Albumen paper is sensitized by being floated for a time on the surface of this silver solution, albumen side down. For this purpose it is necessary that the solution should be held in a flat dish, like a tray, with sides from 1½ to 2 inches high, and of a size suitable to the size of the sheet of paper to be floated; if a full sheet, then the dish should be 19x24, and may be of porcelain, agate ware, hard rubber, or any other kind that will resist the corrosive action of the silver solution.
Pour the silver solution into the dish; there should be enough to give a depth of at least half an inch. If there is any scum or dust on the surface after the air bubbles have subsided, take a long strip of tissue paper and draw the edge over the surface of the solution, which will remove the scum or any floating dust or air bells that may remain.
Place your paper on a bench or table, albumen up, and with a large tuft of cotton rub the surface, using a light friction over the whole; then turn the sheet of paper over and take between the thumb and first finger of each hand opposite corners diagonally across the paper, holding the corners up and near together; let the sag of the paper sink one end first, until it touches the solution, which can be plainly seen; then let the hands fall until the other end has reached the surface of the silver; then lower the corners gradually, until the paper lies flat on the solution, care being taken that none of the silver solution runs over the edge of the paper to the back.
The corners of the paper may now be gently raised to see if any air bubbles have attached themselves to the surface of the paper; if so, remove them and let the paper fall again to the solution. It will now be seen that the edges of the sides of the paper will begin to curl back, as if repelled from the solution. This may be permitted to a certain extent, but not so far as that the wet surface shall curl over against the back of the sheet. After a short time this action ceases and the rolled edges unroll and fall again upon the solution, which, when they have reached and lie flat, may be taken as an indication that the paper is sufficiently silvered, when it should be removed. With a small pointed stick raise the left corner farthest from you from the solution, take it between the thumb and first finger of the left hand and raise it very slowly, until the right hand far corner is off the solution. Take that corner between the right hand thumb and finger and continue to raise the paper, still very slowly, until it is clear of the solution; then hang it up to dry in a moderately dark place, or better still, place it face down, on a sheet of clean blotting paper, put another sheet over it and on that the next sheet that is silvered, and so on alternate sheets, until you have floated as many sheets as may be needed.
When this is done turn the papers over, bringing the sheet first silvered to the top, which on removing the blotting paper will be found surface dry at least, and may now be completely dried by artificial heat, or by hanging it up two sheets together, back to back, on lines with spring clips, until they dry spontaneously, when they are ready to be fumed.
The fuming box is usually a light-tight box with two compartments; the upper part has a door and should be sufficiently large to hold the amount of paper necessary for a full day's work, without crowding the sheets together or preventing a free circulation of the fumes between their surfaces.
The paper is taken from the lines, each two sheets back to back, the corners fastened with clips and set up on end in this compartment or hung on lines, as the case may be. When all the paper is in, shut and fasten the door and into the bottom compartment (which is usually a shallow drawer, and separated from the upper only by a lattice work of wood) place a saucer containing an ounce or two of strong liquor of ammonia, push the drawer in, thus closing the compartment, and leave for fifteen or twenty minutes, or until you are ready to use the paper.
When you remove the paper from the fuming box do not expose it to strong light until you have it in the printing frames, nor after that, until you have toned and fixed it. Take the spent ammonia from the box and pour it into a bottle; it is useful for other purposes. Many printers cut the paper to size before printing, others simply tear each sheet into halves, quarters, eighths or twelfths, and print them thus, trimming them afterwards, some before toning, others after they are finished and before wetting them for mounting. The most economical method is to trim before printing; all the trimmings should be carefully saved for the silver they contain.