CraftWEB Hot Glass Talk

CraftWEB Hot Glass Talk (
-   Antiques & Classics (
-   -   help with adding color to 4c cullet (

Kevin Bethea 03-04-2006 10:38 AM

help with adding color to 4c cullet
I know it's opening a big can of worms so if anyone can point me in the right direction I am willing to do the research and I would appreciate the help. I am a new student and I am just trying to get something different than black and cobalt blue. I have seen a red attempted but it came out green. I saw a sample that was melted a couple years ago and it was real livery and brown but no surprise there. I have seen a bucket marked green but we only have 2 colors that we melt. Our current method is to mix the colorants and cullet in a 5 gallon bucket then charge into a small 4 pot gas fired furnace. I don't think there is a squeeze or anything like that but I guess we could if we had to. I asked a few advanced students why we only had a few colors and they answered something like if there were other colors the guy that built the furnace would have known about it. I mean I know we can't do any expensive melts but there has to be something else and I would like to get some numbers together so I know how much not to exceed when adding stuff so it will still fit the base and all that. I know it's a big question and it's been covered before so I would be happy with a nudge in the right direction. I am willing to experiment but I know there are more than 2 colors we can melt. It'd be fun trying anyway. They might not be red, yellow, or orange but I'd be happy with puke green and purple. I own Weyl's "colored glasses" but it's a little above my head still. I can feel the eyes rolling now but I won't know where to start my research if I don't ask. sorry for the dumb question.
Kevin Bethea

Pete VanderLaan 03-04-2006 10:56 AM

It's not a dumb question Kevin. I don't have the time right this minute to go into detail but you can get some more colors than you are currently getting. Before you get anything from me though you need to do something first. Go get the clear furnace nice and hot and ladle a lot of the clear into very cold water allowing the glass to enter the water as a fine stream. If the water warms up, get more cold water. You are going to need a fine frit to do the things I will suggest. Make a bunch of it. Bug lumpy chunks of cullet make for hard coloring.

Then call up standard Ceramics in Pittsburg and order manganese dioxide, cuprous oxide ( red copper), nickel oxide,,ferrous oxide and about fifty grams of silver nitrate. The silver won't come from Standard and that will be a good start. Get about ten pounds of each, maybe 20 of the manganese. It at least is cheap. You will need to also get some black tin somewhere but Standard won't have it. Seattle Pottery might. I don't want to sell more of my stock.

Then report back and I will begin to lead you down the yellow brick road. to C-4 happiness.

Kevin Bethea 03-04-2006 11:08 AM

wow. Thanks Pete. I'll report back when I get the stuff together. I need to see what we have already too and I might find the tin or something. I am going up there now to assist someone for a while so I should have time to have him show me what we have. That's awesome. I appreciate it. I knew it was going to be a time consuming question so I was scared to ask it but when they said there weren't any colors I just laughed because I have read enough to know better.
Kevin Bethea

Mitcheal Veenstra 03-04-2006 11:21 AM

(getting pencil and paper ready... a cullet coloring class online!)

Thanks Pete!

Brian Graham 03-04-2006 11:24 AM

Copper blue.....
Gabbert will make a nice turquoise blue when mixed with the copper oxide. We used to mix a very small quantity with about 100 pounds of freshly washed cullet - right in the paper drum. You just roll it around on the ground for awhile to mix - the little bit of moisture from the washing process makes the powder stick to the cullet. Let it sit for a day and then charge as usual. It would probably mix easier if you fritted the glass first as Pete suggest - but I have had good results by just mixing it with the cullet as is. I was using a top fired gas melter.

Pete VanderLaan 03-04-2006 01:02 PM

I like to fine frit it because it allows better penetration of the cullet. You already have one strike against you since the glass is already formed as opposed to batch where you can really penetrate the structure. Cullets are frequently in an oxidizing state which limits you in coloring but persistence will yield some good stuff, not as good as batch and you can't make opaques but you can do a lot. Further cullets are normally not the most expensive glasses to make in the world, 4C being a good example and the lack of heavier alkaline fluxes limits tonal colors I find attractive but I would point out that all of Josh Simpsons work is done in 4C including the basic color. Peet Robison was making a copper ruby using fine frit at one point.We spent a good bit of the color class making a gold ruby batch that would be compatible with Josh's clear. I won't go as far as I go in the color class, it just isn't possible but I think we can improve your pallet some. Just make sure you get the crucibles from me.

