Llewellyn Kouba on fri 16 mar 01
Recently I saw a post that made references to cullet and would like to know
where you can aquire as I would like to try glass in a glaze.
Milton Markey on fri 16 mar 01
Hi Llewellyn and other scrap-glass fans!
Cullet is basically finely-ground scrap glass. The manufacturing process
requires a hammer mill, to get a fine powder.
I make my own coarsely-ground cullet, for some of my glaze work. I prefer
bottle glass, but I've used old hand-ground window glass, and glass from
other sources. Caveat: Avoid automotive window glass. I crush the glass on a
concrete slab, using a hammer. I cover the glass to be crushed with a heavy
canvas cover, to avoid being injured with flying glass chips. Wear eye
protection when doing this, and work gloves. Keep others away from the
crushing site as you swing the hammer! Once the bottle is reduced to
finely-crushed glass, I sweep it with a whisk broom, into a glass container.
I usually strain the crushed glass, to seperate impurities, before mixing it
into a glaze.
When using cullet as a glaze ingredient for a standard recipe, I decrease the
silica and fluxing materials into the batch. This is where you experiment,
making and firing test tiles before coating your wares. Otherwise, the cullet
may create drip patterns, and may flow off the sides of one's wares. When
using cullet in a glaze, always place old pieces of kiln shelf (two coats of
kiln wash), under the cullet-glazed ware. Double-coat all kiln shelves with
"whitewash," as a precautionary measure, too.
Warm, breezy Mojave Desert day. The plant life is slowly waking up, coating
the usually-sandy soil with green desert grasses and purple verbena.