Egyptian Paste (aka Faience)

Experimenting in all facets of Egyptian paste, mixing clay, construction techniques, firing solutions, and finishing ie. cold working is in the scope of our discussion. Perhaps we will have time to get around to some practical uses of Egyptian paste, but mostly research into what works will with this media and what does not.

Sunday, August 08, 2010

Matt and Gloss Surfaces

Matt surface is fully mature and smooth in Egyptian Paste without
any gloss. An increase in alumina makes the surface more refractory creating a matt surface, or so I've read. I suppose conversely, this means that a decrease in alumina would create a gloss surface. Someday I'll monkey around with aluminum hydrate just to prove this to myself. For now, I use different recipes to achieve the gloss or matt.

It may just be the glaze layer is thinner causing the matt surface. It cetainly is not because it is underfired; experiments were run taking the firing a cone or two higher with no discernible different in the matt. This roses has a relatively thick layer that is quite smooth yet still matt. However, it is notice that the shinier Egyptian Paste layer of glaze is much thicker then that of the matt's.

Because I fire on my "bead islands" there does seem to be a gradient from top to bottom of the amount of glaze formed on the bead surface. In the image above, you can see the turquoise bead is nearly white where the glaze formed thinner. Where the glaze formed thicker of the surface is smoother.

The image to the right has two different recipes. The one in the foreground, the turquoise figure and beads is the recipe used in all my post up til now shows a Matt surface. The choir/pale figures in the background is the gloss surface recipe containing more sodium salts. All of my carefully sculpted details are obliterated.

Efflorescence in this gloss recipe was so great it was difficult to load it in the kiln without disturbing the surface. Sticking was another problem; a thick application of kiln wash was always necessary. The cleanup was labor-intensive, especially bead wire. The Matt Paste doesn't stick nearer so much.

On top of this I found I personally prefer the Matt surface , because it looks like Egyptian Paste from antiquity. Plus that, more surface details/textures are discernible with the matt Egyptian Paste; that is important to a sculptor.

The gloss surface has a crackle network that could be a useful design element if considered. Even though I'd abandon the glossy recipe for some time now, I must re-examine gloss recipes. Gloss does seems to be the one that comes up more often in questions/comments.

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