In today’s post, Martha Grover explains that her surfaces, which are often mistaken for soda-fired surfaces, are actually achieved through spraying on various cone 10 glazes. – Jennifer Harnetty, editor.
I started spraying my glazes about 4 years ago. I found that I was unable to achieve evenly layered surfaces and color transitions through traditional methods of dipping and pouring. By using two sprayers, one small for my bright colors concentrated at the edges, and a large one for the overall piece, I am able to create a varied, even surface that shifts from a bright color to light seamlessly.
To begin, I bisque my porcelain to cone 04. I find any lower makes my work far too fragile, while firing it hotter causes the piece not to take glaze well. Each piece is then waxed on the bottom and any other surface I wish to remain glaze free – in the case of the butter dish, I also wax the top slab of the lid.
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I then pour glaze into the inside of each piece. I have tried spraying all layers on the interior, and find that is extremely difficult to fully cover any interior vertical surface, especially in bulbous forms. By pouring this first layer, usually with my Salt Yellow Base, I ensure that the interior will be completely glazed. Then I wipe off any excess that may have spilled over the edge.
Next I let the work sit and dry overnight – this is VERY important. If I try to glaze the exterior on the same day, the glaze will pull away from the surface due to over saturation and I end up with unglazed bubbles on the finished work. The next day, I apply my brown dots with a fine tipped slip trailer. These are a high iron engobes, which can be put on either bisque or green ware.
Always spray in a well ventilated area or spray booth.
Be sure to wear a respirator.
I always wear latex gloves and ear protection as well.
The next step is to dip any handles. Much like the interior of the pots, it is hard to get a full coating of glaze on the backside of a handle with the sprayer.
I then proceed to spray the whole piece using my large sprayer, a “Husky” siphon feed spray purchased at Home Depot. I first spray on my clear layer. I make sure to spray up under any folded edges. I make this layer thicker at the top edge and fade out as I get to the foot of the pot. Once again, I wipe off any overspray that may cause dripping in the next layer.
I change over now to my opaque glaze. For this, I use my Salt Yellow Base, with whichever colorant I need to achieve the desired color; on this butter dish it is just the base alone. This layer I spray heavier at the bottom and lighter at the top edge. This varied layering is what causes the snowy affect in the glaze where the two cross over one another.
The final step is to once again wipe off any over spray. In places where it is difficult to clean with a sponge, I use a metal tool to scrape off excess glaze and then a damp sponge to clean off any remaining residue.
The finished piece is fired then to cone 11 oxidation in an electric kiln. I always sand the exposed porcelain after the final firing to create a smooth silky surface.
|Green or Bisque Slip
Cone 10 Engobe
|For Brown Add:|
|Red Iron Oxide||10%|
|Black Iron Oxide||5%|
|Gawk’s Clear||Cone 10 Glaze||Salt Yellow Base||Cone 10 Glaze|
|Barium Carbonate||11||Ball Clay||5|
|Yellow:||Red Iron Oxide||1%|
To learn more about Martha Grover or see more images of her work, please visit http://www.marthahgrover.com/