Pete VanderLaan 03-04-2006 03:32 PM

I have a little time right now since I'm cooling my heels babysitting the gallery:

I am going to think in seven pound quantities heres since most of my old cullet formulas were based on a Tamax crucible that held... 7 lbs.

Most colors do pretty well in the one tenth of one percent amount there certainly are exception If I wanted to make a turquoise blue in cullet I would add about 25 grams of red copper to the frit. I think you could go up to 32 grams with no expansion shift at all. Fire in a neutral atmosphere.

The same would apply to Nickel oxide. It will make a purpley brown glass depending on the alkaline flux. I would bet that the 4c is cheap and the flux is soda so expect the brown tones. Again 32 grams.

Iron glasses. Ick... Some people like them. Add 20 grams red iron to the frit. it's coke bottle green. Try variants with a bit of cobalt or copper or both.

Try one gram cobalt and 30 grams copper. that should yield a periwinkel. You can mess with this combo endlessly.

Three grams cobalt is a dark blue for the absolutely uninitiated. Go to thirty grams and you will have a threading color as well as a trashed pot. Being in the crucible biz, I think that's just great.

Try 4 grams silver nitrate and 20 grams black tin and ten grams red iron. Reduce this stuff heavily. Beautiful opal swirls

try 20 grams copper oxide, 20 grams of black tin and reduce while melting. IF YOU ARE LUCKY this will make a red glass. I don't know enough about c4 to know for sure.

Chrome... it's hard to get potassium dichromate these days. No one wants to ship it. If you can get it, grind it finely and add 30 grams to the 7 lbs of cullet. Think 7 up bottles. Add cobalt or copper to change the blue tones. You can do some very nice and some very ugly things with this stuff. Aviod chrome oxide. It's very hard to melt. It's also carcinogenic. Think rat poison. That's it's claim to fame.

Neodymium oxide. It takes a lot. About 50 grams in seven pounds for a color that is violet in ultra violet light and ice blue in fluorescent light. This is not a casing glass.

Manganese dioxide add about 65 grams of this to the 7 lbs of cullet and see what it does. If it's too light, add more- maybe another 20 grams. It will kick into a strong purple. Tends to be messed up by high sodium base glasses and is gorgeous in potash glasses. You could add silver to this stuff too.

In general, ty to add the colorants to a slightly damp frit and shake it or whatever to get the cullet coated. Try to avoid dumping the chemicals onto the top of the cullet. This tends to sink to the bottom when the melt gets going.

For now, that should do it. You can't make opaque glasses with cullet. Forget cryolite and phosphates. Also don't add selenium to cullet or zinc. They won't work This however should keep you off the streets and amazing your friends for a while.


Peet Robison 03-04-2006 04:09 PM

I would not use Manganese with cullet. I don't think you will ever get a strong color no matter how much you use. I consider cullet "reduced" in the sense that there is very little O2 left in it. Manganese needs O2 to be purple. This was the reason using cullet for copper reds works fine if you don't mind the swirls.

Pete VanderLaan 03-04-2006 04:32 PM

Josh Simpson gets all of his purple color from manganese in 4C so I am quite sure it works fine. I did some work on that color for him in January so I know what's in the cullet additive. It has lots and lots of manganese and I melted it in the 4C. Any other suggestions will be greatly appreciated.

Peet Robison 03-04-2006 04:47 PM

My experience was with the SP87 cullet. I don't know what the difference would be but obviously there must be something. What %/ wt. was used?

Pete VanderLaan 03-04-2006 05:50 PM

about 2%. Sp doesn't take manganese well at all, you're right. Also the slightest amount of selenium and it goes beer bottle brown.`

Peet Robison 03-04-2006 07:31 PM

That's amazing! I use 2% MnO2 for a deep purple in sp87 BATCH but in cullet it doesn't do much at all. I just assumed the O2 in the batch kept the Mn oxidized. Was there any other possible introduction of Oxygen such as nitrates in the melt?

Pete VanderLaan 03-04-2006 07:37 PM

no. I can't talk about the additives too much since it isn't my intellectual property but I'm comfortable describing the manganese.

