Clay & Glass

[Patsu]

...

[Matt Oz]

If anybody knows it's this guy, looks like he likes to help people out.

 

John Groth fused glass and clay

[soilandpolish]

It looks to me like he's about the patent at the moment, it's mentioned in the second sentence of that page. So he may be willing to tell you how to do it (I think that's highly unlikely though), but if his patent goes through you won't be able to use the info without his permission. And if you figure it out for yourself, you still won't be able to use it, that's how patents work to the best of my knowledge, so ... yeah.

 

Not that I think he does wrong to patent, per se, but let's call a spade a spade.

 

Andrew

[Benzine]

I'm not very knowledgeable on the material/ process, but would Egyptian paste work?  I've seen there are formulas that go as low, as at least Cone 010.  Would that still be too high, for the glass?

[Matt Oz]

What you need is a clay that has a matching COE (coefficient of expansion) to the glass, It could be a low, mid or high fire clay and already fired to its temp, then you could fuse the glass to it at whatever temp the glass needs. The hard part is matching the COE. I don't know what clay to recommend though. I thought that guy might sell you some.

[soilandpolish]

This topic really interests me, wish I had more to suggest.  If you do try any experiments, I hope you'll share your experiences back here Pazu.

 

Benzine and Matt make some promising suggestions.  Like Matt says, if the clay is already fired to maturity (and it and the glass have compatible thermal contraction), you only need to heat the clay the second time up to glass fusing. I wonder if you could join them by hand at that point? Or with something like the Egyptian paste as a slip to help mediate them? Maybe you have some fragments of the antique glass that you could grind to use in that.

 

I hope some others with more experience will add to this thread.  I have to admit I have no experience at all.  But I've been thinking about trying this, in the context of experiments with mixed/layered materials, graduating and weaving between ceramic to glass like rocks do. Though it doesn't seem really pertinent for your situation Pazu. And you probably do right to join them with an adhesive at low temperature.

 

I hope I'm not annoying anyone with my long post out of ignorance, but I'm enthused, and my last post didn't really address that... 

 

Andrew

[Matt Oz]

It's always fun to experiment.

[trina]

Have fused stain glass to pottery, however I always use it as kind of a second glaze, if that makes sense. How do you imagine the stain glass to be connected to the clay? Just to help me imagine the effect you want. Matt is right its tricky to find the COE but do able. T

[trina]

I like the idea of these light collectors, I am not sure if I would worry too much about how you make the connection between the two pieces. If you are using stain glass you could just glue them in and then maybe fill any gap with copper foil or something gold leafy ect... Plus I think you will find that, that type of stain glass will already start slumping at 650-700C. T

[Bob Coyle]

I'm not sure the aesthetic gain you would get by actually fusing the base to the stained glass would be worth the effort. I fact if I were to do  a base, I might just leave it raw fired clay with no glaze or a dark slip.

 

I have worked with several glass artists to produce forged metal bases for their pieces. My thought is that the prototype bases you pictured are too small. The glass would be prone to fall over with the smallest bump.

 

Some of the bases I designed were actually hollow with metal bars welded inside to counterweight the tall glass pieces.

[Bob Coyle]

The people I worked with were pretty reluctant to have my work with metal, detract or conflict with their work with glass.

 

I originally wanted to do some more elaborate metal pieces that I felt would compliment what they did. My ideas got a resounding thumbs down. They did not want the metal base to be a focal point.

 

Since it was their dime... I went along with what they wanted. I gave them a minimal base that had just enough metal to make it stable and follow the summitry of the piece.  In your case, you will be creating both, so you can make the base a second focal point of the piece if you want, but what I found was that they were correct in keeping my contribution to a kind of functional minimum that simply followed their lines without advertizing itself.

[deborahl24]

As a glass artist just starting to work with paper clay this subject is of great interest to me. I notice you mention stained glass , is there a reason you want to use stained glass or are you using it as a generic term for all glass?

I have been successful using COE 90 fusible glass frit directly on clay at full fuse temps and slag glass, COE unknown first fused to abstract forms then fused to paper clay at tack fuse temps. That is still in the experimental stage to find just the right temp. to get the two mediums to fuse without losing any of the forms.

I would be very interested in sharing any information that could be of help. I have to admit I don't understand a lot about clay but I have a wonderful mentor who is very knowledgable.

