Post 11 Glaze layering

Of all the glazes I trialled recently there were only a very few that were compelling and I mean irresistibly compelling. That’s got to be the criteria, not just ok. I have to admit though, the longer I look at some of them the better they look. Its a bit like looking at a paint swatch and wondering what it would look like in the wall. I did get a couple of clear glazes that worked out very well and if ever I need one, I now have a good choice.

Layering of glazes gives interesting results and adds an additional spontaneous flavour to the outcome. It also offers an alternative to a homogeneous surface finish and colour from a single glaze finish. Testing a number of combinations will definitely be a priority for the next tests. Amaco offer a great range of commercial glazes and have a full pictorial offering to demonstrate the results that can be achieved with glaze layering. http://www.amaco.com/amaco-school/layering-amaco-glazes/  The results have as much if not more to do with chemistry as colour.

And so it can only be back to the drawing board. I’ve looked at the recipes and where they were too glossy, or too transparent or lacked colour, made adjustments for another trial set. All it takes is a few hours and kilos of clay to produce another few dozen test tiles. That’s the easy part, before the weighing out of the multiple ingredients for each test glaze.

While getting ready for this I’ve produced another couple of pots too and so now have the kiln set for a bisque firing with three pots and test tiles to go. 

Here is a picture of a visitor to my garden this morning.

Post 10 Glaze trial results

This trial firing very much confirmed my expectations that in testing glaze formulae it is much more about the local source of the ingredients and the firing of the kiln itself, than the recipe, which deternmins the outcome. Many many of the tests produced results that were quite unexpected. Surface finish of glazes that were suggested to be satin or matte ended up high gloss and in very few cases were the colours as expected. Certainly where ingredients have different chemical compositions the colourants will behave differently.
I do now have a few formulations however that I will use on the next set of pots. The following picture show a set of the more prospective;

One of the goals I had in going into this set of trials was to find glazes that simulated antique bronze or cast/wrought iron colouration and surface finish. I now have a few recipes that fit the bill. In preparing for the firing I made up a few small figures from medieval or ancient history to give the glaze some context.

This is the first in the shape of a lion. Nice glaze with metalic look and feel and a certain suggestion of tarnish.

And the second is a copy of a Roman sheep figure in a slightly glossier glaze although the test tile itself is a little more satin.

 

A copy of an Egyptian sphinx with a greenish tinted glaze.

 

And finally another Egyptian figure - of a sheep.

There's no doubt that even in application the glazes look different for the test tiles.

The following are a number of the prospects I'll now be working on for final pot glazing.

 This rather exhausting testing does raise almost more questions than it answers. With the formulation variability of raw ingredients the focus has to be on the target surface finish as a first priority and then the colourants second. All that means is that this testing process is just beginning. This has just been stage one of an unknown number in the series!

Post 9 The big oval pot

In Post 7 I covered the making of a new mould - which is quite a deep oval. It took a couple of weeks for the mould to finally dry and now I've pulled the first stoneware pot. The clay has a little iron in it so at this stage has a pink tone but will finally fire to a buff brown. You can see the colour in the pots of Post 5.
In this picture it is very close to bone dry and has already shrunk about 4%.  For those into the detail, at this point it is about 455 x 340 x 108. I think it will finish up after the final firing at about 420x320x100. 

In the conditions that prevail here I like to have a little more than the minimum potting medium for my trees to help them retain some moisture through the summer days, so am quite happy to have the deeper pot. Using the same mould I'll also be able to turn out more shallow pots as well as be able to apply surface profiling after they are pulled.

This is pot number 14. With an oval pot the drying stresses are better spread giving better stability or at least less noticeable distortion. Now I need to get on and make another 3 or 4 to fill the kiln for a bisque fire.

With this post the history has been covered and the blog is up to date. Tomorrow I'm going to have a glaze run to fire those test tiles from Post 8.