Dave Bross 03-04-2006 08:19 PM

Good work Kevin! Always question what you're being told are the limits.

A bit of potassium dichromate in with the manganese will do wonders for keeping the manganese in the state where it shows color. All my notes and books are packed up at the moment, so I can't supply a number, but I think Scholes lists a percentage for this addition in the color chapter if someone has their copy handy and can check.

If you want all your chemicals in one place at reasonable prices then check out:

They don't care what they ship.
They just added an annoying flash page as an entry. I hate that.

Pottery supply places will have a lot of these chemicals at higher prices. Davens Ceramics in Georgia is good and the prices not too bad.

There really is a huge range of blues and greens available by just changing the ratios of copper and cobalt. Some nice turquoise in there.

Different amounts of cobalt added to the manganese can give you a bit of a range in your purples too.

There's always sugar to get enough reduction for copper red, assuming getting the black tin is a problem.

A bit of copper in with cobalt gets you some different blues.

Pete VanderLaan 03-04-2006 08:26 PM

Manganese is really easy to "blow out" as a color in even mild reduction. In cullet that isn't hard to do. In batch it's much easier to retain the material. Even so, something in the 4C helps retain the oxidizing condition.

03-04-2006 08:36 PM

Peet, If you were using the color base batch, there would be no antimony. The clear batch definitely has some but is not as loaded as some clear batch. Antmony acts as an oxygen scavenger in cooling so it can counteract manganese. Manganese acts as its own fining agent since it releases some oxygen on heating and absorbs on cooling.
The results with manganese in cullet can depend on how depleted the oxygen is from melting. Quick well controlled melts might give cullet with better results than long overheated melts.

I think that if you are making cullet to use particularly for making color that there is no reason to go through an entire melt cycle. Get some of it melted, scoop it into water for making good frit. Then finish charging and make a good clear melt.

Pete VanderLaan 03-04-2006 09:15 PM

I just want it hot so it frits well.

Henry Halem 03-04-2006 10:49 PM

My experience with Manganese is that it is fugative and needs to be worked as soon as it fines. The hotter you get it the faster it burns out. It tends to sink to the bottom of the pot. It is phototropic, that is, it will deepen in color somewhat when the piece is placed in the sun. Those are notes from the dim dark past. Use the carbonate or dioxide and you get great purple foam and you can make Lava glass.

Peet Robison 03-05-2006 12:55 AM

It would make sense to add Potassium Dichromate as that would add oxygen to the melt. Cobalt carb would help also. My point was Manganese alone in cullet would be very difficult to make a dark purple since it needs oxygen.

Kevin Bethea 03-05-2006 04:12 AM

Yeah, I am not looking for the secret to anybody's color combo and I am not going to go into color production or anything like that. I'd just be happy to have more than 2 colors and I'd like to learn a little bit while I am at it. I looked in one of the mixing buckets while I was up there for 14 hours today and they aren't even going for the little chunks of cullet so I will make sure I pile up on the fritted cullet. Our directions are to add one spoon of cobalt to the bucket but everybody adds 2 spoon fulls and then lies to our teacher about what they are doing. I can't count the number of times people have asked where the spoon is. We have scales so I won't ask how many spoon fulls I need. There's only one person that mixes black and I haven't found out what he uses yet. He graduated but came back due to Hurricane Katrina but I haven't seen him to be able to ask him. I will keep notes and samples so hopefully I can get the results I am looking for eventually but there's not much that I could pull out of the pot that wouldn't make me happy. I know I am limited with the cullet but that's what I have access to for a while. I had a good idea while looking around the ceramics studio and decided to look for the pottery chemicals and found manganese dioxide and FeOxide black. It's the same instructor for both studios and he lets us do just about anything we want so I should be good there. I'll get what I don't have and I'll check out Dave's source too. I guess since I am back in school I feel like I should question things and this is something I have read about and followed on here but I had no way to try it. It has interested me for a while. Clean pots are probably necessary too so I need to buy a few small ones. I know there are lions, tigers, and bears along the yellow brick road but if it were easy it wouldn't be fun. Besides, it sure beats regular homework. I think you gave me enough to get started with listing what oxides give different colors for 7 pound batches. I don't know how many pounds they fit in the mixing buckets but 7 pounds sounds like a good place to start. Thanks Pete. I made my first encalmo bowl today and a teapot and the rest of the time I was just assisting one of the advanced students with different things but he doesn't know about the color stuff. It's kind of sad to me that not much is going on in the studio right now really but all I can do is just work to make it better. I wrote down what was written on the boxes that the stuff is stored in so I am going to list it in case what I need isn't really what I have. I probably have enough to get me in over my head in a hurry but I am willing to experiment and mix to see what I get. If nothing else I'll share my misery and we can all get a good laugh when things go horribly wrong. thanks for the help.
Kevin Bethea

