Gaffer® Casting Crystal Annealing Schedules. Semi-Open and Open Forms *

Thickness


(inches)
(mm)		 Anneal
Soak
Time
@ 806oF
@ 430oC		 Initial
Cooling
Rate
oF/Hr
oC/Hr		 Initial
Cooling
Range
oF
oC		 Second
Cooling
Rate
oF/Hr
oC/Hr		 Second
Cooling
Range
oF
oC		 Final
Cooling
Rate**
oF/Hr
oC/Hr		 Final
Cooling
Range
oF
oC		 Total
Elapsed
Time
.5 in 
12 mm		 2 hr 120
67		 806 - 680
430 - 360		 240
133		 680 - 590
360 - 310		 720
402		 590 - 70
310 - 21		 4hrs 10mins
.75 in
19 mm		 3 hr 52
29		 806 - 680
430 - 360		 104
58		 680 - 590
360 - 310		 312
174		 590 - 70
310 - 21		 8hrs
1.0 in
25 mm		 4 hr 29
16		 806 - 680
430 - 360		 58
32		 680 - 590
360 - 310		 174
96		 590 - 70
310 - 21		 13hrs
1.5 in
38 mm		 6 hr 13
7.2		 806 - 680
430 - 360		 26
14.4		 680 - 590
360 - 310		 78.0
43.0		 590 - 70
310 - 21		 26hrs
2.0 in
50 mm		 8 hr 7.8
4.3		 806 - 680
430 - 360		 15.6
8.6		 680 - 590
360 - 310		 46.8
25.8		 590 - 70
310 - 21		 41hrs 30mins
2.5 in
60 mm		 10 hr 5.2
2.9		 806 - 644
430 - 360		 10.4
5.8		 680 - 590
360 - 310		 31.2
17.4		 590 - 70
310 - 21		 2 days 13hrs
3.0 in
75 mm		 12 hr 3.3
1.8		 806 - 644
430 - 340		 6.6
3.6		 644 - 554
340 - 290		 19.8
10.8		 554 - 70
290 - 21		 4 days 5hrs
3.5 in
88 mm		 14 hr 2.5
1.4		 806 - 644
430 - 340		 5.0
2.8		 644 - 554
340 - 290		 15.0
8.4		 554 - 70
290 - 21		 5 days 12hrs
4.0 in
100 mm		 16 hr 1.8
1.0		 806 - 644
430 - 340		 3.6
2.0		 644 - 554
340 - 290		 10.8
6.0		 554 - 70
290 - 21		 7 days 8hrs
4.5 in
113 mm		 18 hr 1.6
0.9		 806 - 644
430 - 340		 3.2
1.8		 644 - 554
340 - 290		 9.6
5.4		 554 - 70
290 - 21		 8 days 5hrs
5.0 in
125 mm		 20 hr 1.3
0.7		 806 - 644
430 - 340		 2.6
1.4		 644 - 554
340 - 290		 7.8
4.2		 554 - 70
290 - 21		 10 days 9hrs
5.5 in
138 mm		 22 hr 1.1
0.6		 830 - 644
430 - 340		 2.2
1.2		 644 - 554
340 - 290		 6.6
3.6		 554 - 70
290 - 21		 11 days 20hrs
6.0 in
150 mm		 24 hr 0.9
0.5		 806 - 608
430 - 320		 1.8
1.0		 608 - 518
320 - 270		 5.4
3.0		 518 - 70
270 - 21		 16 days
6.5 in
165 mm		 26 hr 0.7
0.4		 806 - 608
430 - 320		 1.4
0.8		 608 - 518
320 - 270		 4.2
2.4		 518 - 70
270 - 21		 19 days 20hrs
7.0 in
175 mm		 28 hr 0.6
0.33		 806 - 608
430 - 320		 1.2
0.66		 608 - 518
320 - 270		 3.6
2.0		 518 - 70
270 - 21		 23 days 19hrs
7.5 in
190 mm		 30 hr 0.5
0.3		 806 - 608
430 - 320		 1.0
0.6		 608 - 518
320 - 290		 3.0
1.8		 518 - 70
270 - 21		 26 days 6hrs
8.0 in
200 mm		 32 hr 0.47
0.26		 806 - 608
430 - 320		 0.94
0.52		 608 - 518
320 - 270		 2.8
1.56		 518 - 70
270 - 21		 30 days 4hrs
8.5 in
215 mm		 34 hr 0.41
0.23		 806 - 608
430 - 320		 0.8
0.46		 608 - 518
320 - 270		 2.4
1.4		 518 - 70
270 - 21		 33 days 21hrs
9.0 in
225 mm		 36 hr 0.35
0.2		 806 - 608
430 - 320		 0.7
0.4		 608 - 518
320 - 270		 2.1
1.2		 518 - 70
270 - 21		 38 days 22hrs
9.5 in
242 mm		 38 hr 0.32
0.18		 806 - 608
430 - 320		 0.64
0.36		 608 - 518
320 - 270		 1.9
1.1		 518 - 70
270 - 21		 42 days 6hrs
10.0 in
254 mm		 40 hr 0.29
0.16		 806 - 608
430 - 320		 0.58
0.32		 608 - 518
320 - 270		 1.74
0.96		 518 - 70
270 - 21		 47 days 15hrs

*  Based on: Schedules for commercial annealing of ordinary ware. Corning Glassworks. Corning N.Y. 1950. For forms that are able
    to cool reasonably equally on all sides.
** Obviously cooling rates of thinner pieces are faster than ordinary kilns would lose heat. In those cases the kiln can be allowed to
    cool at its normal rate.
Revised schedules August 2010.
 
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