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I'm starting a new thread on firing glass on clay. This subject has been brought up on this thread and I thought if we are going to discuss this further we could do so here to avoid digressing too far from the OP's original question in the above thread. I'm going to start this thread off with this post from @Chilly :

"It terrifies me that you sell stuff that you know splinters.

I really don't understand using glass with clay.  To me it's like putting diesel in your petrol-engine car, just because they both came from crude oil."

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Usually looks like broken glass to me, kinda sounds like it's just as dangerous too.  I'll stick to glazes haha.  The problem with making something dangerous and selling it with a disclaimer is that the disclaimer means almost nothing to a large swathe of people and if it's gifted or resold, that disclaimer has a very low chance of making it to the next fella.  

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Is this the stuff with a pool of clear glaze at the bottom of a bowl? Just looked at the original post & that's what I thought it was. Too bad it splinters!

 

Edited by terrim8

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Firing glass on clay is aesthetic but almost certainly not durable. Now do you feel comfortable creating art that can be handled but features a beautiful assortment of exposed razor blades?  Likely not and perhaps an unfair comparison but I am personally not comfortable with it and If I chose to do it would likely feel obliged to encapsulate it for safety. Maybe glue it  inside a glass cloche!

I see this as risky, so in my opinion - I am not in favor of it.

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34 minutes ago, terrim8 said:

Is this the stuff with a pool of clear glaze at the bottom of a bowl? Just looked at the original post & that's what I thought it was. Too bad it splinters!

 

Just a general question about how people feel about firing glass on clay, could be recycled glass, beads, frit, noodles, pebbles, stringers or any other form of glass.  We don't know if the image in the above mentioned post splinters, it was another member who spoke of glass "splinters".

Couple images I pulled from online to give as examples to anyone not familiar with this look:

image.png.dee1f50aa1ae5372bd99c08863e61d2a.png image.png.3ac1e47d654badeafa571509f2eb2e60.png

Edited by Min
added images and thought

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11 minutes ago, Min said:

Just a general question about how people feel about firing glass on clay, could be recycled glass, beads, frit, noodles, pebbles, stringers or any other form of glass.  We don't know if the image in the above mentioned post splinters, it was another member who spoke of glass "splinters".

True but it is the thing that comes to mind when most often I see pottery folks drop glass into their bowl or vessel and proudly fire it for the cracked glass look. I guess it could be well thought out and tested and made to look like the nice uniform melt of a glaze. Maybe.

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I started a thread on this topic a couple of years back when I was exploring this method. I spent some time reading up on the glass art side of this equation. I bought a book by Charles Bray: "The Dictionary of Glass and Techniques."  Soda glass is the most common glass sold in the glass trade: and the lowest COE of colored glass or frit is 9.00.  Porcelain and stoneware typically average. 5.50-6.00  COE: a serious difference. The crackle effect is the result of this wide COE differential: and cannot be controlled to any degree.I bought a small amount of colored glass, along with a fusion bonder commonly used in the glass trade: with very poor results.

Note: the frit used in glass arts is not the same as Frits used in ceramics. Ours is powdered, and theirs are ground chunks: meant for decorative effects. There is a potter in Japan mixing glass and ceramics successfully, stunning actually. From what I remember: she was either making her own glass, or having it custom made with much lower COE values.

i view it as: the potential liability far outweighs the rewards. Coming from a guy with a long history of pushing boundaries.

tom

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Everything about doing this is wrong unless its strictly a non functional piece of art.

I call that look broken windshield .

Nothing like a piece of glass in your coffee to round out your day. Better have a big insurance policy if you are making this stuff. Hey its  for sale on Etsy so it must be ok?right?

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Glass is only glancingly related to glaze and clay. There are some ingredients that are common amongst all 3, but think of them like bread, cake and pie pastry. They're all similar in that they're all baked and contain flour, but the proportions of other ingredients, the method of combining them and the temperature and duration they all need make a huge difference in the final product.

It's not a matter of if the glass/ceramic combo will fail, but when. Could be next week, could be in five years. As Tom already mentioned, the COE's of the two materials are too different. Phase changes that clay and glass go through upon both heating and cooling happen at different (and incompatible) points, so the clay and the glass are actually not really adhered to each other particularly well and all that pretty, fragmented, sharp glass will pop out eventually.