here's what I found that we had in the store room. I wrote down what was on the boxes it is all stored in. I know most of this is just for glazes and won't be used. We have stuff to melt batch too from what I found but I figured I woud list everything.:

red iron oxide
mang diox granular
mang diox 200 mesh
chrome oxide
FeOxide Black
CoOx cobalt oxide
NiCO2 nickel carbonate
FeCh Iron Chromate
CuCO3 copper carbonate
SnOx Tin Oxide
dr. Rutile
lt. Rutile
Illmenite gran.
Crocus Martis
Yellow Ochre
English China Clay
volcanic ash
soda ash
Tit Diox
bone ash

Pete VanderLaan 03-05-2006 08:32 AM

you can use :
Crocus Martis ( spanish red iron)
Soda ash
red iron oxide
mang dioxide 200 mesh
cobalt oxide
nickel carb
iron chromate ( makes green)
chrome oxide ( hard to melt)
black iron
copper carb
tin oxide only if its black and probably is white.( stannous vs stannic oxide)

the rest is either clay stuff or won't go into cullet. wet the frit very slightly with a spray bottle and add chemicals/ You are but the latest generation to try this. Have fun.

Kevin Bethea 03-05-2006 10:14 AM

Thanks again. My teacher hasn't been blowing glass very long and he was a student of a professor that recently retired that had built the furnace a long time ago. He was a 70's type guy for sure so I imagine he knew about more than 2 colors but somehow that all got lost. His name is Ralph Harvey but I missed him by a few years. I know he has notes somewhere so that's my first question for him when I meet him. My teacher now has a background in metal working so we sometimes learn the cave man approach to glassblowing. No offense to cave people. It's funny to watch his demos sometimes. I have a lot to learn so I can learn a little of the good from everyone. Last night we were making compotes(sp? big goblet shapes), triple cup reverse axis vases with lip trails and matching handles, and various other bit work stuff. Taking some of the flashes made me nervous but I had fun and I got my workout for the day. Our studio used to be full all night long years ago but those guys have left and it's just me every night. If somebody does show up they are going to stay longer than they planned. I made sure I learned how to shut down first thing so I could be up there as long as I wanted. I get so excited I forget to eat so I can imagine most of you guys remember those days. I leave my phone number up there so if I am not there people can call me and I meet them up there to help out. I think I average about 60 hours a week on top of class time and I'd like to be there more but I have 2 other studio courses. Periwinkle sounds like a good color to start with but like I said, anything would make me happy. We have a sandblaster so things can be "fixed" so to speak. Thanks for pointing me in the right direction. Soon I will ask questions and eventually get to where I need to just take a color class so I have to keep hoping that you keep teaching it and that I can afford it when you do. After that I might be able to get something out of Weyl's book that I bought a while back. Basic guidelines are a great start for me. I heard Dave reference Scholes but is that a book or just research that's still accessible somehow? I doubt I'll understand it right now but I wouldn't mind buying another book. I know Dave has tried all kinds of melts so maybe one day I'll have enough notes to share. I guess I could make things that don't match the base at all as long as I don't case over it so I doubt anything will go to waste but it will be a while before I try opals and all the fun stuff I have read about in Dave's testing. For now, I am a happy glassblower so thanks everybody. I'll try the turquoise Brian mentioned I'm sure and we even got Peet in on this one. And no, I don't mind the swirls one bit. You should have seen the "successful" melt of red I saw. I saw 10 shades of brown I had never seen before and I wouldn't call it red if you asked me to name that color. When I want pretty red that will polish perfectly I'll buy Pete's. Same goes for the black since I have heard that stuff it just awesome. Thanks Pete and everybody. I'll be amazing my friends before I know it.
Kevin Bethea

Dave Bross 03-05-2006 11:03 AM


"Scholes" is referring to the author of a book called Modern Glass Practice.

