If you have any experience with glass and clay you might be wondering what's the big deal? Some have used glass to decorate pottery for ages. Well, this is a totally different way of using glass.
One of the presenters at NCECA 2009 was Dr. Robert Kirby who shared his research on using up to and over 60% recycled glass with clay to form the actual clay body, not just decorate it.
Why mix so much recycled glass into the clay? One reason is that it significantly lowers the firing and maturation temperature of ceramics, which will reduce fuel consumption. The pieces get fired at a low temperature yet have the strength of higher fired clay. Using recycled glass in tiles, bricks and sculptures could be a good solution to the problem of what to do with all the glass communities gather.
The glass cannot be home made. You just cannot crush glass yourself and have smooth edges so as not to rip your hands as you work. The product I used was made by a special crushing process that leaves the edges very smooth. It is so soft, some of the finer grades can be used as sandbox sand. It does have the added advantage of being silica free.
If you go to my Blog on the left you will see details of my earlier experiments using recycled glass and clay mixtures for outdoor sculptures.
I did not try different percentages of glass at that time.
The clay I used was White Earthenware from Highwater Clays in Asheville, NC.
In my most recent experiments, I tried to mix as much glass into the clay as I could. These high percentage mixtures definitely need to rest a day or two before you can use them with ease.
I made one tile and one bowl from the resulting mixes.
The tiles were divided into six sections to show plain clay, velvet underglaze, LUG underglaze, majolica, iron oxide and Cone 06 black glaze. The bowls were divided into plain, clear glaze, white glaze and black glaze.
BATCH A : PLAIN CLAY, NOTHING ADDED
BATCH B : WHITE EARTHENWARE WITH 20% PAPER PULP
** Note ... this is the first time I have had this clay body crack.
BATCH C : 50% GLASS & 50% WHITE EARTHENWARE
BATCH D : 60% GLASS & 40% WHITE EARTHENWARE
BATCH K : 50% GLASS & 50% W.E. WITH 20% PAPER PULP
BATCH M : 62% GLASS & 38% WHITE EARTHENWARE
The mix of glass was the highest percentage of clear glass I could get. I could have used a brown mix or a green mix. The white still has a bit of both colors in it as you can see.
None of the pieces made with glass cracked, warped or even shrank much. They only got fired to about Cone 06.
I have placed all of these pieces outdoors to see what the cold winter temperatures ( bear in mind, this is North Carolina not Maine! ) and rainfall will do to them.
I don't have an opinion yet on the whole process. It is too early in the 'life' of this glass to have a steady supply for experiments. Once large industries start using it perhaps supplies will be more readily available to small businesses. It can also be used as mulch in landscaping so maybe one day we will be able to grab it at the neighborhood Ace Hardware Store.
I will be bringing these pieces along with one of the garden villas to NCECA 2009 in Philadelphia so those who visit the clayart room get to handle them.