|Glaze test tiles|
I love working with clay…it’s such a tactile medium and very therapeutic to sit and hand form or sculpt designs from a little blob of mud. But I have to admit it’s the transformation brought about in the glazing process that I love the most and even when I’m sketching my designs I have in the back of my head the colours and finishes I want to use to bring them to life.
I seem to have accumulated a fair old selection of these magic potions – so much so that when I ordered some new ones last week I had to rearrange my glaze storage drawers to make room.
There are these colourful low fire glazes and under glazes…
More low fire glazes labelled with their colours and firing temperatures for easy selection…
A drawer of Stoneware glazes also labelled….
All glazes are sold off the back of colour swatches and rather like those tester strips you buy when you decorate your home, glazes can turn out very different from what you expected.
|Mayco Stroke and Coat glazes|
Many glazes will give different results depending on the clay body used. The same glaze has been used in both of the images below but the one on the left is a piece made from white earthenware clay and on the right are pieces made from buff earthenware clay. The buff gave a semi matt finish as expected but on the white clay the glaze lost it’s shine and looks more like a stain…not unattractive but differant non-the-less.
|Duncan Courtyard glazes|
When it comes to higher fire glazes the results can be even more unpredictable. Glazes usually stipulate a temperature range within which which they can be fired and where you fire within that range will impact the glaze finish.
This is one of my favourite stoneware glazes and the vases in the image from the manufacturer show the expected results when fired at either end of it’s 1180ºc – 1250ºc firing range. The little fish pendant shows how it turned out when I fired it at 1210ºc (above this the glaze tended to move). It’s pretty close if not identical (of course photographic reproduction and monitors may impact this) and the difference could be down to clay type, type of kiln, reaction to other glazes fired at the same time or any number of factors…I don’t pretend to understand the science behind much of this yet.
|Terracolor stoneware glaze Galaxy|
When I first started with clay I was advised to make up test tiles for glazes so that I had a record of how they came out of my kiln when used with different clays. I did this a few times but as I got more excited about working with glaze it went to the wall a bit and I would just use the components I was making as the tests. This can however be very disappointing when you’ve spent time on a design and the glazed piece doesn’t come out as you expect. Now that I have amassed this collection of glazes I am going back and making test tiles for the clay bodies I use most frequently.
In this next image the glaze on the vases doesn’t seem to change much at either end of the firing range but on my test tile it came out very brown (left quadrant of the tile) when fired in the middle of the range. I don’t know if this is because of the clay I used, the temperature or other factors and I can only find out by further testing. There’s no guarantee though and some of these glazes are sold with the ‘characteristic’ that no two firings will produce identical results!
|Terracolor stoneware glaze Borage Blue|
|Terracolor stoneware glaze South Pacific|
|Mayco, Spectrum and Bath Potters stoneware glazes|