There are a couple of copies for sale currently on abebooks .com for around $30-40

I think it's out of print at the moment

This was a most helpful read when I was first trying to get my mind around how to do color. Simple and straigtforward.

When you get to learning batching you'll be glad to have this book too. It walks you through the math in a very straightforward manner.

Sounds like you're in a good position for some late night color experiments.

Don't ever hesitate to check back with us. We all dearly want to see more young'uns become capable of melting color.

You're always welcome to email me if you want. Nice to see someone with your level of motivation.

One question.....

Do you understand how the level of oxygen in the glass is going to affect certain colors? If not we should explain that for you. This is why your attempted red came out green.

Kevin Bethea 03-05-2006 12:00 PM

Thanks Dave. I remember looking for modern glass practice for a while but I found out it was out of print so I will get it from your source while the getting is good. Simple and straight forward sounds good. I usually read books with pictures so when I got coloured glasses I knew I was in over my head. I am in a great position for late night experiments so I'll set aside some time to try some stuff. We are tough on the pots too. Last week I spent a couple days pulling cobalt off the floor through a small hole in the side of the furnace. There was a cracked pot and people thought it just hadn't been charged so they just kept filling it and refilling it. Yanking the pot out was kind of fun but not something I would want to do all the time. It didn't seem to bother anyone else. what a mess that was.
Thanks for offering the help. I know you have done the research so you'll have all the answers when I am stumped. I understand that it needs oxygen but I am not sure how to add it. I would assume it means turn the gas down so that it's not reducing but if you have time to explain I am all ears because I know I am way off. I have read about valence changes, antimony, and the need for squeezes but I wouldn't dare say I understand any of it. If I had to make a more educated guess I would guess some form of nitrates might add oxygen into the melt itself. The guy that melted the red that turned green got so mad at me for saying it was green but it was coke bottle green with a thin thread of something in the middle that he swears is red. That green looked better than the green that used to get melted when I compared some cane that was saved from both melts that I found last night. I guess that's why no one melts it. White would be a cool color to have but I will start small. Pete made Neodymium oxide sound like a lot of fun too. Another dumb question about the casing part. Does that mean I shouldn't case over it or I shouldn't use it to case over things. Probably neither huh? I'll keep filling up my skecth book will all the info I have gotten so far and I'll let you guys know what happens, good or bad. Maybe it'll bring back bad memories for some of you but it'll be good for a laugh. I might get lucky and get a red one of these days.
thanks for the info,
kevin bethea

Warren Trefz 03-05-2006 12:32 PM

track down Harvey

If you can you should track down the old professor Harvey. A couple of graduates from your studio who studied under him are now here in Cincinnati and they have talked about a bunch of colors that were made there. I have also heard that he sometimes still pokes around the studio. If you can not find him I will see what information I can gain from them on formulas or location of information. But also, as everyone has said good note recording and experimentation are excellent teachers. We use 4c here in Cin. but no color furnace currently, I would still be interested in what you discover. Keep us informed and enjoy!


Pete VanderLaan 03-05-2006 12:34 PM

when I say it's not a casing glass, I mean it is not an intense color than thins well.

Green is not a good color to find in your red. Pale blue, yes. Wheat, yes but not green.I usually associate that with having tried using white tin, not black tin. The former is an opacifier and the latter a reducing agent. White tin ain't gonna make a red. It does make insanely tantalizing streaks of red though.

"so you'll have all the answers when I'm stumped." hah! Maybe dave, not me. I will however offer condolences.

And, you aren't going to get a white out of cullet unless of course it's white cullet. Then it isn't going to fit.