[LovesPurple]

I am on the same page as deborah124.  I use paper clay and glass.  I have been very successful with using glass frit on cone 04 bisque and firing it to cone 06 by sprinkling the frit into wet glaze.  The biggest problem I see with what you are trying to do is the low temperature where glass slumps.  You need to get the glass hot enough to liquify to fuse to the clay, but that would make a complete puddle out of your entire piece of glass.  If I were going to try what your are attempting to do, I would do a full fuse of the frit onto the clay, which I have done at cone 06.  Then I would take the piece I wanted to attach, find a way to keep it parallel to the kiln shelf, and then use posts, globs of clay, or whatever to keep the base on it's side and firmly up against the glass piece - then I would do a tack fuse (<>1325-1350° F).  Glass slumps before it tacks so you would need to support it right up next to the base.

 

I use Laguna's Max's Paper Clay and COE90 glass.

[PeterH]

For what its worth, this may be the patent

 

http://tinyurl.com/ljex2hv

 

Regards, Peter

[Bob Coyle]

Interesting link Peter. Looking at some of their percentage ranges of metal oxides, you should be able to derive a limit formula and tweak your raw materials to fit.

[BonnieMc]

I had been experimenting with fusing glass in/on clay for a while when I ran across a link to John Groth a couple of years ago. He said he had been experimenting for 11 years (!), he'd formulated a clay with compatible Coe to fusing glass, and was in the process of patenting it (as noted above). However I haven't been able to find any mention online of the clay itself for sale. Funny, I've gotten so used to just Googling to find products that I'm embarrassed to say it has only now finally occurred to me to contact him directly! I will report back what I find.

[Idaho Potter]

Okay, I'm confused with the phrase "stained glass".  Stained glass--to me--means either lead kames and/or copper foil and lead soldering.  If you are talking about that, the lead is the loser here.  You probably don't want fumes from that in your kiln, and the fact that lead melts around 400 degrees makes it worse.  IF--on the other hand you are using  the phrase to denote various types of glass, then the slumping point varies depending on the glass itself. 

 

I've found a glass blogger and newsletter "Hot Out of the Kiln" covers glass pretty well and they share well with others. 

 

I use glass rods and chips as part of the process on the outside of decorative work.  I work the clay as usual through the glaze firing, and then come back at the lower temps when adding the glass.  Really need an electronic controller so that you can do a slow ramp and hold for annealing the glass so it won't shatter. Seems like lots of homework before you successfully integrate the two mediums.

[BetsyLu]

Hey, I don't have a lot of experience working with clay, but I do have quite a bit of experience working with glass, and there are a few things you need to know about: 

 

First, I'm assuming you know the meaning of the term COE, so I won't go into details here (if you don't, google is your friend!)

Anyways, different kinds of glass have different COEs, and thus different firing schedules. Generally if you are doing kiln work with glass, you want to use glass formulated for it. I recommend the Bullseye brand, with a COE of 90, or you can use Spectrum glass with a COE of 96. The firing schedules are different for each kind, so it's important to know the COE of the glass you're using (which makes using found glass a little tough because it's a LOT of trial and error)

 

Secondly, glass has very specific firing schedules. You have to heat it up slowly so it doesn't crack on the ramp up, and you have to anneal it, which means you have to cool it down very slowly so it doesn't crack or lose its strength. Even if your glass survives a firing without the right annealing schedule, it's likely to crack down the road... you can't depend on it to hold together forever. I've had glass that I thought was fine just randomly explode a couple of months later. It's very temperamental. 

 

Thirdly, you can absolutely slump class over a bisque-fired ceramic mold. In fact, I often use unglazed ceramic plates to slump over to make glass plates. The important thing to remember is that the COE of the clay and the glass will be different, so don't let the glass slump in such a way that it creates a mechanical lock around the ceramic piece or it will crack or be weak. Think of it this way: you have to slump it in such a way that you can lift it off the ceramic piece easily after firing. I'd suggest slumping over and then gluing on after, using some kind of glue that can fill gaps (maybe even silicone?) 

 

I hope these tips help a little, feel free to message me with any other questions! I do want to stress that it's important to follow a very specific firing/annealing schedule when dealing with glass if you don't want cracking/shattering/exploding... and the schedule depends a lot on the kind of glass you use and what you're trying to do. Tests are your friend!  

[JackieRM]

Although I am new to ceramics, I love the idea of fusing the two together. I have experimented with various types of clay and glass. the one I find that works the best (at least for me) is bullseye glass (finely powdered and and added dry). I'm still working on getting the annealing times right but hopefully it'll only be a matter of time. This example is of some terra-cotta clay with an 'off the recipe' glaze, bullseye frits, a teaspoon of china clay and a sprinkling of Cobalt DiO2. Like I said, still a work in progress.

[JackieRM]

I thought that it might have been a more common practice than it is.

