The degree of dampness which is necessary for transfer may be judged in that the print must feel soft, but the gelatine film ought not to be very sticky. Any further preparation of the print before transferring to the stone is not necessary. The print is laid on the stone, over it a dry sheet, and then the cover, and then drawn through the first time with light pressure.
In order to prove whether the transfer has taken well a corner may be lifted up. All the ink which was on the print must be transferred to the stone, and then the transfer has been completed in the correct way. The print is now pulled off the stone and the transfer made ready, like any other.
With this method of treatment the print will strip easily, which is not the case if it was not well dried after the developing bath; a much sharper and cleaner transfer will also ensue. If the print was too damp a fuzzy, broken-down transfer will be obtained, because the gelatine, which has become too soft, will be broken down.
I will also mention that it is not advisable to treat fine drawings or autotypes with the rubbing-up pad. It is better to go over the transfer with the roller, and the tones are kept cleaner. The stone is then gummed, placed on one side, and allowed to stand some hours before being etched.
For transferring to zinc plates which are to be etched or to be printed from, the bichromated gelatine print should be bathed in a ten per cent. solution of alum, allowed to dry, and then, as previously described, damped, and then transferred under the same conditions as to stone.
It only remains to mention that the stone or zinc plate should not be too cold.
(B.) FAILURES IN THE PHOTO-LITHOGRAPHIC TRANSFERS.
The failures or faults which are met with in photo-lithographic transfer may be caused by various things.
The squashing down rarely happens with photo-litho transfer, because a good photo-lithographic paper will bear a considerable {59} amount of dampness. When, however, it occurs it may be assumed that either too strong pressure or insufficient care in the setting of the stone is the cause. Much more frequently it happens that some parts of the print do not transfer at all, or only in a defective manner. The chief reason of this is that the print was insufficiently damped. This frequently happens if ordinary or gravure prints are to be transferred with photo-lithographic prints. If the printer encloses the impression on the ordinary transfer paper and the photo-lithographic together in the same damp sheet, and if he estimates the degree of dampness from the gravure print, the photo-litho paper will be insufficiently damped and a good transfer will not be obtained from the latter. If, however, he waits till the photo-litho paper is damp enough, the other impressions will be too damp and will squash out in transfer. For such work the print on ordinary transfer paper and the photo-lithographic print should be kept separate, so that the different dampness requisite for each can be regulated.
Another case which frequently happens is that the print is contaminated with particles of dust or other foreign substances. These may be flying about in the air or be on the stone, the roller, or the damping paper. Through this many transfers of fine drawings are rendered useless. Perfect cleanliness of the utensils and the use of the correct ones, combined with a drying-room for the print absolutely free from dust, are absolutely essential for faultless work.