Saturday, June 2, 2012

getting the matte back

This bowl is from my student days (Thiel College, Greenville, PA). The glaze is called Wonderful White and is cone 10 reduction. If applied more thickly it really would be white, however I preferred the stony gray color I got from a thinner application.

I have been trying to immitate that glaze in cone 6 oxidation. The tile at left was pretty good, although I made that test glaze a little too thin. Thing is, that was in my old Paragon kiln which took a long time to cool down from cone 6- about 48 hours. In my relatively new Skutt kiln, which cools much faster, the matte turned into a glossy glaze.  It wasn't until recently that I learned the faster rate of cooling can change a glaze from matte to glossy.  The tile at right is the same glaze.  I left out colorants (some gray stain and a pinch of cobalt ox.) in case they were lowering the melting point and I slowed the cool-down phase to 150 degrees F. per hour.  Still turned out glossy.  

The planter  at left was fired with a controlled cool-down of 100 degrees F. per hour and is much less glossy than the bud vase next to it which was in the 150 degree cool-down schedule.  This is what I'm after, but what the glaze should turn out like is often a matter of perception and individual taste.  As Wonderful White was more attractive to me when it was gray, I have sold many of these bud vases in the glossier rendition of that matte glaze and have orders for more.

In case the gray matte didn't work out, I also tested some variations of this Robin's Egg Blue glaze which has always been reliably matte.  Yes, I'm talking about the glaze on the finial, which is not robin's egg blue, I know.  But when it's put on a lighter clay... 

Same glaze on the finial is on this lighter clay test tile in front. Like that very much!  The others are, left to right, the base for Robin's Egg Blue, no colorant, base with 4 percent gray stain, and 4 percent gray stain with 2 percent rutile.  The gray alone was not  interesting at all, but with the rutile added it started taking on some character.  Might be worth further experimenting.

Ginkgo leaf planters got fired Thursday and these two sold today. A note about the weathered bronze-green at right:  I thought I could brush this glaze but it wasn't brushable so I dipped.  Since I already glazed the inside with gunmetal, I plugged up the drainage hole with a balled up piece of paper towel, then coated the paper towel, inside and out, with wax resist.  Also put about 1/2 inch band of wax resist around the ginkgo leaf collar, waited for all to dry, then dipped in the glaze.  In the past I've used putty, or whatever that stuff is for hanging posters, to plug up the drain hole.  I did read up on how to modify glaze to make it brush better and may try that another time.  I was a little nervous about playing around with adding stuff to the glaze since I had a customer waiting.

1 comment:

  1. I use a slow cool down to 1500 then I let it cool naturally to achieve my matts and I have a Skutt. I notice different places in my kiln fire differently even with the same glaze though. The bird finial looks like stone, great color.


Blog Archive