1105. The only difficulty in the original method of developing Autochrome plates was the impossibility of correcting errors in exposure by modifying the composition of the first developer and time of development. To overcome this difficulty the Lumiere people have experimented to secure a dark-room illumination of such low actinism as to permit to follow, with due precautions, the appearance of the image during development without fear of fogging.

1106. Another marked improvement is the new developer, which is susceptible of being modified during development according to the time of the appearance of the image, which time, given the same developer at the same temperature, is governed by the exposure.

1107. The developer, formula for which follows, when poured on the plates, greatly reduces their sensitiveness to the radiations of the new lighting, and makes it possible to watch the appearance of the image, and, according to the time of appearance, modifies the composition of the developer and regulates the time of development.

1108. Lighting of the Dark-room. A 16-candle power electric bulb, gas jet, kerosene lamp or candle may be used as the source of light. It should be enclosed in a lantern having only one illuminating surface, composed of sheets of "Virida" papers held between two sheets of plain glass. The "Virida" papers are specially prepared by the Lumiere people for this purpose.

1109. With a bright source of light, such as a 16-candle power electric bulb or gas jet, superpose two sheets of green paper and three of yellow, the latter being on the inside. With a weak source, such as oil lamp or candle, two sheets of green and two of yellow are sufficient. The light passing through "Virida" papers, although highly inactinic, gives a fairly good illumination. It is imperative that the lantern be perfectly light-tight and only emit light filtered through the "Virida" papers.

1110. We call special attention to the fact that when entering a weakly lighted dark-room, the eyes still vividly impressed with the daylight, take a little time to become accustomed to the new feeble illumination. It is therefore specially advisable to wait a few minutes before beginning development, otherwise one may not properly judge the exact time of appearance of the image.

1111. Simplified Development. By the new simplified method of manipulation the number of solutions have been reduced from six to two, and the operations for the whole process of development to three only. For the new process prepare the following:

1112 - Metoquinon Stock Solution.

Apoth.

Water (distilled preferred)...........................

30 ozs.

Metoquinon (Lumiere's)...............................

3 1/2 dr.

Sodium Sulphite (dry).....................................

3 ozs.

Ammonia (density 0.923)................................

1 oz.

Potassium Bromide.........................................

1 1/2 dr.

Dissolve the metoquinon first in luke warm water, and then the other chemicals in order given.

1113. The two solutions to be used for this simplified method of development are:

NO. 1 DEVELOPER.

Metoquinon Stock Solution ...............

6 dr.

Water ...................................

3 oz.

No. a or C Reversing Solution.

Water .......................

50 ozs.

Potassium Permanganate...........................

50 grs.

Sulphuric Acid...........................................

4 drs.

Ca

This solution keeps better made up in two parts

Water.................................................................

25 ozs.

Potassium Permanganate........................................

50 grs.

cb

Water ...................................

25 ozs.

Sulphuric Acid....................................................

4 drs.

The reversing solution is then made up at any time for use, by mixing equal quantities of Ca and Cb.

1114. First Development. After exposure on the glass side, using the special ray filter as explained in paragraph 1036, the plate is developed in Solution No. 1, using 3 1/2 ozs. for a 5 x 7 plate. For a correctly exposed plate development should last exactly 2 1/2 minutes, the temperature of the solution being at 60° Fahr.

1115. Examining Plate During Development. When development has proceeded for 25 to 30 seconds, the plate may safely be examined by the light of a lantern fitted with the "Virida" papers. If the image shows over-exposure the duration of development should be reduced; increase the time of development for under-exposure.

1116. Reversing the Image. When development is complete quickly rinse the plate; then place it in Solution No. 2 and carry the tray out in full daylight. The plate clears progressively, showing the colors by transparency. The complete clearing takes 3 to 4 minutes. Then the plate is rinsed in running water for 30 to 40 seconds.

1117. Avoid Frilling. In order to avoid any chance of frilling in hot weather, it is a good precaution to immerse the plate after reversal, for 2 minutes, in a 1% chrome alum solution.

Water ..................................

10 ozs.

Chrome Alum..................................................

50 grs.

1118. Second Development. After a brief rinsing the plate is again developed (still in full daylight) in the same solution, No. 1, in which the first development took place, which solution should be kept in the tray for this object without any special precaution. The development should be prolonged for 3 to 4 minutes until the white parts of the image have completely turned black; then rinse the plate for 3 to 4 minutes in running water,, place to dry, without fixing, and varnish.

1119. Intensifying. When, owing to over-exposure, the image is too light and lacks vigor, it can be improved by intensification after the second development. In this inten-sifier use the formula given in paragraph 1049.

Solution F........................................

3 ozs.

Solution G........................................

2 1/2 drs,

1120. Immerse plate and follow intensification by looking through it. from time to time, by transmitted light. As soon as the solution becomes yellow and muddy it must be thrown away and replaced. Intensification is generally complete before the discoloration appears, but if not, a fresh solution is to be used. Before proceeding to this second intensification the plate should be rinsed briefly, then immersed for a few seconds in solution E and rinsed again. During intensification the whites may turn yellow, but any discoloration is entirely removed in the clearing solution.