Page:Proceedings of the Royal Society of London Vol 69.djvu/61

Rh Curves from Fleming's " Theoretical " Inks.

though it would be fatal for advertisements or pictures to be exhibited.

Jan. 2. The Pink Ink No. 1303 (Curve No. 3) seems very satisfac- tory, as its absorption begins very rapidly in the orange, whilst the curve rises again fairly high in the blue.

The Blue Ink No. 1265 (Curve No. 4) is far too opaque in the yellow and green. The absorption commences very gradually, and there is also an absorption at the violet end. The ink thus leaves much to be desired. It should rise at about 18 (scale) to 100 per cent., and stay at that to the end, and this it is very far from doing.

The Yellow Ink No. 1271 (Curve No. 5) is very transparent well into the blue, and will probably do well.

Messrs. Fleming also sent me a set of rubbings of the inks they ordinarily supply for photochrome work. These inks are permanent or nearly so :

Photochrome Red No. 1197 (Curve No. 6) has an abrupt absorption rather further in the yellow than the " Theoretical Red," and is so far better, but is far less transparent in the blue, rising at the blue lithium line only to about 5 per cent, as against the 35 per cent, of the " Theoretical Red."

Photochrome Blue No. 1199 (Curve No. 7) rises fairly rapidly, but much too late, namely, in the blue-green instead of the yellow. It will not be possible to make bright greens with this ink.

Photochrome Yellow No. 1198 (Curve No. 8). The absorption is more abrupt than that of the previous yellow, but it is earlier, that is to say, it is not sufficiently transparent to the blue. It ought to occur at about 46 or 50 instead of 32 (scale).

I measured a set of inks which were printed for me by Mr. Gamble, of the Bolt Court School of Photo-lithography. The pink ink (Curve