Additionally, a word on decorative and stained glass:

if you're using anything that's meant for stained glass purposes (and it's tempting because it's so pretty), you'll actually kill most of the colours at anything higher than lustre temperatures (022-017) because the colourants that are used are often organic, or will simply just vaporize. Even other common sources, like decor marbles will actually boil and begin to decompose significantly if they're fired even to bisque temperatures, never mind some of the glaze fire mentions I've seen. And decorative glass can use colourants like arsenic that aren't commonly used in ceramics, so we don't think of them as potters, but if they boil off in the kiln, you could be unwittingly exposing yourself to a host of things that are Bad For You.

Tl:dr: Just. Don't.  Please.

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Ok, Im the one who used the word "splinters" and let me clarify some about what I do, how I do it, and why I do it.

First, I may have made the "splinters" sound like a more chronic problem for me than it is; on occasion, if I use too much glass, the glass can splinter. The thickness of the glass being put into the dish does impact the amount of crazing, and I use very little (weight...maybe a few grams, size....maybe a  large chickpea?) I have seen folks who have flooded the bottom of their dishes with ounces of glass, only to find that their pot which will crack, post firing, right around that line of extreme stress in the clay body.  I am aware that the glass crazes because of the large difference in COE, and that the physical bond between glass and glaze/clay is weaker than that of glaze alone. I can, with my fingernail, feel the edges of the cracked glass, post firing, but rarely do I come across a splinter. Not to say it doesnt happen, but it is likely less than 1% of the work that I use glass on, do I find a splinter. I have never cut myself on any fused glass on a clay surface, and unless the glass was super thick in its application, I wonder if it would be even possible to have a large enough craze to have "razor blades" in the glass surface?

Aside from my own experiences, I have nothing to substantiate the following further;  I believe that the amount of crazing which occurs during the cooling of the kiln is the most stress the glass is going to experience, and thus, post firing, I am not terribly concerned about more splinters occurring. This would be unless of course someone was heating the ware well past its normal intended cycles (dish washing). To test this, I took pots with this glass in it, and stuck it in my dishwasher(used daily) for months, never taking it out, to see if I could notice any discernible difference in between it and another; I found no  further crazing, or degradation of the surface of the glass. Now, if someone were say, placing this dish into boiling water, then into an ice bath.....yea It probably would not look to great following that, however who in their right mind is going to do that?

Likewise, I do not believe, that give the life cycle of the pots of make (their intended life cycles) that the glass will just spontaneously pop free from the vessel. If it were a vessel that was undergoing regular expansion/contraction cycles, for years....decades.. I would be more concerned about the physical bond being weakened so, that it would break free becoming a major hazard. Yes, I will hear crazing occurring in the pieces in which I do use glass, for hours after the firing, but Ive had pots that I made using glass in them, nearly a decade old, and Ive never had a loose piece of glass come from it.

When I do use glass, I only use it on pots that arent going to be used for utilitarian purposes; Yes as liambesaw pointed out, the next fella could not relay the message that "this" was not to be used for food purposes,  which is why I dont use it on pots that "could" be used for food. Wine stoppers, drawer pulls, magnets and little dishes (like 2" in diameter" are practically all that I ever use glass on. Aside from these, there are some places, like the lid of a butter keeper, which never comes into contact with the butter, where I will use glass, or in the depression of a knob on a lid, but I never make vessels, which would be of any size/shape that someone could/would eat food from, which have glass on them. I agree, that it would be too easy for someone to inherit, buy at a flea market, etc to not know that this is not food safe, and I dont count on the general public knowing the difference.

For example I did come across a potter at A2 who was selling a double booth full of pots, every single one of them had a thick (like 1/4") layer of the glass in the bottoms. Everything from bowls to plates. Now all of his work was "meant" to be wall hangers, as noted by the wire in the foot, but every pot he sold could have easily been "misunderstood", taken off the wall, and used. I dont do this; I dont have "utilitarian" shaped/sized vessels that have glass in them...EVER! Yes, I guess someone could make a teeny tiny meal in the top of a wine stopper, but they could also make a teeny tiny meal out of a dish made from a chunk of lead; I cant predict or attempt to prevent every scenario which could involve a piece of my work and a customer; I do the best I can, but I cant stop someone from hitting themselves in their head with my pots.

