232 PRACTICE OF PHOTOGRAPHY.

plunged into it, one over the other, removing any air-bubbleswhich may form. Fifteen or twenty sheets being placed in thebath they are allowed to soak for half an hour, or an hour, ac-cording to the thickness of the paper. Turning over the wholemass, commence by removing the first sheet immersed, andhooking it up by one corner with a pin bent in the shape of theletter S, fix it on a line to dry, and remove the drop from thelower angle by a little bundle of blotting-paper. DM. Le Graythen remarks that French and English paper should never bemixed in the same bath, but prepared separately, as the“ English paper contains a free acid which immediately precipitates aniodide of starch in the French papers and gives to them a viole$tint.” The paper being dry is to be preserved for use in a port-folio; even in this state it 1s not absolutely insensible.

Third Process: To render the Waxed Paper Sensitive.—Make a solution of

Distilled water...... 2325 grains.

Crystallized nitrate of silver.. 75©and when this is dissolved add of

Crystallized acetic acid... 186 grains.

Papers prepared with this solution will keep well for a fewdays. DM. Le Gray, however, recommends for his waxed paper,and for portraits, that the quantity of nitrate of silver beincreased to 155 grains: the paper must be used moist.

The method of preparing these papers is to float upon anhorizontal plate of glass either of the above solutions, and takinga piece of the iodized paper, to carefully place it upon the fluid,taking great care that no air-bubbles interpose. The paper mustremain a short time in contact with this sensitive fluid untilchemical combination is effected. Four or five minutes arerequired for some papers, and eight or ten seconds are sufficientfor other kinds. When a violet tint appears this should beremoved.

For those papers which it is desirable to keep for some time,as during a journey, it is recommended that into one vessel ofporcelain you put about five or six millilitres of the strongaceto-nitrate above described, and into another some distilledwater: you plunge completely both sides of the waxed andiodized paper in the first fluid, and allow it to remain about fouror five minutes; withdraw it, and plunge it immediately into thebath of distilled water, in which let it soak for not less than fourminutes. When these papers are carefully dried they may bepreserved for some time for use, and by lessening the dose ofnitrate of silver this period may be considerably prolonged. It