For wet collodion negatives it is invaluable, as its use entirely does away with split films; and when only 1 or 2 prints are required, the negative need not be varnished with spirit varnish. All that is required, after the negative is washed, is to flood it with the water varnish, and stand up to dry; when dry, the negative is ready for the printer so far as the surface is concerned. A film so protected stands a great deal of rough usage, and is not very easy to scratch, while for retouching the surface it is superb. For wet collodion negatives, the advantages are certain immunity from split films, and saving of time, trouble, and expense of spirit varnish, fire, etc., and risk of cracking the plate from the action of heat.
For gelatine negatives, water varnish is applied directly after they are washed, and, when dry, the retouching is performed, and spirit varnish is applied in the usual way, when there will be little danger of the films being silver stained, no matter how long they are in use.
A gelatine negative, covered with water varnish and dried, was placed upon a shelf, and a cotton-wool plug out of a silver funnel was laid upon the film. At the end of 3 days no sign of a silver stain was visible, and this without any spirit varnish over it. This water varnish will be found fur superior to a film of plain collodion, besides being easier and simpler of application.
One important point in favour of a water varnish is the fact that it can be applied to the film when wet, and therefore with all its pores open; while that part of the varnish that does not sink into the film, but remains upon the surface, will give a gripe or hold for the subsequent film of spirit varnish, affording a promise of security more in accord with the known permanence of a well-varnished collodion negative. (W. T. Wilkinson.)
(7)The following recipe for a retouching varnish is given in the St. Louis Practical Photographer by A. St. Clair: - Best orange shellac, 2 ox.; ammonia carbonate (in crystals), 4 ox.; soft water, 32 oz. Raise the water to nearly boiling point, then add the ammonia, and, when that is dissolved, the lac; stir well until the whole of the lac is dissolved; allow it to cool, and filter.
Apply it to the negative by pouring on and off a few times, and dry thoroughly.
Amber, 1 part; copal, 1; benzole, 2; spirit of wine, 15.
Amber, 2 parts; copal, 2; mastic, 1; petroleum naphtha, 10; spirit of wine, 20.
(11) It was not long after the general adoption of the gelatine process that it was discovered that the varnish hitherto used for collodion negatives was not a sufficient protection in the case of gelatine negatives when large numbers were required to be printed. Minute spots first made their appearance, and these rapidly multiplied and increased in size until the negative became useless. Many methods of treatment were suggested and carefully tested as a protection against the caustic action of the silver salt on the film of gelatine; but suffice it to say that none was found to equal in efficacy a coating of collodion followed by another of spirit varnish; and, judging from subsequent experience, these substances, if properly applied, seem to be a perfect remedy for the evil.
A suitable collodion is made by dissolving a tough soluble pyroxyline, such as is used for surgical collodion, to the strength of 6 gr. to the oz. in equal parts of methylated alcohol and methylated ether *720. It is allowed to settle for some days; and the clear collodion may then be applied to the negative in the usual way. It should not, however, be drained off too closely, but should be allowed to flow back evenly over the surface, and the plate then placed on a level support until set. When dry, a thick impervious coating results, which is rendered hard and proof against ordinary risk of mechanical injury by the application of a lacquer prepared as follows : -
To 1/2 lb. "button lac" and 2 oz. sandarac placed in a flask, add 1/2 gal. methylated alcohol, and shake up occasionally during a week, by which time the soluble portion will be taken up; but do not use artificial heat to dissolve the sediment, as it is better filtered out. Button lac, although apparently browner than shellac, is recommended in preference, as it really gives a lighter coloured solution; but even seed-lac may be used if the precaution be taken after filtration of boiling the clear but dark-coloured varnish for 10 minutes in a flask on a water bath with 4 oz. freshly prepared animal charcoal, which treatment, followed by a second filtration, effectually removes the orange dye which would otherwise tend to retard the printing. The collodionised negative is warmed as usual before and after lacquering. Many negatives thus treated have been in contact with sensitised paper for several months at a time, and exposed in all weathers during the last 3 years without any apparent detriment; so it is hoped that this record may not be without some practical value. (W. Bedford.)