I do use the glass because my customers like it, and I do enjoy the contrast in surface and color it provides.

I have no false pretenses that it provides a "better" surface, and am aware of the more real fact that it is a weaker surface, and generally "not as durable". I understand too that the amount of tension it places upon the clay not only makes a weaker surface, but physically could threaten the integrity of the vessel.  I want to make it abundantly clear, as this forum is visited by those who have lots of experience, and those who have little to none, that I am not advocating that you do what I do, just because I do it. If you visit enough of the postings, you will see, that I am always preaching safety in the studio, and safety with your pots. I am by no means the "all knowing" and have made mistakes in the past, however I do the best I can to eliminate dangerous situations, and if I have an issue, I do what I have to, to eradicate the issue. I believe that what I am doing, the way I am doing it, with the fused glass is safe, however I am not preaching that it is safe for any/all use. This kind of mentality falls under the same guidelines as those who use glazes which contain barium, only on the outsides of their pots, with liners on the inside; within limitations there CAN be safe practices, using "dangerous" materials. 

Like glazenerd did also, I researched the COE's of glass and clay to see if there was a combination of soda/lime, borosilicate, or pyrex which would have a COE similar enough that it would provide the color contrast, but not the crazing. I never could find a glass which was similar enough in COE. I had not heard of this Japanese artist blending their own glass; this is intriguing! Do you know who the artist is? I would like to learn more about this! My wife worked for a hot glass studio, and I like to play in hot glass; Ive been wanting to incorporate blown glass with ceramics, which as Ive been told by everyone in the glass world Ive met, is not physically capable because of the COE difference. (at least, for studio glass/clay artists; Im sure industry can do it)

So, I do hear all of you; the safety concerns about using glass in your work are large, no doubt! I use it in a way that I am comfortable with, and am not preaching that it is safe to use without limitations. As with anything in life, there has to be some common sense used; a circular saw works well to cut a piece of lumber, but Im not going to sharpen my pencil with it. 

In the other post the discussion about the crazed look: I was not advocating that the OP'er use glass to achieve the look they sought, simply that it could. I did not want to elaborate with the above information, since the post was not about this. I appreciate Min making this posting so there was a clear area where this information could be discussed without hijacking anothers' posting.

I apologize for any panic attacks I induced, or any confusion I may have created; this was not my intended purpose.

 

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@hitchmss, thank you so much for taking the time to elaborate on your process, outcomes and caveats. I was hoping you would chime in here to voice a point of view from the other side of the fence. It's wonderful that we can have a dialogue about this.

The Japanese artist I know about who is melding glass with clay is Misa Tanaka. I don't know what is meant by "melds".

image.png.c65759d0be1684e99d9f0c09b2d61ba4.png   

Edited by Min

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2 minutes ago, Min said:

@hitchmss, thank you so much for taking the time to elaborate on your process, outcomes and caveats. I was hoping you would chime in here to voice a point of view from the other side of the fence. It's wonderful that we can have a dialogue about this.

The Japanese artist I know about who is fusing glass with clay and not having the crazing issues is Misa Tanaka.

image.png.c65759d0be1684e99d9f0c09b2d61ba4.png   

Im more than happy to elaborate. I love and hate the online experience. It can be very difficult sometimes to describe, accurately, what you intend to relay. So much is lost between what you can say to a person, in person, vs what is said through text online. It is apparent that my post in the other thread was too short, and lacking information, and as noted above, I appreciate that you saw the need for further clarification, and like you stated, have an area where dialogue can be had.

Those vessels by Misa Tanaka are beautiful, and very much the same principles that I am wanting to achieve. A permanent physical connection between clay and glass. Ive been making these perforated vessels (lots of holes) that I want to blow hot glass from the inside-out so I can achieve a bubble wrap like look to them. Still not sure that I can do it, but this may be some very useful information!

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Phwee, thank you @hitchmss for your clarification.  I left a number of FB forums on clay after the continued insistence by some members that mixing glass and clay was "fine".

