Friday, September 6, 2013

test tumblers

A look at the tumblers I used to test different glazes to see how they'd look with the transfer paper decals:
 Not all the glazes are different.  I wanted to see how a couple of pale blue slips looked under glossy and satin white glazes so I have some doubles on those I tested with slip and without.  They all seemed to turn out fine.  There may be one gray-green glaze that is borderline too dark.  I've been thinking of reducing the amount of colorant in that glaze anyway. I took several of these down to Riverside Artists Gallery today and plan to have a few at the farmer's market tomorrow.  Yes, I'm finally getting back to River City Farmer's Market. I haven't decided on how often I'll be there, but plan to eventually have a schedule of once or twice a month so people will know when they can find me.
 Randy's Red is inside the light gray tumbler on the left.  Great color, but bubbled a little in one place after the third firing.  Not blistered, more like a cluster of solid, tiny pimples. Lovely description.

This may be my favorite glaze with the decals.  I'm not sure what I will use on mugs, though. I'll have more surface to work with when I make mugs, so glaze choice will be linked to adding decorative touches with slips, engobes, and/or overglaze.

This is one tumbler I didn't fire with a decal because of glaze crazing:
The crazing developed sometime within 24 hours after removing the tumbler from the glaze firing.  Confused?  The decals require an extra firing.  Here's the routine:
 (1) bisque fire- A partial firing that can be done once the pots (greenware) are dry.  After this firing the clay is still porous so glaze adheres, but strong enough that it holds up to the glazing process.
(2) glaze firing- This time the kiln is firing to a higher temperature that melts the glaze and vitrifies the clay so it is no longer porous. 
(3) bisque fire again.  Pots with decals go in another bisque firing to melt the iron oxide in the decal into the glaze. The temperature the decals need to fuse with glaze coincides with the regular bisque temperature.

I googled glossy clear glaze crazing and hope I found the solution.  Click on the link if you've had the same problem. Apparently it's all in the soaking time.  I always thought the soak took place once you got to cone 6, which made it difficult to hold because pretty soon cone seven would be going over.  In answering someone else's question about crazing with this glaze Ron Roy explains cone 6 should be at about the 2:00 position when the soak starts. Oh.
If you are from this area then you get why I chose the sternwheel image for the decals. The Sternwheel Festival is underway.  I took a couple of pictures this morning of the boats lined up at the levee.

One last picture.  Once in awhile I see an unusual golden light coming in the basement windows while I'm working in the evenings. The other night I stopped what I was doing to come up and see the sky. 

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