B—500 c.c. water plus 5 c.c. formaldehyde for 12 hours
C—500 c.c. water plus 10 c.c. formaldehyde for 3 hours
D—As in C, but treated with 500 c.c. water plus 5 c.c. ammonia, instead of water alone.
Table V
| A S.P. | B S.P. | |
|---|---|---|
| C. | C. | |
| Persian Lamb | 44° | 54° |
| Astrachan | 47° | 55° |
A—Before dyeing
B—After dyeing
As a result of these experiments it may be concluded that the maximum temperature for drying salt-acid tanned skins should be 40° C., while for chamois tanned skins the temperature may be permitted to reach 45° C. without any danger of the leather being affected. Moreover, in the case of pickled skins, the matter of extraction of the tanning agent, as well as that of the leather becoming “burned” may be effectively counteracted by brushing some oil or fat on to the leather side before dyeing the pelt.
The shrinking points of skins dressed by the various tanning methods are constant within certain limits, depending on the nature of the skin and on the conditions of tanning, and it is possible by observing the shrinking point, in conjunction with other characteristics of a given pelt, to determine what method of tanning was used.