My first pottery teacher said:

"If it's shaped like it could hold food or drink at any time in the future, it should be suitable for food or drink now."

and

"whatever you make today, you have a responsibility for it's safeness forever"

and

"What you do with it and what your successors do with it could be very different."

 

I try to make sure my stuff follows her guidelines, and have great fun with the ceramic destroyer on any that don't after firing!

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1 minute ago, Chilly said:

and have great fun with the ceramic destroyer on any that don't after firing!

What is your chosen method of "destroyer" Chilly? Mine varies between a trashcan and shotgun, depending on time, and the amount of frustration.

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when I first  started using my own kiln, I was melting glass in the bottom of small "ring" dishes.  I would use broken wine bottles, stained glass, glass beads, whatever.  Like Hitch was explaining, I found out quickly that if I used too much glass, it would crack the dish, sometimes the glass would splinter. I was making a large bowl to be used for baptisms at a local church and thought it would be a great look to put the colored glass in the bottom.  Sort of looking like a pool of water!!  One of the church members came to my studio to see if it was large enough, picked up the bowl, and ran her fingers over the glass and came away with a splinter and a poke.  Horrified, I was.  And that ended the exploration with glass in the bottom of pots.  I still slump bottles for those who ask.  And I have taken glass pieces and slid them inside clear bottles before slumping, but that is the extent of my glass melting.  I agree with Hitch that the combination of glass and ceramic is enticing and I love the aesthetic of the artist that Min posted.   But for me and my studio, we will leave that to the more experienced and educated!!  

Roberta

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I suppose my major objection isn’t to anyone who wants to get technical enough to combine glass and ceramic, and acknowledge the technical difficulties involved. I have a deep and abiding love for those wonderfully crazy people who revel in the science behind the art, and really explore exactly where the possibilities and limits of the materials lie.

My problem is with the folks who know juuust enough to make themselves dangerous and don’t look further, because they know “enough” already. Think the inexperienced teacher that encourages students to melt stained glass into a ceramic cup that’s going into a cone 6 glaze fire because they saw it on Pinterest, and it looked like a doable project for kids. And let’s face it: if the diverse bunch of interests that hangs out here is hard pressed to find good examples of clay and glass being combined safely, and there’s thousands of pins of decor marbles being melted into ring dishes, Pinterest is going to win as the reliable information source. Quantity over quality, unfortunately.  After all, why did this blogger do it in front of The Internet and Everybody if it wasn’t safe? 

Simply melting scrap glass into a clay pot is really, really easy: doing it so that all the safety and technical stuff is observed is a lot less so. 

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7 hours ago, Min said:

@hitchmss, thank you so much for taking the time to elaborate on your process, outcomes and caveats. I was hoping you would chime in here to voice a point of view from the other side of the fence. It's wonderful that we can have a dialogue about this.

The Japanese artist I know about who is melding glass with clay is Misa Tanaka. I don't know what is meant by "melds".

image.png.c65759d0be1684e99d9f0c09b2d61ba4.png   

Nice look, I think I would throw the top vessel and make the glass bottom separate then glue them together with high temperature food grade UV cure epoxy, maybe 5000 psi stuff stronger than the parent materials and rated to 500 degrees or so. especially if liquid does not extend down into the glass area. 

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On 1/12/2019 at 4:38 PM, Min said:

Re the joining of ceramics and glass, if anyone wants a rabbit hole to go down, starting on page 70 of The Combination of Glass and Ceramics as a Means of Artistic Expression by Jessamy Kelly   is a really interesting read albeit a long one.

Very interesting and entertaining! She went down several rabbit holes in her inclusive research and describes reasons and methods well enough to use as jumping off points, as well as good descriptions of "failures." Thanks! Added to my Kindle library.

Edited by Rae Reich

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58 minutes ago, Rae Reich said:

Very interesting and entertaining! She went down several rabbit holes in her inclusive research and describes reasons and methods well enough to use as jumping off points, as well as good descriptions of "failures." Thanks! Added to my Kindle library.

Glad you found it interesting! Yes, there is a labyrinth of rabbit holes isn't there!?!

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