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Chemical Reduction Notes

Particle Size Conversion Chart

Tom Turner Chart

 

Chemical reduction notes since the article was published.

It is crucial that a copper red glaze have barium and zink in it. The zink is a strong flux that smooths out the glaze and probably because of the extra melt, the red gets brighter. Barium has the same affect on the glaze. To increase the zink or barium you may have to reduce other fluxes.

The chemically reduced copper red glazes are more crucial to thickness than a reduction copper red.

The firing cycle must be coordinated with the glaze so that melt will capture the reduced copper and to be viscous enough to maintain the reduced red in the re-oxidation of cooling. This was proven when test tiles fired alone provided great reds, but then when a kiln load of pots were fired, the reds went dark and grayish. I assumed that the fuller kiln fired and cooled slower and messed up the reduction re-oxidation process. It did and I increased ramp from 350 per hour to 400 degrees per hour, 2/15/13 and the results were perfect.

Certainly every different formula is going to provide different color and more specifically, different textures and patterns. Each could require a different ramp speed for firing.

Different formulas will require different amounts of copper and silicone carbide due to the beginning of melt and viscosity. 1/3% of copper carbonate and silicone carbide gave the cleanest and brightest reds.

Copper sulphate may produce darker reds, but may also cause grayish black colors from too much reduction.

The larger the SiC particle size, the longer it's melt and chemical combination with the copper.

 

Particle Size Conversion Chart This chart is designed to compare millimeters, microns and inches to sieve sizes and match them to corresponding ANSI grit sizes. 0 5 0 - - -

 Millimeters

Microns

Inches

ASTM Sieve

Tyler Sieve

*ANSI Table 2

*ANSI Table 3

5.60

5600

0.220

3 1/2

3 1/2

S-S

-

4.75

4750

0.187

4

4

4

-

4.00

4000

0.157

5

5

5

-

3.35

3350

0.132

6

6

6

-

2.80

2800

0.110

7

7

7

-

2.36

2360

0.093

8

8

8

-

2.00

2000

0.079

10

9

10

-

1.70

1700

0.067

12

10

12

-

1.40

1400

0.055

14

12

14

-

1.18

1180

0.046

16

14

16

16

1.00

1000

0.039

18

16

20

20

0.850

850

0.033

20

20

22

24

0.710

710

0.028

25

24

24

-

0.600

600

0.024

30

28

30

30

0.500

500

0.02

35

32

36

36

0.425

425

0.018

40

35

40

-

0.355

355

0.014

45

42

46

46

0.300

300

0.012

50

48

54

54

0.250

250

0.010

60

60

60

60

0.212

212

0.008

70

65

70

70

0.180

180

0.007

80

80

80

80

0.150

150

0.006

100

100

90

90

0.125

125

0.005

120

115

100

100

0.106

106

0.004

140

150

120

120

0.075

75

0.0030

200

200

150

150

0.063

63

0.0025

230

250

180

180

0.053

53

0.0021

270

270

220

220

0.045

45

0.0018

325

325

240

240

Micro Grits

Millimeters

Microns

Inches

D3% Max

D50 +/-

D94% Min

ANSI Grit Size

0.0500

50.0

0.00200

74-80

47-53

26-32

240

00395.0395

39539.

000156.00156

67-726772

37-423742

20-252025

280280

0.0295

29.5

0.00116

55-60

27-32

15-19

320

0.0230

23.0

0.00091

38-42

21-25

10.5-14.5

360

0.0183

18.3

0.00072

31.5-35.0

16.5-20

7.5-10.5

400

0.0139

13.9

0.00055

28.0-30.5

12.5-15.3

8.5-8.0

500

0.0106

10.6

0.00042

24.0-27.0

9.2-11.9

-

600

0.0077

7.8

0.0003

20.5-22.5

6.5-8.8

-

800

0.0058

5.8

0.00023

16-18

5.2-6.4

-

1000

0.0038

3.8

0.00015

13.5-15.5

2.8-4.8

-

1200

0.0450

45

0.0018

80

38-52

20

F

0.0275

27.5

0.0011

45-55

23-32

9-16.5

FF

0.0160

16

0.00063

35

12-20

5

FFF

0.0110

11

0.00043

35

11

4

FFFF

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