Kevin Bethea 03-05-2006 03:40 PM

I've heard Ralph is still around and I asked my teacher and he said every now and then he pokes in the studio early in the morning. I have only been here a couple months so I guess I just haven't seen him yet. I know Ralph knows more than 2 colors but that was just what one of the advanced students told me. I thought it was kind of funny. I think it is just a lack of interest that caused us to be where we are right now. I heard he was a great guy but the way people talk about him it's like he died a long time ago with as many times as I hear "when Ralph was still here." If you want people to listen you just have to start the sentence with, "what Ralph told me to do was..." and people stop to listen. I know we had to have had somebody here melting colors because there are pieces all over the building with interesting colors. Ralph's notes are probably there somewhere too but I am willing to experiment on my own until I track him down. I am still finding new rooms in the building but I'll track down as much info as possible and experiment.
I understand the casing part now so I'll remember not to blow out the color on that one. I'll have to ask about the tin oxide we have. It may very well be white and that would explain the problem with his red. I know he added cream of tartar. I don't know what it does but he said it was necessary so he went grocery shopping before he tried it. I know white isn't possible now but one day I'll have a whole new ball game with batch and dangerous chemicals like Dave and I'll be up many a night just babysitting a melt while killing all vegetation in my neighborhood. Ok, so you guys might not have all the answers but I bet creative suggestions will be just as fun to try. We are on spring break right now but I will get Ralph's number from my teacher when he gets back. I have been looking forward to meeting him and he sounds like a helpful guy. I just have to hope he'll have time to talk. If not I'll just go ahead and try stuff and see what happens. I am a pretty good listener and I am interested in learning so we'll see how far that gets me. Getting things to fit is a whole different problem so I will just do testing. That's a whole class worth of info. we may have used different glass back then too. They switched from spectrum to 4c this semester but I don't know what they had before that. I just thought about that. hmmm...I'll find out. I ordered moden glass practice this morning so I will have some more reading to do. so far I know enough to possibly fix the red problem and I'll have room for one more pot so maybe I'll get the guy to try it again with my notes that I have so far and we'll try something new in the other pot. he's about to graduate so very soon I will be able to melt anything that I want to for a while I guess but I can use the help while he's here. I'll collect more supplies and read some more but when I get something you guys will know about it. I am interested in what you can get out of the guys in Cincinnati too Warren so if you have time I would appreciate that info too. I'll be here for a while so if they or anyone else ever happens to go past Americus Georgia they should stop by but it's not on the way to or near anything really. I think we're 3 hours south of Atlanta. We have 3 visiting artists that were past students coming in this semester and I hope to assist them as much as they let me so I can learn some stuff. I heard we might have to shut down for the summer if the class isn't large enough so I am kind of bummed so I don't know what I'll do if I can't get in there to blow glass. There are a few places in atlanta but that would get expensive so I will just hope for the best I guess.
Thanks again everybody,
kevin bethea

Pete VanderLaan 03-05-2006 04:19 PM

You should try to track down Frank Kulasiewitz in Valdosta if he is still alive. Frank was melting lead colors from batch back in 1971 which was just about unheard of. He published a book on glasmaking which is quite obscure. Henry didn't like his book much and had safety issues with it. Frank was something of a "free spirit" when it came to code but he was out there doing it outside of the university system. He would be in his seventies now at least.

Ted Trower 03-05-2006 05:05 PM


Originally posted by Pete VanderLaan
You should try to track down Frank Kulasiewitz in Valdosta if he is still alive. Frank was melting lead colors from batch back in 1971 which was just about unheard of. He published a book on glasmaking which is quite obscure. Henry didn't like his book much and had safety issues with it. Frank was something of a "free spirit" when it came to code but he was out there doing it outside of the university system. He would be in his seventies now at least.
Obscure, but not unavailable:

Kevin Bethea 03-05-2006 08:21 PM

with the periwinkel you said to try one gram cobalt to 30 grams of copper. When you say copper you mean cuprous oxide(red copper) and not the copper carbonate that we have already, correct? I am pretty sure that I need the red copper but I wanted to double check so I can add it to my notes.
Kevin Bethea

Dave Bross 03-05-2006 08:36 PM

Pete liked the concept of me having all the answers!!!!!!!

Actually, Pete was the one who taught me all the basics and he knows a hell of a lot more than I do.

NO ONE has all the answers 'cause we still haven't even found all the questions.

Back to the concept of oxygen in the glass.

The oxygen has to be chemically combined with the glass to affect the oxides you use for color. In glasses that want oxidation for color you add more oxygen.

The oxygen has to be cut way back in colors that want reduction.

If you are going after a color that needs a greater amount of oxygen to go to the valance where it shows a particular color, it's best to get that oxygen in there via one of the chemicals going into the glass.

If you have a color that wants reduction, then you have to start with a glass formula that doesn't have any oxidisers, and also add reducing agents like some form of carbon or the black tin for copper ruby.

