In wet-plate photography the plates are prepared as they are required, and are developed immediately after exposure. Any camera may be used so long as provision is made in the dark slide to catch the drippings from the plates; a fold of blotting paper will answer this purpose. The following materials will be required for preparing and developing the plates. Mawson's iodised collodion 4oz., silver nitrate 1 oz., a few pounds of hypo, alcohol 1 oz., acetic acid 1 oz., sulphate of iron 1 oz., an ebonite dipper, and some pieces of clean glass free from air bells. Make up the following solutions.

Silver Bath

Silver nitrate loz., distilled water 11 oz., iodine lgr., nitric acid 2 drops.

Developer

Sulphate of iron 1/4oz., alcohol 1/4 oz , acetic acid 1/4oz., water 4oz. Clean the glass by first swilling with water, and, if greasy, washing with a powerful alkali such as caustic soda, and again swilling. Allow the glass to dry spontaneously. When dry, wipe free of dust, and pour in the centre of the plate a pool of the iodised collodion, as in varnishing a negative, and flow first to the top right-hand corner, next to top left-hand corner, then to the bottom left-hand corner, where the plate is balanced by the tip of the thumb, and from the bottom right-hand corner pour off the excess into the bottle. As soon as the collodion has set (which is when the surface becomes dull) immerse the plate in the silver bath by means of the dipper, lowering gently into the solution, where it should remain, rocking occasionally, for about two minutes. As soon as the silver solution wets the plate evenly (this takes longer in cold weather) the plate is sensitised. The sensitising is done in the dark room, and a flat porcelain dish may be used to contain the bath. The plate is gently removed from the bath, and when it has finished dripping it is placed on the wires in the dark slide and exposed in the ordinary way, though for a longer time than a dry plate.

The plate must be kept in a vertical position. On removal from the slide the plate is held in the hand, as in coating, and is flooded with the developer. Coating the plate, sensitising, exposing, and developing should follow each other as quickly as possible, or various defects will occur in the plate. As soon as development is complete the plate is immersed in hypo 1 oz., water 6oz. The used developer and the drippings should be filtered through cotton-wool and saved for use in cases of over-exposure. Should the image be too weak, it may be strengthened or intensified by flooding with pyro 4gr., water 2oz., silver bath 1 dr., and 10 per cent, solution of .880 ammonia a few drops. Wet plates may be varnished with ordinary negative varnish. The ferrotype is merely the wet collodion process for producing positive images on a metal, instead of glass, plate, the image being reversed as regards right and left. The only advantages of the wet collodion process are cheapness, extreme density and contrast in image, and fineness of grain.

The process, being dirty and extremely slow, is now seldom used except by itinerant photographers.