(13) If your pictures are otherwise satisfactory, you need only proceed as follows, to ensure their keeping for printing: - Prepare a weak solution of gum, say 1 oz. gum to 4 oz. water. When your plate is developed, fixed, and washed, and while still wet, pour over it some of the above gum water, and cover the plate with it as with a varnish. Rear up on edge to dry spontaneously. This forms a perfectly protective covering, which never sticks to the albu-menised paper, no matter how hot the sun may be.
(14) Colourless Negative Varnish
Dammar, 2 parts; mastic, 1; sandarac, 0.5; chloroform, 20; tar-varnish oil, 20.
For preparing this varnish, the finely-powdered resins are tied in a small linen bag and suspended from the lower part of the cork in a bottle containing the corresponding quantity of fluids. The solution will be accomplished in a short time if the bottle is put in a moderately warm place. After the resins have been dissolved, the clear varnish is poured off from the uncommonly small quantity of sediment. The process of lacquering the plates with the varnish is very quickly accomplished, as the solvent shows great volatility.
(15) Sandarac...... 4 dr.
Spirit of wine .. .. 20 dr.
Chloroform .. .. 1/2 dr.
Oil of lavender .. 3 dr.
The filtered solution is spread out by pouring it over the glass plate, and dried by applying heat. The coating is perfectly colourless, and negatives coated with this varnish do not crack, even if they are stored away for a long time.
(16) Monkhoven's Retouching Varnish For Negatives
Shellac is placed for 24 hours in a saturated solution of ammonia carbonate in water. The solution is then poured off, and replaced by an equal quantity of pure water; the fluid is boiled under constant stirring until a complete solution has taken place. The proportion between shellac and water should be as 1:8. This is poured twice in succession over the negative, which must be thoroughly dry. Retouching can be done more quickly and finer upon this coating than upon any other.
(17) Retouching Varnish
Shellac .. .. .. 1 oz.
Sandarac .. .. .. 6 oz.
Mastic .. .. .. 6 oz.
Ether ...... 10 oz.
Then 10 oz. pure benzole are added to the mixture after the resins have dissolved in the ether.
(18) Hard Lacquer For Negatives
Sandarac...... 20 dr.
Venetian turpentine 2 dr.
Oil of lavender.. .. 2 1/2 dr.
Ether ...... 2 1/2 dr.
Absolute alcohol .. 50 dr.
Mastic ...... 2 dr.
Bleached shellac .. 10 dr.
Oil of turpentine .. 2 dr.
Spirit of wine .. 60 dr.
(20) Collodion, by itself - even the ordinary porous collodion employed in negative work - answers admirably. As a protection against damp, its effect is simply marvellous; for, should the moisture penetrate it and reach the gelatine film, it possesses sufficient elasticity to withstand the strain put upon it. It exhibits little tendency to absorb silver from the damp printing paper, and in the event of actual moisture being accidentally present when in contact with the paper there is no fear of adhesion. For portraiture, the film will bear working on with the pencil in retouching, though from its hardness and smooth surface it is usually desirable to use a "medium" to give a "tooth" which will take the pencil.
In preparing a special collodion for the purpose, select a good, tough - not necessarily "horny" - sample of pyro-xyline, and use it of the strength of not more than 4 gr. to the oz., with 2 or 3 drops of castor oil. The best protective medium consists of a collodion made from celloidine, which gives a remarkably clear and structureless film, and may be used stronger than ordinary pyroxyline: 5 gr. celloidine and 2 drops of castor oil to each oz. of solvents will answer well. There is a slight advantage in employing a small excess of ether over alcohol in dissolving - say 9 parts ether to 7 of alcohol - both being as free from water as possible, and the negative very thoroughly dried before application.
(21) For Wet-Plate Negatives
White hard varnish .. 1/2 pint Methylated spirit (about) 1 pint.
Try plate. If too thick, add more spirit. This will be found a capital varnish for retouching purposes.
(22) For Dry Plates
Red shellac varnish .. 1/2 pint Methylated spirit (about) 11/2 pints.
Try a plate, and add or lessen spirit according to requirements.
(23) Fritz Luckardt's Retouching Varnish
Alcohol ...... 300 parts
Sandarac •• .. .. 50 "
Camphor .. .... 5 „
Castor oil...... 10 "
Venetian turpentine .. 5 „
(24) Varnish To Imitate Ground Glass
Sandarac ...... 18 parts
Mastio........ 4 „
Benxole .. 80 to 100 "