This was a project I did in a group for my Materials Science class. Since I had access to a laboratory full of materials testing equipment, I'll give you some extra scientific data. But if you happen to have access to casting equipment at home, you should be able to produce similar effects!
Necessary materials:
-glass
-something to smash glass
-materials to make an investment mold (wax, investment plaster, flasks, a vacuum sealer)
-something big enough to hold glass over investment at around 850 degrees C
(Please read through the steps first- this materials list is probably not comprehensive.)
I'm not an expert- none of us had tried working with glass before this project. If you have advice, please comment!
Necessary materials:
-glass
-something to smash glass
-materials to make an investment mold (wax, investment plaster, flasks, a vacuum sealer)
-something big enough to hold glass over investment at around 850 degrees C
(Please read through the steps first- this materials list is probably not comprehensive.)
I'm not an expert- none of us had tried working with glass before this project. If you have advice, please comment!
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Signing UpStep 1: Make wax pieces
Make positives of whatever it is you plan to cast. Sculpting, carving, or braiding thin wax pieces is easiest.
Another option is to copy an existing object using silicone molding and a wax injector. I used mold-making rubber, but here is an instructable for a different way to make silicone molds. Make sure there is an opening from the side of your mold to your object so that you can inject wax with the wax injector. I made several wax copies of a phoenix figurine using the silicone mold pictured.
The objects which cast best in glass for us were the solid figurines, such as the animals pictured. However, some of the more delicate objects (some rings, a phoenix) also came out well.
Attach your objects to a wax sprue.
Another option is to copy an existing object using silicone molding and a wax injector. I used mold-making rubber, but here is an instructable for a different way to make silicone molds. Make sure there is an opening from the side of your mold to your object so that you can inject wax with the wax injector. I made several wax copies of a phoenix figurine using the silicone mold pictured.
The objects which cast best in glass for us were the solid figurines, such as the animals pictured. However, some of the more delicate objects (some rings, a phoenix) also came out well.
Attach your objects to a wax sprue.
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The same investment should work; the teacher whose materials I was using had only worked with metal before, and I just used the metal materials for glass.
However, here is another excellent casting instructable: http://www.instructables.com/id/Lost-Wax-Casting/ and the author of that one recommends 'satin cast' by kerr for detailed jewelry casting in the comments.
Don't cool it faster than you have to.
Cooling iron, zinc, steel in cold water will leave microfractures throughout the surface if it doesn't shatter the part outright.
Cooling aluminum, magnesium results in a stupidly soft and unmachinable alloy, regardless of your starting material. 6061 after a water quench ends up with properties like 1001.
Just let your parts air cool. You avoid putting unnecessary molecular and physical stress on them.
I'm sure some of it was absorbed by the glass.
Secondly, what the hell is up with the purple gaffer's glass? Are they nuts?!? Who puts that much lead in something? Obviously, this is not directed at you, selkeymoonbeam, - just whatever criminally insane freak that decided to make that available to the public without a giant - WARNING! THIS GLASS IS INSANELY TOXIC! - label all over it. Lead in glass will leach out in 5% (vinegar-level) solutions of acetic acid - I don't want to think about how much would leach out in stomach acid if someone (i.e. someone under the age of six) swallowed a bead made of that glass. <rant ends>
Thirdly, I wonder if it's the potassium that makes the wine bottles green. European forest glass frequently had a greenish cast to it, and it seems likely that it was because glass makers were using ash/potash for their various alkali carbonates, which would contain (in that region) I high percentage of potassium. That is just very interesting ....
Fourthly, that is just a very cool instrucable.
When glass is re-melted over and over, it tends to develop a greenish tint. This might happen because a piece of metal from the blow pipe was re-melted, or from something in the furnace like the heating elements degrading (my guess).
I wouldn't hesitate to put a piece of yellow glass in my mouth (even though it contains cadmium), but if I'm melting it in the fire, I'll definitely be working under a ventilation system. I don't think using lead crystal glassware on a day to day basis poses any serious health risks, but storing alcohol in it for any long period of time should be avoided.
This instructable is great! I enjoyed the laboratory approach very much.
I think that the general feeling has been that lead crystal is fairly innocuous used as intended - i.e. not for storing food. However, as lead can leach out in measurable amounts if even low concentrations of a weak acid - like vinegar - is stored in it overnight, I think that the conventional view on lead glass is about to be revised. If there are small children in the house, I would strongly advise against using lead crystal at all. I would imagine that the same would hold true for other heavy metals in glass, although I haven't seen any studies on the subject, so this is just a guess.
The extremely high levels of lead in the purple glass used here was dismaying to me because, if it were made into a bead, that seems like the exact sort of thing a child would want to put in his or her mouth. Makers of that kind of glass always seem to have this thought-bubble floating over their heads "this is harmless as long as people use it the way I intend." The reality is that the instant this product leaves their posession, its use will probably bear little resemblance to their initial intention, because people only see that the color is pretty and don't understand how the color is achieved, or the dangers the product can pose.
The purple glass- I'm not sure what percentage normal lead glass has of lead, but leaded glass is still pretty common. Many people have lead glass decanters for alcohol- which is really bad, because it takes about an hour for your decanter to poison your wine. Also, Swarovski makes a lot of little figurines that people give to little girls, and that is high lead content as well. Some online sources said that lead crystal wineglasses could be all right, though, since you drink it more quickly... but yeah. They should really label that stuff more clearly. For this particular glass, I believe it was professional glassblower's glass, and I got it via my professor, so it might not be "publicly" available per se.
I had speculated that potassium was a coloring agent, but found no evidence to support it. Another interesting note on the wine bottle glass, though: since it was for storing wine, it's opaque to UV light!