Searching for the Right Glass To Melt!!

[Kate Testa]

Hi there, I'm looking for any information that anyone has on the working properties of the Fenton Heavy Crystal. Does it contain lead? how does it flow. At the studio i work we furnace cast glass tiles into a steel mold. We are currently working with system 96 nuggets but find they too corrosive and not fluid enough to fill out our mold properly. Im looing for any information and help to find the right glass for us. Thanks for any and all help!!!
Kate

[Eben Horton]

that is a lead bearing glass.

Spruce pine batch works well for doing that sort of thing.

[Jordan Kube]

I've heard good things about casting with the spectrum. How hot are you pouring and what does the pattern look like? How thick are your molds and what temperature are they when you pour?

[Wes Hunting]

We have had great results casting spectrum. Both slump casting and pouring.

[Kate Testa]

We have been melting specturm but its just donest flow like we need it to. To make it flow better we have been adding borax to the nuggets which helps but makes the glass much more corrosive and we have already had to change our curcible. The mold that we pour into is an 8x8 steel mold and the tiles that we pour are about an inch thick. The real issue with the glass is that it doenst level out and fill the corners propperly so that we end up with uneven tiles that dont work for our operation.

[Pete VanderLaan]

To say " they don't work for our operation" is kind of ignoring some of the basic properties of glass. If you had a glass that flowed in the watery manner you want it to, it would dissolve your crucible in a very very short time. On this issue, there is simply no free lunch. What makes a glass flow is its relative viscosity when it hits the mold and that very same viscosity at a fixed temperature is the property that makes glass a universal solvent.

Spectrum nuggets are a perfectly reasonable glass. Adding borax to it will genuinely screw it up.

Fenton heavy crystal is comparatively a fairly short glass and is not that nice a glass for a leaded glass. It will emit lead in micrograms when molten.

I would suggest that you need to heat your mold a whole lot more to help make the glass flow. Either that or get the glass a whole lot hotter. Or Both.

[Kate Testa]

We do preheat our mold and pour that glass into it when its around 750-800 degrees. any hotter the glass tends to stick to the mold. I agree that the borax is a bad thing as well, but i guess im just looking for a more casting friendly glass to use. The tiles that we make were made by someone else for the past 10 years and he didnt want to share any of his information with us when we decied to go out on our own, which i understand but it leaves me i the dark about certain things such as what glass would be best for us.

[Wes Hunting]

We use 50/50 plaster silica molds. Bring molds up to 1200 degrees and pour very hot. Average size of molds are 36"w x 36"l x 2"d. Pouring into a steel mold at 750, I doubt that you could get the glass to flow well. I would suggest using a different mold material. Maybe grafite.

[Scott Novota]

ouch they guy would not share....it boggles the mind.


Scott.
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[Jordan Kube]

How hot is the glass when you pour?

[Kate Testa]

We pour it hot at around 2400. We have also tried graphite but it just doesnt hold up long enough.

[Ben Solwitz]

Plaster/silica is probably the way to go as they are inexpensive and easy to make a lot of if you have a rubber positive, so you don't have to worry about them breaking down. You could also try coating your steel mold with graphite, kiln wash, or carbon from a torch, and heating the mold more, but I don't think any of those would stick to the steel that well.

[Pete VanderLaan]

ouch they guy would not share....it boggles the mind.


Scott.
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**********
Hmm I read that thread as "The guy didn't want to share with us when we decided to go out on our own". That sounds like there is more to it than meets the eye.

I don't really explain how to make my work to people either if they have announced their intention to compete with me.

Beyond that. Wes is right- hotter better molds and get the glass hotter. 750F is not a hot mold.

[Scott Novota]

That is also how I read it. I was being a bit snide as I have had someone mad at me for not showing them how to reproduce something down to the color I order for it.

I guess it could have been taken either way. Anyway, I don't know the history so I was just kind of poking them in the ribs a bit about it.

Cheers, I hope it all works out.


Scott.
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[Tom Fuhrman]

Maybe it needs to be a press operation to get all the glass to flow where you need it. The design of the mold can also be critical to the success of production. Not all molds work very well. Designing molds that lend themselves to easy production is an art form all it's own. Working the mold long enough to learn the details of getting it to produce can sometimes take a looooong time.

[Kate Testa]

I don't want people thinking that we are trying to steal any buisness from this guy.. he was using our mold to make our tiles... I respect that he has his own buisness and doesn't want to share certain information, but what he does for his buisness and what we do for our are two completly seperate things, there is no compitition. I'm just looking for any info on what a good glass for us would be OTHER than Spectrum. Or any info abot the FHC. Thanks

[Scott Novota]

Cool. Sorry it is a very interesting debate to be had around the road that we started to hoe.


I am sorry that I kind of leaned toward the shady side when reading your post.

I do hope that the board can help in moving you toward a solution to your problem. The first thing that jumped into my mind was to flip the mold over and let the glasses weight flatten it out on the pour side upside down.


Scott.
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[Pete VanderLaan]

I think Tom has the simplest answer if having a press mark on the piece is not an issue. If the mold is already sticking, heat will just cause more issues, assuming that a mold release is not being used already.

[Peter Bowles]

When you say tiles -just how thick are these castings?

It might be more to do with how you pour the glass into the mold than the viscosity or the physical properties of the glass. If the glass is going to be less than 20mm thick its pretty unrealistic to expect the glass to flow far from the point it leaves the ladle - the temperature of the mould wont have a great deal to do with it if they are fairly thin castings.

[Sandy Dukeshire]

i made a series of cast tiles for a project 12"x12"x1". we would pour, torch then press. pressing sounds easy, but doing it by hand is hard because of trying to keep the press level. many ended up with a thin/thick side. if your project is something you plan on making thousands of i would find a way have the press mounted so you could pull down on a handle or at least add arms to the press to act as a stop. the mold was a graphite base with angle iron sides clamped together and set on top.

[Jay Holden]

i made a series of cast tiles for a project 12"x12"x1". we would pour, torch then press. pressing sounds easy, but doing it by hand is hard because of trying to keep the press level. many ended up with a thin/thick side. if your project is something you plan on making thousands of i would find a way have the press mounted so you could pull down on a handle or at least add arms to the press to act as a stop. the mold was a graphite base with angle iron sides clamped together and set on top.

Tom and Sandy are dead on. Any good Millwright/metal shop should be able to make a simple press for your operation. Pressing is the key to getting the corners to fill out. Should be no problem as long and the press is level.
Jay.

[Kate Testa]

Thanks for all the help!