the time at the gloryhole, blah blah blah. Glass composition is really important. I can't keep stressing that enough.

[Art Freas]

Originally Posted by Pete VanderLaan

tiny copper wires... think tiny copper wires, really small.

https://www.amazon.com/Redecker-Non-...dDbGljaz10cnVl

[David Hopman]

https://www.amazon.com/s?k=copper+ro...b_sb_ss_i_1_13

[Pete VanderLaan]

Don't get crazy, any good hardware store will have copper window screen. Don't use too much .

[Ed Pennebaker]

I have used all my Spruce Pine Color Base so am getting ready to make my own batch for this next batch of chalcedony. Was thinking of using Pete's Neutral Base clear as the starting point but noticed it has no zinc. Any other suggestions for the base glass?

[Pete VanderLaan]

That base works fine, you just need to add the zinc as an additive. Use about the same amount as you would of the black tin. It's going to need some flux to keep it compatible with your host clear. Around 50 grams in 80 lbs.

Little wax balls thrown in the pot just prior to gathering will light the stuff up.

I'm copying this thread to the color board where I think it really belongs.

[Ed Pennebaker]

Thanks, that sounds easy. Will mix it up this afternoon, melt Sunday.

[Pete VanderLaan]

SP base has a tendency in my experience to push silver opals in the brown direction which I think is the spar but the spar has changed over the years with the loss on KONA. Minispar is a lot nicer. I haven't used SP's color base since the second color class really. Mine works well although it's a bit alumina deficient.

[Josh Bernbaum]

Originally Posted by Pete VanderLaan

Little wax balls thrown in the pot just prior to gathering will light the stuff up.

I'd like to hear a bit more on this please.

[Pete VanderLaan]

Make tiny wax balls 1/2 to 3/4 inch . Throw one on the top of the pot of silver glass. It will cause a very short term intense reduction of the surface glass, but just the surface. .

Gather the glass, or preferably, slap it on the side of your piece. Gathering requires turning it and that mixes it and that stuff tends to turn gray which is decidedly not very pretty. It's why I told Simpson that the corona series would be limited to a few pieces per day unless he set up multiple pots. I never broached the subject of the wax with him.

It also doesn't always work. Sometimes, not at all. The base glass in the pot needs to be receptive to a sudden rush on the outer electron ring. Potassium is such nice stuff.