Colour Line Blends
Aim:
1. To introduce you to the testing method known as Line Blending.
2. To use line blends as a tool for discovering glaze colour.
3. To examine the following glaze's colour response to Iron Oxide, Copper Carbonate, Manganese Dioxide, Titanium Dioxide, Nickle Oxide, Chrome Oxide and Cobalt Carbonate.
|
Potash Feldspar |
80g |
Soda Feldspar |
100g |
Potash Feldspar |
60g |
|
China Clay |
20g |
China Clay |
20g |
Soda Feldspar |
60g |
|
Whiting |
40g |
Whiting |
40g |
China Clay |
10g |
|
Silica |
60g |
Silica |
40g |
Dolomite |
30g |
|
|
|
|
|
Silica |
40g |
Fire to Cone 8
Method:
1. Make up the above glazes as outlined in 'Glaze Mixing', note that the quantities have doubled to 200g.
2. Use the schedule below to add an amount of colouring oxide:
| Test Number |
1 |
2 |
3 |
4 |
5 |
6 |
| Colour Percentage |
0% |
1% |
2% |
3% |
4% |
5% |
| Amount to Add |
0 |
2g |
2g |
2g |
2g |
2g |
3. Each time you add a colouring oxide the glaze needs to be re-sieved from one container to the
other.
4. Dip a test tile into the glaze in the same manner as we did in 'Glaze Mixing'.
5. Label the test tile with the letters CLB, then the glaze A, B or C, and finally the number of the test.
Analysis:
Use the 'Test Glaze Sheet' to summarise each test series. In particular note the following:
1. The way the colour varies across the series.
2. Any difference in the melt characteristics across the series.
3. The amounts of colouring oxides that were either too much or too little as this gives you the range of possibilities.
4. The way the different base glazes affects the colour.
Summary:
Line blends are a powerful method of finding out the correct proportion of colouring oxide that is needed to colour a glaze. However, they do suffer from an accumulating error problem and so keeping the series of tests short improves their accuracy. |
