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398
Transactions of 8.M.P.E., Vol. XIII, No. 38, 1929
negative film is not rinsed in water and allowed to fix without agitation, this produces in effect, a fixing bath having a high concentration of sulfite in the gelatin layer whose hardening properties are at a minimum. It is very important, therefore, in the case of film developed in the Eastman borax developer, to agitate thoroughly on first immersing in the fixing bath otherwise little or no hardening will be produced and reticulation is likely to occur in hot weather.
Table IV
Effect of Exhaustion and Revival with Acid on the Time
of Fixation and Degree of Hardening
Betic. Pt.* Film Time to Clear M.P. Neg. Film Fixed M.P. Neg. Film Fixed 15 Min.
Time to Clear M.P. Pos. Film
Melting Point M.P. Pos. Film Fixed 5 Min.
pergal. A
S
WE
0
3' 50"
6' 50"
118°F.
50
4' 30"
7' 50"
118°F.
100
5' 30"
8' 30"
128°F.
150
6' 30"
9' 45"
133°F.
200
r 30"
11' 30"
140°F.
250
9' 15"
13' 30"
140°F.
300
10' 00"
16' 15"
350
400
450
500
550
600
650
700
Key to abbreviations: A —
vival
: AE— After Eevival.
AE
128°F.
140°F.
A
30 sec.
35 sec. 40 sec. 47 sec. 60 sec. 70 sec.
S
70 sec.
85 sec.
95 sec. 105 sec. 125 sec. 155 sec. 200 sec.
WE 150°F.
160°F.
110°F.
135°F.
142°F.
141°F.
128°F.
AE
160°F. 168°F. 152°F. 156°F.
148"i'.
100 sec. 240 sec. 128°F. 135°F. Agitation; S — Stationary; WR — Without Re
* In the ease of negative film the melting point is somewhat indefinite when determined in water and the temperature at which the gelatin ' ' puckered ' ' or reticulated is recorded.
With machine development the agitation is adequate. Hardening data for the above bath during use when fixing negative film developed in the Eastman borax developer with agitation are shown in Table IV.
4. Revival of the Bath with Acid. An alum hardening fixing bath is usually rendered useless as a result of the formation of a precipitate of aluminium sulfite long before the fixing properties of the hypo are exhausted. A fixing bath can, however, be revived sue