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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!


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