> which gives great facility to the designer, one adds some gamboge (or

burnt sienna) to the India ink. The ink of Bourgeois, which is compounded

with yellow and can be diluted as easily as India ink, is excellent, so is

also the American ink of Higgins.(3)



As much as possible it is desirable to replace the colored lines

indicating the constructions, the axis, projections, etc., by differently

punctuated lines made with India ink. However, if the use of colors be

obligatory on the original design, one should trace the red lines with

very thick vermilion or sienna, the yellow lines with gamboge, and the

blue and green lines with a thick mixture of Prussian blue and chrome

yellow in different proportions.



One must abstain from applying washes of any tints on the original. If

necessary they should be brushed over when the reproductions are made;

moreover they can be often replaced by cross-lines more or less open, and

the shadowing represented by thicker but not closer lines.



Tracing paper is recommended instead of linen, which latter, on account of

its thickness and granulation, gives less satisfactory results in regard

to the transparency of the ground and the continuity of the lines.



To reproduce a design on ordinary paper--not too thick--or an engraving,

etc., the paper is rendered transparent by rubbing over on the back of the

original a solution of 3 parts in volume of castor oil in 10 parts of

alcohol, by means of a small sponge. When the paper is quite transparent,

the oil in excess is removed by pressure between sheets of blotting paper,

and the paper dried before the fire or spontaneously. The design so

treated is not in the least injured, for it assumes its primitive

condition by dissolving the oil from the paper by immersion into strong

alcohol, which it is necessary to renew once or twice, then rinsing in

alcoholized water if the drawing be in India ink, or simply in water in

the case of an engraving, and finally drying between sheets of blotting

paper.



Instead of an alcoholic solution of castor oil, vaseline can be employed.

The paper is more transparent.



The method by which are made negative drawings, that is, those which can

be used as negative cliches to reproduce the design in black lines on a

white ground, is thus described by Mr. Cheysson, wlio originated it, in a

manual published by the Department of Public Works of France, from which

we have borrowed most of the above instructions for the drawing of designs

suitable for the photo-reproduction processes:(4)



"One can avoid the necessity of making a negative from the original

drawing by transforming the drawing itself into a negative."



"To that effect it suffices to draw with lithographic ink, then to cover

the paper with aniline brown, and, after drying, to wash it with

turpentine oil which dissolves the lithographic ink without altering the

aniline. The lines appear then white on a brown ground impervious to

light (that is, non-actinic). The design is thus transformed into a

negative, and can yield positive impressions with paper sensitized with

silver salts, the ferriprussiate or the bichromate of potash. The

lithographic ink should be very black and the lines well fed."



"When the drawing is finished it is placed on a board lined with sheets of

blotting paper, then one spreads all over it the aniline brown with a

brush, and, lastly, after drying, the paper is carefully rubbed with a

bung of cotton or a rag imbued with turpentine until the lines of the

design are dissolved."



In our practice we have often taken a negative cliche from drawings made

in the ordinary manner, without the aid of the camera obscura (which would

have been too expensive for drawings of a certain size), by simply

printing a proof by contact on plain or albumenized silvered paper, and

fixing, without toning, in a new solution of sodium thiosulphate, then

washing as usual. The proofs thus obtained from designs drawn with an

opaque ink, which allows a long insulation and, therefore, yields an

intense reduction, are of a deep brick-red color, quite non-actinic, and

give very good positives by the Artigues process.



N.B.--Paper in drying never assumes its original shape; it is, therefore,

necessary to make the figures on the reproductions from plans when they

are not on the originals.