3135. To Copy an Object

3135.     To Copy an Object. Having prepared, in a dark room, a sheet of paper as above, lay it upon a piece of glass; place upon the glass a leaf as translucent as can be found, and then above it, to hold it in place, another piece of glass, and at each corner a clip, or a common spring clothes-pin. Now expose the plates so arranged, leaf side up, to the sun's rays. The paper will at once begin to darken, and in from 5 to 10 minutes, except under the leaf, be entirely black. If the plates are now taken into a dark room and separated, the image of the leaf, with all its delicate tracery and beautiful lines, will be found upon the paper, white, with black background. It would be well to put under the sensitive paper a few thicknesses of soft paper, or black cotton velvet. It serves as a pad or cushion, and tends to press the paper up into a closer contact with the inequalities of the leaf, lace, or object used as a negative or cliché Small printing frames can" be purchased at a moderate sum, which will enable the experimenter to examine the progress of the work and ascertain when the print is sufficiently exposed to the action of the light. The exposure should continue until the image is much darker than intended when finished, as the after processes of toning and fixing reduce or bleach the pictures very considerably. As the prints are taken out of the frame, put them away in the dark again, until ready for the toning bath.

3136. To Prepare a Picture for Toning and Fixing

3136. To Prepare a Picture for Toning and Fixing. It will now be necessary to tone and fix the picture, in order that the image be rendered permanent. The first process is to soak the print in a dish of clear water for a few minutes, and thus wash off the free nitrate of silver remaining upon the surface of the paper. A half hour's soaking, with one or two changes of the water, will effect this so that it is ready for the toning bath.

3137. To Prepare a Toning Bath

3137.    To Prepare a Toning Bath. Chloride of gold is sold in bottles containing 15 grains. Dissolve this in 30 drachms of water, add a drop of hydrochloric acid, and preserve it as a stock solution in a bottle; mark this gold solution. Make in another bottle a saturated solution of washing soda, also as a stock solution; mark it as such: Soda solution. When the prints have been washed as before directed, and are ready for toning, mix 1 drachm of the gold solution with 1 ounce of water, according to formula. Pour into a tray, and drop in a small piece of blue litmus paper; it will become red. Render the bath alkaline by adding from the soda solution, drop by drop, until the paper begins to change blue again. It is better to prepare the toning bath during the day, while the printing is being done, as the bath seems to work with more smoothness and uniformity. It may be used, however, so soon as mixed.