Technical Project

18902399_1576683595678128_1321901545_nHaving this technical project running alongside our module has been essential for my material understanding and further explore my glaze alchemy knowledge. Coming back from South Korea I was very much inspired by the Celadon glazes which are very much embed within their ceramic culture.  I was interested in experimenting with Copper glazes and exploring different firing atmospheres both oxidation and reduction to achieve two different glaze finishes although using the same recipe. An intriguing metaphor in the exploration of cultural differences yet its similarities, a theme that was very much so at the core of my field module.

I began by looking at “The Handbook of Glaze Recipes” by Linda Bloomfield and picking out two recipes, one of which was a ‘David Leach’ porcelain base glaze and I decided to add some additions.

(1) Derek Emms Red:

  • Soda Feldspar                               42
  • Flint                                                19
  • Whiting                                          14
  • High Alkaline Frit                        14
  • China Clay                                      5
  • Tin Oxide                                        5
  • Copper Carbonate                         1

(2) ‘David Leach’ porcelain base glaze with addition of 2% Copper Carbonate:

  • China Clay                                      25
  • Feldspar                                          25
  • Flint                                                 25
  • Whiting                                           25
  • Copper Carbonate                         2

(3) ‘David Leach’ porcelain base glaze with addition of 2% Copper Carbonate and 5% Tin Oxide:

  • China Clay                                      25
  • Feldspar                                          25
  • Flint                                                 25
  • Whiting                                           25
  • Copper Carbonate                         2
  • Tin Oxide                                        5


Oxidation tests came out good with smother green on test (3) with the addition of Tin Oxide in comparison with test (2). Reduction test came out under fired although some glossy red starts to show up on test (1).IMG_9948

With another reduction firing the tests didn’t fire to the firing range they were suppose to (1260°-1300°C). The gas kiln had a few problems at the time and wasn’t being very reliable, so I began to think if I could possibly create a reduction atmosphere within an oxidation firing.

I built a saggar which contained the test glazes and contained some sort of combustible which in theory (or at least in my head) would create a reduction atmosphere. The deprivation of oxygen within the saggar was attempted by surrounding the container with silica sand. Of course the reduction didn’t really happen, although, some ash of the newspaper mixed with test (2) which created the effect that you can see bellow.IMG_9946

Wanting to use my glazes inside my coiled porcelain vessels, I quickly realised I was going on the wrong path as in colour palette wise due to the darkness of the glazes overpowering the interior of the forms. In addition, a couple of students were also looking at copper glazes and with high demands for the gas kiln and it not being reliable, I though I should move on with a glaze that would suit my vessels.

(1)Brushed/Thin layer (2)Brushed/Thick Layer (3)Poured/Thin layer (4)Poured/Thick Layer

A lovely subtle white with a halo of pink when really thick. Also learned to clean my brushes before using them as they often have oxides or other materials. The glaze fits the porcelain body perfectly at 1280°C.IMG_9961With some research I found out that a tin glaze with a small addition of chrome oxide will go pink but with higher percentages it will dramatically go green. Not having very precise scales I roughly measured 3 measurements of Chrome Oxide into my Tin glaze.


(1)Original Tin glaze (2)Addition of Chrome Oxide bellow 1%  (3)Addition of Chrome Oxide around 1% (4)Addition of Chrome Oxide around 5%

These results got me really excited and felt I was achieving something, therefore I decide to invest on some scales that measures to 0.01g up to 500g to get more precise results. Observing my results I know that test (3) will be achieved with additions of Chrome Oxide in between 0% and 1%.IMG_9982IMG_9980Done the silly mistake by not sieving my glazes which got me slightly worried about my first results, however when I sieved the glazes the colour came out uniformly.

With further glaze testing I concluded that the pink will be achieved with addition of Chrome Oxide into the Tin glaze in between 0% and 0.2% which is a very small margin. However, mathematically between 0 and 0.2 there are an infinite amount of numbers, so technically I should be able to test it, perhaps by increasing the amount of the base glaze instead of measuring 100g of glaze.

(1) Chrome oxide over Tin glaze (2) Chrome oxide under Tin glaze

I began to think of the possibility of watering down chrome oxide and then either layering the oxide under or over the glaze. Above, I added a layer of chrome mixed with water at the time increasing it by one all around the cups. As you can see I managed to achieve some great pinks the one under the glaze being more subtle and the one above the glaze stronger.

A= 0.5g of Chrome Oxide mixed into 50ml of water
B= 1g of Chrome Oxide mixed into 50ml of water
C= 2g of Chrome Oxide mixed into 50ml of water
Numbers under Letter= Number of layers of watered down mixture

I then decided to make three tests ranging from 0.05g, 0.1g and 0.2g of Chrome Oxide, however, we didn’t have any Quartz therefore I added the same amount of Flint which is a silica substitute. Unfortunately, the results didn’t come out as I expected so I decided to get more Quartz to continue my investigation.IMG_9968Managging to get the Quartz was great as I explored little addition of 0.05g, 0.1g and 0.15g of Chrome into my original tin glaze resulting the tests bellow.IMG_0013Been exploring different firing temperature as to what the expected 1280°C is due to the nature of my vessels being made out of porcelain which tend to warp at higher temperatures, therefore on the results bellow I went slightly lower, to 1260°C. The glaze doesn’t seem to bad in contrast with the 1280°C firing, however, the quality of the fired porcelain seems slightly better in my opinion.

I fired three porcelain vessels to three temperatures, 1240°C, 1260°C and 1280°C I began to notice some differences. when I took the porcelain to 1280°C it has really vitrified  which have a slightly grayer tone as when as it felt more dense, at 1260°C there aren’t much differences but when we move to 1240°C the porcelain is much lighter and I feel it has a different tactile quality which I like, in addition at that temperature it tends to warp less in comparison with higher temperatures. Although the differences are not very visible on the picture bellow, they are there.

IMG_9991I found having this project alongside our module was essential for us to have a better understanding of materials and glazes.  Knowing what you want and being selective of what you want to achieve is the essence of this exploration. Really interested in observing the glaze qualities of small additions of material into a glaze and how that affects it. There is so much about ceramics and that’s probably why I persue it and loving it.