In the case of your cullet experiments you want to put in enough reducing agent to reduce the excess oxygen that is already there in the cullet.

The old timey way of making copper ruby was to re-melt and frit the cullet a number of times to reduce the oxygen in the glass.

The potassium tartrate your guy was adding is a reducing agent, but he probably didn't get enough in there.

Try sugar for reduction in cullet. The sugar becomes carbon when heated. Old time glass melters would chuck things like grain or coal into a glass to get reduction.

The potassium in the potassium tartrate is also moving the expansion of the glass higher and that's not going to help when you try to fit different glasses together.

The furnace atmosphere has a much smaller effect on the level of oxygen in the glass than chemical additions do. You can't ignore it though, it can change things enough to screw them up.

You can use the copper carbonate to replace the copper oxides in most things, you just have to do a little math to compensate because the carbonate has less percentage of copper in it. Here's a pretty good on line source for the percentages in materials:

Pete VanderLaan 03-05-2006 09:10 PM

on the other hand copper carb is chock full of oxygen which doesn't particularly bother me since I tend to overwhelm it with stannous oxide. Do not think that stannous and stanic sound so much alike that they should be interchangeable. They aren't. Your white tin won't work.

I think starting with red is not the best plan since it's a very toucy color to achieve. Better maybe to start with the simpler stuff and just become familiar with the processof mixing and melting first..

..and there isn't that much potassium in tartar sauce. I think the formula is KNa2C4O6.4H2O so it's sort of a mixed bag I think I remember that since I was sending some to Mark Peiser two days ago and I actually bothered to read the bottle.

Kevin Bethea 03-05-2006 09:35 PM

I'd be really happy if I got into this enough to have questions that you guys couldn't answer but I think we are safe on that one for a while. I know I could really mess something up but the answer to that question is to try it again and see what happens and keep notes. I'll understand it more as I get into it. I thought I understood about adding the oxygen but it's more important here to remove it for some colors. It makes a lot more sense now. Now I know what the cream of tartar does. I'll have to ask how much he added. How much sugar would I stick in with the 7 pound melt to replace the 20 grams of black tin? I saw a box with SnOx tin oxide on it but I think it might be white and not black but I will ask. Is it a one time thing or do you have to keep adding sugar periodically as it melts? remelting the cullet sounds like a good way to remove the oxygen too but adding sugar is a lot less work. Thanks for the reference for the percentages. I'll figure it up and make sure I bump the number up a little bit for the periwinkle. my book should be here in a week or so so thanks for that link too. I guess that would also work for the opal swirl too but I need get the silver nitrate first. Pete said to reduce it heavily but does that mean reduce it while it is melting or in the glory hole to get the swirls?
thanks for the explaining all that,
Kevin Bethea

Kevin Bethea 03-05-2006 10:04 PM

Pete and I were typing at the same time and he beat me to the post button. I bet the extra oxygen would mess up the opal swirl so I should just wait until I get the cuprous oxide for that one too. I don't think starting with red is the best idea either, I was just thinking we have a pot for red already and I might can get the guy to try it again with sugar if we don't have black tin and kind of learn from that. I'll try the purpley browns, blues, and greens and then maybe I will have some success with the periwinkle and opal swirl whan I know more about what I am doing. I was blowing when I heard the guy remember out loud that he almost forgot the cream of tartar. I thought he was kidding but he left to go to the store. I had to go to class so I missed him when he got back. I missed it when he added it to know how much he used. I heard him shaking the bucket when I was working so I missed it when he mixed the other stuff to add to the cullet to know what he tried. I'll see him soon and I'll ask him as much as I can to see what there is to gain before he leaves. I am soaking it all in and we'll see what happens. thanks for the nudge in the best way to gratification. I know what you mean.
Kevin Bethea

Dave Bross 03-06-2006 01:07 PM

Extremely good chance you will get to experience many, many, of Pete's condolences if you go after the red, but, then again, if you get it, you've accomplished something major.

I sound like a used car salesman.


I'll give you some suggestions and then you get to late night experiment until MAYBE you get something that will work.

First problem....gotta have tin with the copper for it to go red gracefully. It can be white tin but then you need something else to take care of reducing the oxygen. Pull out your copy of Weyl, read page 343, read pages 420 thru 432. Rough rule of thumb, start with equal amounts of tin and copper.

The problem is that the tin doesn't want to melt. Hence the streaks Pete mentions. Other than mixing it up with lithium or some other alkalai, which will move the expansion up radically, your best way around this may be high temps for melting. Note: you can always bump up the expansion of your clear cullet with a bit of alkalai to match expansions if you absolutely have to have the lithium to melt the tin in the ruby.I've also thought about using stannous chloride for the tin, but the chlorine would cut back on the "pretty" in the glass and we're talking expensive chemicals again with stannous chloride.

Second problem.....Reducing the oxygen. Black tin really cuts down on problem one and two, but let's see if we can get around having to use it because it's VERY expensive and hard to find.

Sugar used as a reduction agent in copper ruby batch without oxidisers is used around 5 grams to 20 pounds of batch. Thank Dudley Gibberson for that number. Using cullet, you will be fighting oxygen already present in the glass so you will need more reduction.
To give you a speculative maximum number, you can theoretically make an amber glass from cullet by reduction only, using 18 grams of sugar per pound of cullet. Thanks to Rollin Karg for this amber recipe. This will be a "test and tune" situation. If you reduce the glass too far you get livery colored glass, not enough reduction and you get no red.

Ok, I'm done yelling now.
The way antimony is usually used is as a fining agent. It changes valance as you come down from cooking temp and sucks up large quantities of oxygen, which were put in there originally by the nitrates and other oxidisers in the batch.I'm sure you see where this is going. Putting more antimony in with the already melted and fined cullet sucks even more oxygen out of the glass, making for reduction. Thanks to Rollin Karg, I actually have an antimony reduced cullet recipe:

20# cullet
1# soda ash
17 grams antimony
45 grams tin oxide (white tin)
45 grams zinc oxide
45 grams red copper oxide

Antimony in this quantity in a clear glass would discolor it yellow-grey, but that could actually help the red color a bit in this application. The grey may detract a bit from the "pretty".

Problem number three is to get it to fine out. High temps to reduce the glass viscosity so the bubbles can rise is probably your best bet. You can't use the traditional nitrate/antimony combo in reduction glasses because of all the oxygen in the nitrate, and antimony by itself doesn't do much towards fining.

Pete VanderLaan 03-06-2006 01:39 PM

Tin Chloride will work much better than white tin. The material should break down to SnO and CL which will help with the fining. If you start with white tin you already have two strikes against you. It is not very soluable at all. The Chloride aspect may induce livering. Better to me to start with the right materials.

Dave Bross 03-06-2006 05:33 PM

So very true, but, black tin is impossible to find in small quantity. I would love for someone to prove me wrong on finding small quantities.

I've still got a good bit of what I got from you. I never could find it otherwise, short of a 45 pound drum.

I think that when I get up and going again I may buy the drum of black tin anyway.

With the price/availability problems of selenium, it's looking like a very good time to develop higher skill in copper ruby.

Pete VanderLaan 03-06-2006 06:20 PM

I sell black tin at 15.00 lb but I won't sell less than 100 dollars worth. Some things aren't worth packing amd I'm busy.

I was under the impression that Seattle Pottery sold black tin at it's normal usurous rates but I don't know that for sure.

I just can't equate the color from Cad/Selenium to that of copper Ruby now that I melt the Selenium regularly. It's a lot like life after you've gotten laid for the first time. hard to go back.

Scott Novota 03-06-2006 06:58 PM

Am I to understand that if I drag my happy ass up there I can get some free blow time with you?

I have been looking for a road trip.


Dave Bross 03-06-2006 07:41 PM

I suspect copper could approach or surpass the selenium reds in the right overlay situation. All by itself, no. Although I wonder what might be done based on the recipe in the archives here that combined silver with the copper ruby. The silver yellow might be a nice color tone addition to copper red.

Charles, Barb, Rich and I saw a copper ruby vase in the Tiffany show that we all declared our favorite piece without input from each other. Wet dream red like we've never seen before.

That's good to know you're still game to sell some black tin. If anyone else wants some and can't swing the $100 I'll go in with you. I still have plenty but I'll offer that in case it's needed.

All times are GMT -5. The time now is 03:21 PM.

Powered by vBulletin® Version 3.7.2
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd. Opportunity Network. 2008. All Rights Reserved.