The Illusive Grey Glaze
I had a commission to make a soft grey pot with a “scalloped” rim. I was initially a little daunted by the intricate rim but after drawing multiple templates for the rim I felt I was on top of the task. How difficult can a grey glaze be?
I made two pots. For pot number one, I bought some black stain and mixed it with a white glaze and for pot number two, I mixed back stain in a white underglaze and covered it with a clear glaze. I was, I now realise, foolishly confident, that I would get one if not two nice grey pots.
Ceramic stains are a mixture of oxides that are melted in a kiln and then ground to a fine particle size. Thus I thought they were reasonably stable. The black ceramic stain is usually a saturated loading of one or more oxides, in this case there was, among other things, some copper oxide and some red iron oxide. So when I diluted it to a soft grey looking glaze and underglaze my pots showed copper oxide traits following a reduction firing. Yes definitely not grey. Pot one is showing a copper red and pot two a nice little red copper blush on a soft green.
So after a rethink I decided to try- for pot three – a similar process to pot one, with an oxidation firing cycle ie no reduction and with pot four I bought a commercial grey glaze. Still feeling confident I would succeed. Hah!
There is a saying in ceramics ….”test, test, test!” So I now made new glazes and started testing on small test tiles. I found a lovely soft bluey grey and on testing it seemed perfect. I made pot number five, alas the base cracked and as you can see pot number six is a beauty….just not grey!!!