Monday, 29 December 2014


Let's take a step back from glazes. I need to create several indoor size sculptures and I'm thinking of geodesic dome as a starting point. First I thought of using a wooden mould,and I have to admit that I had lots of fun making it.

 But once made, I was not quite happy with it. I think that the triangles are too small.
So, back to the drawing board and change from 3v dome to 2v dome - it means less triangles for the same circumference.
Also, I have decided to make plaster mould rather than wooden one as it is more rigid.
With this size and shape mould, I will use paper plaster. It has many benefits - I don't need to use cottles, it uses significantly less plaster, which makes it lighter and it is very strong.

Here we go:
left: cardboard model, protected with sticky back plastic
middle & right: applying the "milk coat". Sometimes I make slipcasting moulds the same way so I am in the habit of applying thick "milk coat"

left: smoothing first layer of plaster
middle: finished first layer ("milk coat")
right: mixing second batch of plaster and adding paper pulp ( as soon as plaster has absorbed water)

left: paper plaster can be applied immediately - addition of  
paper makes it stiffer sooner so it holds it's shape
middle: checking that the bottom of the mould is level
right:bottom half of the mould is finished

left: top half is made the same way, except for the opening on the top
right: finished mould and model

Tuesday, 23 December 2014

Test, test and test again                                                                                                             
Sometimes I think painters have it easy. They can mix the colours on a palette, test them on the edge of the paper and immediately know what they look like. I know, I'm (slightly) oversimplifying. For us, testing means starting from the raw ingredients, recipes and good set of scales, sieve and a dust mask. First set of tests are done on small tiles or bits of broken bisque fired shards and selected glazes are then tested on larger surfaces.
This is kind of tertiary testing.... I have sprayed Dry Plum glaze and Copper slip on some triangles and brushed or dipped the Crawl glaze on top. 



Diluted with more water and dipped:

I didn't like the combination of green and dirty pink, so decided to go with pink only. Another test firing.... We are getting closer now.... This one has got only a hint of pink on the ridge ( I have sprayed the Dry Plum glaze, and dipped Crawl):

Here I have brushed the Dry Plum glaze, and dipped Crawl:

And we have a winner.....
Just as well I like it, as I have glazed the full kiln load with the assumption that I would.

On the down side, about half of the bigger triangles in the kiln have cracked in the glaze firing. No idea why...

Tuesday, 16 December 2014

More about glazes                                                                                                             

  I find that clay people are quite polarized on the subject of glazes. Some love the chemistry, science and experimentation of glaze making, and others stay away from it as far as possible. Me, being the curious one, can happily spend weeks mixing and testing glazes just to see what happens,and documented tests are running into several thousands by now.
In my students days I got interested in superimposing glazes ( applying one on top of another). Most literature at the time ( and I'm not sure if that has changed) implied that if you understand the chemical composition of the glaze you can predict the way it looks. Well, that is an extent. There are many more variables, which make it interesting, and ( just the touch) unpredictable... If the chemical composition of the materials was the only relevant data, you would expect that a piece with glaze "A" on top of glaze "B" looks the same as glaze "B" on top of glaze "A". After all, it all melts together. I was quite thrilled to discover that they can look quite distinctly different and thus the testing monster was created.

Couple of years ago I used a bubbly glaze on the "Gateway 21". The effect was created by applying a Crawl glaze on top of the Crater ( or Lava) glaze that I tested years ago:                                                                                                                                                   

I tried to recreate it last year for the "Shape of Thought", but something has changed and the result was quite different. Is the change in supplier of one of the ingredients the culprit? (That is why some of the glaze recipes don't travel well between the continents).
I thought that I should give it another go, with the same disappointing results.

First tile is original Crater glaze with crawl glaze on top. Second tile is Crater glaze with additional 4% of Silicon Carbide, and third tile is new Crater glaze with Crawl glaze on top. Yes, more bubbly, but very different from the original. 

Crater glaze generally contains Silicon Carbide, and crawl glaze "secret ingredient" is light Magnesium Carbonate. I have not come across glaze that combines both materials together, so I thought to give it a go:

Andrea's Fizz glaze:
Magnesium Carbonate light  25%
Nepheline Syenite                 66%
Ball Clay                                  5%
Silicon Carbide                        4%

Result is on top right, with "Fizz" on top of various dry glazes and slips on the other 3 tiles:

Here are the close ups of tests with 2 different Crawl glazes on top of the same dry glazes. I have not tested the Crawl 1 by itself as that is the glaze used on "Shape of Thought". 

I really like the lichen effect of this glaze. One of my favourites!

Wednesday, 10 December 2014

Glaze tests                                                                                                                                                                                                                             
As the number of triangles grows and invades the studio,my mind is turning to glaze choices. I am limited by my description in the brief stating that the sculpture will be white and off white - too late to change my mind now, even if I wanted to.
My plan is to have coloured underglaze and white textural glaze on top.

Here are the first tests before the firing:

and after the firing:

This one looks nice:

I also tested them on the spare triangles:

And I have narrowed them down to these two:

 Which one will be the winner? Wet or dry version of the crawl glaze?? Green or pink background? Or both?

Monday, 1 December 2014

The mould turned out well, and so the making has begun: