A Manual Of Photography

THE USE OF ALBUMEN ON GLASS PLATES AND ON PAPEN. 281 the face a moderate quantity of fine tripoli, moistened with a few drops of a concentrated solution of carbonate of potash; then with a piece of cotton wool rub the surface briskly in circles for about five minutes; then with dry tripoli; then with clean cotton to clear away all the dusty particles. “ Third. To the centre of the back stick a gutta percha ball, as a handle: strain the prepared albumen through clean linen; pour it gently into the centre of the cleaned side of the glass, keep it moving until the surface is entirely covered, run it into the corners, and finally pour off any excess at the four corners; disengage the gutta percha handle, and place the glass on another slab, that has been levelled by a spirit level, in a place perfectly free from dust, and moderately warm. I will call this my iodo- albuminized glass; it will keep for any length of time, and may be prepared in daylight. “Fourth. To excite (a yellow shaded light only being used), dissolve 50 grains of nitrate of silver in 1 ounce of distilled water and 120 grains of strong acetic acid; pour the whole of this so- lution into a cuvette, or shallow porcelain dish, a little larger than the glass plate ; place one end of the iodo-albuminized glass in the solution ; with a piece of quill support the upper end of the glass, and let it fall suddenly on to the solution, lifting it up and down for ten seconds ; take it out and place it face upwards in another dish, half filled with distilled water; allow the water to pass over the surface twice ; take out the glass, rear it up to dry ; it is ready for the camera, and will keep in this state ten days,—of course, shut up from daylight, in a moderately warm place, but never moist. The solution may be filtered into a black bottle, and will do again by now and then adding a few drops of acetic acid, and keeping it in the dark. Expose in the camera from four to ten minutes, accord- ing to the amount of light and the aperture of the lens. Sup- pose I say a lens of three inches diameter, sixteen in focus for parallel rays, a one inch diaphragm placed three inches in front of the lens (one of Ross’s photographic lenses is just the thing), the exposure would be in good light about five minutes. "Fifth. Develop as follows. Place the glass, face upwards, on a stand with adjusting screws to make it level; pour a con- centrated solution'of gallic acid over the surface ; the image will be from half an hour to two hours in coming out. It is best to apply a gentle heat, not more than 10° above the temperature of the room, it being 60°. Should the image still be feeble, pour off the gallic acid, rinse the proof with water, and pour on to it equal quantities of aceto-nitrate of silver and gallic acid reduced one half with water. The image will now quickly de-