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.

Wednesday, August 18, 2010

Twice-cooked travellers

Thanks Anitra, for the invitation to contribute. I have already learned a lot from you, and now Kriket as well - thanks to you both. My background is in glass and I am a newcomer to faience, so don't expect any expert advice here, probably more in the way of problems and questions...

Unfortunately I've had to be away from home a lot lately which has been frustrating... However, on the latest trip I decided to take it all with me. The first photo shows my tiny portable kiln and raw materials ready for the road.

I hadn't used this kiln before for temperatures higher than 540C (annealing glass beads) and I forgot to take with me the instructions for the controller. Searching online for those instructions led to an important discovery - that the top temp for this kiln is actually 920C not 1050C as I had thought... Would that be high enough for the paste? I had a go anyway and the results seemed OK, using Anitra's recipe of 16:4:2 (+ Cu Carbonate), firing the kiln at maximum for nearly an hour - but no pyrometer so not sure exactly what actual temperature. Just to see what would happen, on my return home I re-fired the pieces together with a new batch in my larger kiln, to 1000C. They don't appear any different after the 2nd firing... but at least don't seem to have suffered at all. Now I think I might try fusing two or more fired pieces - or adding detail with fresh paste to fired pieces to see if it's possible to build up more complex pieces in stages. Has anyone else tried doing this? I imagine the new bits will simply shrink and crack away from the old...

The second picture shows some of the twice-cooked pieces.

Now a very basic question for those who have more experience of this material. The mushroom-shaped lump, top left, has thicker glaze on the right-hand side and it has also bubbled - looks quite nice, actually, though doesn't show up very well in the pic. Before firing it had a lot more of the salty efflorescence on that side than the other, possibly due to the sun shining on it as it dried. Anitra has mentioned size and position in kiln as factors affecting glaze thickness, but would I be right in assuming that uneven drying could lead to uneven wicking of the salts in the mix and thus to uneven glazing? Has anyone found out how to avoid this, or perhaps how to exploit it in interesting ways?

Coming up... I'm wondering about making and using moulds (or is that "molds" with you?) for faience. Anyone out there with ideas or experience? I'm already messing around with the basic paste ingredients and an unusual glass-moulding technique, hoping to report back soon...

Tuesday, August 17, 2010

Some results

Above are the results of the firing (following on from my last post). I was predominantly making a batch of dark blue beads as I knew they would not be affected by 'the flash'. In this firing I did a couple of test wires to see if I could subdue 'the flash' on the lighter copper, turquoise colours.
Following Anitra's advice I painted some of the wires with kiln wash and I left some of the wires bare. I did, however, clean down all the wires first - grinding off any residue from past firings. I also used a variety of gauges of wire from .7mm to 2mm. After painting the wires I left them to dry thoroughly and actually left the beads to dry out a little as well before carefully threading them onto the coated wires. They went on smoothly enough with little disruption to the kiln wash on the painted wires. There seemed to be no indication of the 'the flash' during making or during drying - even on the wires that were uncoated.
BUT when I opened the kiln today there it was! It had appeared on the gaps of the wires between the beads - on both the wires painted with the kiln wash and the plain wires. I was hoping it would have been contained to these areas but on closer inspection I can see it still migrated to the surface of some of the beads.
So I am due to make a large batch of pale colours and of course am concerned as to how to beat this. Anitra, you suggested coating the wires in a wax of some sort? Do you mind explaining that process please? My mind is telling me that the wax will just melt....... Also I have read that another ceramist having this problem coated her wires with enamel but again I have no idea what that would entail.
Is there another kind of wire that could be used in place of a nickel based wire? Perhaps stainless steel - is it ok to fire this in an electric kiln? I wonder if  it is possible to source thin 'ceramic' wires of some description as it seems to me that it is the metal that is the key to encouraging the growth of 'the flash'.

Thursday, August 12, 2010

function over beauty

4 section bead rack to hold wires of different lengths
and to maximise kiln space
standard 3 tiered rack - holds about 20 wires
beads drying a little before threading them onto 
their wires
Several people have contacted me in the last week or so asking about how I support my beads whilst they are drying and then during the firing process.  I have custom made bead racks out of earthenware clay to suit both the size of my kiln and the size of the beads I want to fire. Larger beads need more support so need to be on shorter nichrome wires supported at intervals of about 10cm or less. Tiny beads not weighing much can be threaded onto longer 20 - 25cm wires. The racks are not elegant like the ones you would purchase from a ceramic supplies but they are way cheaper and do the job just as well. The beads sit on their wires for about 3-4 days before being fired to around 1040 degrees C. Then with a bit of luck they come out of the kiln transformed from white, dry, unexciting beads to shiny, glossy, gorgeous ones, ready to be designed into jewellery

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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Tuesday, August 03, 2010

A curious effect

Hi Anitra,
I have a noticed in my last 2 firings that quite a few of the beads have an unusual, yellow, fluorescent sheen to parts of their surfaces. It seems to be appearing on the paler colours - either the plain beads (with no colouring oxide in them) the pale turquoise beads and some of the beads with rutile as a colouring oxide.
It is quite unsightly and I am at a loss as to what is causing it and how to rectify it. I remember this happening on a random basis years ago.
I do not think it is being caused by the salt in the water as it has not occurred during all recent firings with salt present.
It only appears on some beads on each of the wires - others on the same wires are yellow free.
I feel it could have something to do with a reaction with the nichrome wire somehow and it is flashing onto the beads. It seems to be most obvious on the tops of the beads and at the holes.
I have bought brand new wire and threaded almost dry beads onto clean wires to test if it was happening during drying and it still occurred.
I have noticed it appear at times while making the beads - so it is present before firings. It seems to appear it of no-where.
If I look closely at the gaps in the wire between beads pre and post firing I think I can detect a small amount of greenish/yellowing on the wire.
Hmmm very curious and if anyone has any thoughts I love some help please.