 

What I will probably do is model the clay and glass together in a way that is forgiving in terms of contraction, then separate them, fire the clay then bond the glass into it inside blind joins, with PC 11 or something.  As long as the joins were good fits the result might be aesthetically pleasing enough for someone to buy.  For instance, just a glazed stoneware 'foot', that holds a bare, diamond shaped stained glass pane, in a horizontal upright orientation.  This is old, I suppose 'antique' stained glass, which has its own unique appeal, that is what would carry the piece, the ceramic part would literally be a supportive role.

 

I have not yet determined the slump point of the glass.  With what I have learned here, it seems better to avoid attempting to fuse the two.  

 

It is on my list now, to experiment with Egyptian paste!  

 

Thank you all for the supportive advise - John

OK, here goes. the basics of a glaze are (as I'm sure you're aware) an alumina, a silica and a flux. the glass has the silica so it can replace the quartz or flint or whichever you choose to use. What I do is insert glass frit in a dry state, and mix a wet batch of base and apply. Using colourant (in my case Cobalt DiO2) and firing slowly to the glass temp. Most stained glasses have a slumping temp of around 800 degrees and a melting temp of 847-900. The clay I use for this is pre-biscuit fired Terra-Cotta as it is a relatively low fired clay. The annealing temp should be brought down very slowly to allow the glass to fuse to the ceramic vessel. There is a book on glass slumping featuring glass slumping and ceramic mixed media that may prove useful written by Joy Bosworth that can be bought very cheaply online. Hope this helps.

[BetsyLu]

If it helps, you may want to research pate de verre. It is fine glass frit mixed with a binder (usually gum arabic) and made into a sort of paste, which is then pushed into a mold (usually plaster and silica). It may be a more forgiving way to incorporate glass, but it is a technique to master in itself. (I haven't done it myself, so I can't give any personal experience here.) 

 

I would recommend picking a specific kind of glass and sticking to it. Using glass meant for stained glass will lead to frustration, as each piece has a different COE and is thus incompatible with other kinds of stained glass. Plus you'll have to develop a kiln schedule for each individual piece of glass. I would recommend using one of the more expensive but more reliable brands meant for kilnwork- Spectrum has a COE of 96, and Bullseye has a COE of 90. There can still be slight incompatibilities but not nearly as bad as you get with "found" glass. One other thing to keep in mind, though, is that glass from recycled bottles has a higher melting point than these glasses do and thus might be better suited for ceramic work. It's tough to find a good kiln schedule for it, though. 

 

http://cdesigns-isr.com/docs/FusingSchedules_COE90-96.pdf

Here are some basic starter schedules for each kind of glass. You'll notice that the temperatures and time are very specific. That keeps the glass from getting thermal shock and cracking. There are 2 very important parts to how glass responds to heat: how hot it is, and how long it is held. 

 

Remember that you'll need at least a tack fuse to get the glass to stick to anything- at a slumping temperature it is not molten enough to bind to other glass or materials. Glass slumps before it fuses, so keep that in mind! Don't expect perfectly cut squares to stay put and keep their shape on a curved surface, for example.  

 

Hope that all made sense and is helpful!

[BetsyLu]

 

When mixing glass with ceramics, you need to understand that the COE needs to be converted.

 

For no good reason, Glass COE is measured in inches per degree C.  Glaze and clay COE is measured in meters per degree C.

 

So COE 96 glass has a ceramic COE of 2.44.

If I've done the math correctly, 96 x 10-6 inches per degree C, is 2.44 x 10-6 meters per degree C.

 

Here's how COE 96 glass compares with other ceramic material.

 

COE Expansion

7.86    Zam Celadon Glaze

6.99    New Zealand Frost Clay (Laguna)

6.74    Oribe Celadon Glaze

5.60    Hagi Porcelain (Laguna)

4.64    Amador Clay (Laguna)

2.44    Glass COE 96 - This intentionally shivers inside a New Zealand Frost orange slice.

Adjoining COE 96 glass is made into ceramic compatible sauce, without shivering or crazing, by mixing with high-expansion Ferro Frit 3195.

 

Have fused stain glass to pottery, however I always use it as kind of a second glaze, if that makes sense. How do you imagine the stain glass to be connected to the clay? Just to help me imagine the effect you want. Matt is right its tricky to find the COE but do able. T

 

 

Really good info there, thanks for sharing! Do you know if there is a way to lower the COE of ceramic so you don't have to add anything to the glass? (I'd presume you'd have to use glass powder or fine glass frit to mix anything with it, and for those people who want to use sheet glass it might be interesting to adjust the clay instead?)