Defects Due To Damp

All plates should be kept in a dry place, and whilst travelling it is as well to keep them in tinfoil. The effect of damp is to produce patches, which either do not develop at all or develop unequally.

Removal Of Varnish

This is easily done by putting the plate into hot methylated spirit, and rubbing the varnish off with cotton wool.

Sea Air

It has been said that sea air affects gelatine plates, this has not been our experience.

Dirty-Backs

The backs of the negatives which are generally dirty, should be cleaned by scraping, and then rubbing up with a rag moistened in hot water, or preferably, methylated spirit. The negatives should be kept in a dry place, in grooved cardboard boxes. Wooden boxes should not be used for storing either plates or negatives.

Marblings

Are due to a dirty fixing bath; or to an uneven action of the developer arising from not rocking the plate, or to adding the alkali to the developer in the dish and not thoroughly mixing them before putting in the plate. The clearing solution removes some of these.

Prolonged And Patchy-Fixing

Due to the alum bath being used before "Fixing" in plates from which the developer has not been thoroughly washed. It can be remedied by washing and swilling the plate in water just rendered alkaline by ammonia, and then fixing as before. We once had a plate which took several hours to fix even after this treatment.

Limpet Shell Markings

Deposit on film.

We have had these appear in a few negatives some months after development. We know of no remedy for the defect; nor do we know the cause, but believe it to be due to hyposulphite of soda left in the film.

This is sometimes met with after the imperfect washing out of hyposulphite of soda; or sometimes whilst the negative is in the fixing bath, if it has been in the alum bath previously, and not thoroughly washed. Sulphur is deposited. The remedy is obvious.

Metallic Patches

Coloured metallic-looking patches appear at times near the edges of the plate, which may, or may not, be accompanied with fog. We have often observed these patches in plates which have been kept a long time. There is no remedy if they are unaccompanied by fog, but if fog is present, the ferric-chloride solution will generally remove them.

Scratches

On the back of the negative show as dark lines in the film.

Undeveloped Islands

Rarely, we have met with small patches which seem to have refused to develop; they are generally circular. Captain Abney says they are due to the use of chrome alum in the emulsion. There does not appear to be any remedy for this accident.

Dull Spots And Pits

In one batch or plates we were greatly troubled by these faults, one of the plates being covered with pits as thickly as if it had been peppered with a pepper-box. Captain Abney says they are due to the use of gelatine which contains grease. They ruined a whole series of fine negatives for us once. These complete the enumeration of the accidents likely to occur during development.

Varnishing

We shall now presume that the student has thoroughly dried his negatives, after having developed them. Before storing them, however, he must varnish them, to protect them from scratches, and especially from damp, for gelatine, being very hygroscopic, easily absorbs moisture. At times, when warming an apparently perfectly dry negative over a flame, preparatory to varnishing it, a slight steam can be seen to arise, due to the evaporation of the moisture in the film. This moisture in the gelatine would of course in time lead to decomposition, and ruin the image; for these reasons, then, all negatives should be varnished. Before "varnishing" each negative should be carefully brushed over with a camel's-hair brush. Now it is obvious that many of the varnishes used are more or less non-actinic, as Dr. Carey Lea has proved; he, therefore, recommends the following: -

Dr. Carey-Lea's Varnish

Dr Carey Lea s Varnish images/NaturalisticPhotography 10

Bleached lac......

3

X.

Picked sandarac ......

3

V.

Alcohol.......

Dr Carey Lea s Varnish images/NaturalisticPhotography 11

xii.

Let the lac dissolve in the alcohol, then filter, first soaking the filter paper with alcohol. Pour slowly, and if necessary at the end add 1 5 more of alcohol to enable the rest to pass. Next add the sandarac to the filtrate and refilter, using of course a fresh filter.

Warm the plate gently, and, holding it in the left-hand bottom corner between the thumb and finger, pour a pool of varnish on to the plate that will cover about one-third the area of the plate, then let it run to the right-hand top corner, then to the left-hand top corner, then to the thumb, and finally drain off at the right-hand bottom corner into a filter. Then place it on a drainage rack, till just set, when re warm by the fire, otherwise it does not set hard and smooth.

Roller Slide And Paper Negatives

Since paper negatives and a roller slide were suggested by Fox Talbot, and made fit for use by Blanquart-Evrard, several ingenious persons have been trying to improve upon these early attempts. From time to time, during the last fifty years, various workers have announced old ideas as new discoveries, nor have these been confined to roller slides and paper negatives, but extended to many other photographic processes. That no one can claim any originality of discovery on this head since Talbot and Evrard is obvious; only perfected methods can be claimed. There have been many of these introduced, but none worth discussing until that offered by the Messrs. Walker and Eastman. They have perfected Talbot's and Evrard's work, and though they have numerous imitators, their work is facile princeps.

Paper Negatives

Now the student will naturally expect us to give an opinion on these paper negatives. For many photographic processes they are of course invaluable, but for artistic work our opinion is that they are not equal to the ordinary method. These remarks apply equally to the various flexible films which have lately been introduced.