Blue Links

1/2' x 1/2' 5"

Clay cast glass with clay left on the surface.

 

 

How Blue Links were made

First I made them in wax.

I did that by dipping a solid glass piece with the same shape in to melted wax. I had made it in the hotshop earlier.(I had put vaseline on the glass so the wax would not stick to the glass. I could also have formed something in clay and smeard some vaseline on it and dipped that. When the wax is hard you open it up where it will be the easiest to get out the piece inside. In my case it was on the side. This method of mine is a great way to skip the plaster mold stage if you don't have to have any repeated detail in your wax piece. You can always make your marks into the wax afterwards like I did in this case.
( see picture above.)

Here are two forms that show how the mold looked like for the glass in Blue Links.

The only difference is that these were cast separately.

The technique I used is based on bronze casting techniques that are thought to originate from ancient Africa and Asia. My version of the method is as follows:

• First the piece is formed in wax. ( I used a standard brown wax. But best is to use beeswax for it has lower melting point)
• Then a protective layer is smeared onto the wax. This layer will not crack when it dries. People in Gana still use this method to cast bronze statuettes. (Charcoal with slip in it and then they use cowdroppings, clay and palmfiber to create a mold )
• I used very corse clay to cover over the charcoal layer and then regular clay over that and to create the sprue cup.( the Gana people do it this part a little different and I will not go into that here)
• NiCr wire was wrapped around the form, to keep it together during the firing.( something I desided to do to make sure the glass didn't go every where)
• The piece was fired upside down at a low temperature in a gas kiln to extract the wax.
• Kiln cement was put in all the cracks that had formed in the clay.( they do that differently)
• Put recycled Gabberts glass (broken up clear glass (cullet( floor and glass tool schraps) from a blowing factury) into the mold along with copper scale to create a green color.
• Fired slowly (17 hours or so) in an electric kiln to1600F and hold there for about 2-3 hours to make sure all the glass had moved into the mold from the cup part. Then the kiln temperature is taken down to annealing temperature of Gabbert glass (950F) and and left there for about 12 hours so the glass can get a chance to get some of it's stress out (Try to make it rather fast. Specially beween 1200F-1100F so you don't get divitrified glass ( The glass crystalizes - the glass becomes mat or spotty). Then the temperature is slowly taken down (10 hours or so) to the strain point (200F lower) of the glass. That is the last chance for the glass to get all the stress out. Soak it there for about 8 hours and then go in about 6 hours down to room temperature. Each firing is different depending on the thickness of the glass being cast. I like to be on the safe site and most often over anneal my work. The oven can not be opened up after the temperature has gone down to the annealing temperature for you will be risking that your piece will break from a thermal shock of the sudden change in temperature you create by opening up the door. It is a good rule to let the piece sit in the kiln for a day or so after it has reached the room temperature before you decide to take it out of its mold. Don't run cold water on the glass to clean it. Try to make it as close to room temperature if you need water.

Blue Links during the wax burnout step.

To get the Blue Links out of the mold I used a hammer and an old sharpened skrewdriver.  

I was not fully comfortable with this method and decided to find a different way to create a closed off mold. My main problem was the cracking of the clay because I had used a wax type that was hard and the clay I used contracted so much around it so there where lots of cracks that showed up on the final pieces. So what I do now is to put paper mache around a form that I like and take that off like it was wax, talked about above and glue it back together and smear my clay over it. The moisture from the clay will soften up the paper and make it give as the clay dries without changing the form or cracks forming on the clay. You can see how I work with that method on this page. This way I don't have to deal with wax burnout and I'm recycling my junk mail.