Mark Mondloch on tue 19 feb 02
Thanks Ruth, that was very interesting.
I've been playing around with making an ash glaze from my scrap glaze since
I sponge off quite a bit of glaze with the glazing methods I use and
generate allot of scrap- and can't throw anything away you know. ;) I've
been using 1 part ash, 1 part scrap glaze (I just think of the glaze scrap
as feldspar since most of my other glazes are primarily spar),and 1 part
redart clay. Interesting matt, surprisingly close to your #16 and #21 tiles.
If I add 10% silica it gets smooth and glassy which also seems to match your
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake ,Wi 53075
----- Original Message -----
From: "Ruth Ballou"
Sent: Tuesday, February 19, 2002 9:19 AM
Subject: Re: Flashing and cooling in wood-fired kilns
> Ash effect lovers,
> I've posted 3 scans of ash tests done on a biaxial grid at
> he lower right hand corner is a bit blown out, but I think the rest of the
> tile comes through okay. These tests show the result of varying alumina
> silica on a grid of 35 glazes with a set group of flux materials. More
> information on this method is available at < http://ian.currie.to/ >. I
> use a 60/40 ratio of ash/spar for the flux corner (lower left corner).
> content increases to 50% as you move up the tile;silica increases to 60%
> you move to the right. I picked the 60/40 ratio based on a line blend of
> ash/spar. Interestingly, this happens to be the same ratio of calcium/spar
> for the .9 CaO grid from Ian's first book, Stoneware Glazes. Since a lot
> ash is predominately CaO, I don't think this is an accident that I that I
> chose this ratio. I've learned that some of the Chinese lime historic
> glazes have been analyzed to have .9 CaO (according to Nigel Wood's book).
> I imagine that potters working with available materials have repeated
> experiments many times. For comparison, the single tiles are glaze 16 and
> 21 from the .9CaO set.
> All these recent posts about ash on pots sent me to look at my grid tiles
> again and compare them to a pot with a heavy hit of ash that was fired in
> train kiln.There on the pot are a range of the same glazes that appear in
> the high clay area of both grids (ash/spar and .9 CaO) These glazes are
> in silica and have moderate amount of alumina. Makes sense as the
> underlying clay body is contributing to the glaze.
> Guess I'll go look at my tiles some more and see what else I see and think
> about them some more.
> Ruth Ballou
> Silver Spring, MD
> Didn't get to sit down much during the firing. Forgot my chair. Stood next
> to the warm kiln instead. Unload tomorrow.