This is not the cheapest method of working, but the author has proved it in practice to be one of the most reliable, and when one considers that the actual cost of the dye and drying alcohol is approximately $2.00 for thirty plates it is not a serious item.

There are, of course, all sorts of variations of this procedure. For instance the whole 400 ccm of dye may be put into the dish at once, and poured out into a graduate at the end of the time required to sensitize each batch of plates, and more alcohol may be used or a fresh batch each time; or the plates may be lifted out of the dye solution and placed in another dish for the alcohol bath; but the less the plates are handled the easier the work becomes. As already stated either ethyl or methyl alcohol may be used; denatured spirit is dangerous unless one knows what the denaturant is, and should be avoided. There is one point that has not been mentioned and it is extremely important. If the sensitizing and drying is carried on in a room that is used for ordinary work, such as developing and fixing, it may be taken as an axiom that it is impossible to prevent insensitive and other spots occurring. The drying fan draws the air from the room and any particle of hypo settling on the damp surface will cause an insensitive spot, while developer dust will give rise to black ones. The dimensions of the drying tunnel should be kept as small as possible, taking into consideration the size of the drying racks. These can, as a rule, be cut down considerably in height, as the legs can usually be shortened. The smaller the tunnel within reason, the more the air is confined and, therefore, the quicker the drying.

Taking all things into consideration, there can be no question that for the beginner in color work commercial plates are preferable. Their keeping power is certainly much greater, one is certain of having them free from drying spots and stains, and most of the makers issue with each box a card that not only tells one the correct ratio for the filters, but also the correct time of development to obtain a given degree of contrast. Above all things, one can obtain them backed, and thus there will be saved one of the worst jobs for the home worker. A backed plate gives much better results than an unbacked one, if the proper backing is used, and as the plate is sensitive to all colors it is obvious that the only efficient backing must be black. It is not a difficult matter to make a black backing, and one the author has used for years is:

Dextrine 100 g.

Water 100 ccm.

Heat till dissolved and then stir in:

Ivory black, water color paste 1000 g.

Continue stirring until thoroughly incorporated. As this is sufficient for a large number of plates and it is apt to mould if kept, it is advisable to stir in about 10 ccm of phenol (carbolic acid).

There is no lack of commercial panchromatic plates, as Eastman Kodak Co. (Wratten & Wainwright), the Ilford Co. and the Cramer Dry Plate Co. all issue plates of excellent quality and color-sensitiveness, which may also be obtained backed on request. It would be invidious to single out one particular make as better than the others and also unfair; but naturally most workers have their own pet brand, as every smoker favors one particular tobacco. The author in no wise differs in this respect, but his favoritism is based on many years' use of one particular brand and while there is very little logical reason for it, he always thinks that he can obtain better results with this particular make. Plates certainly differ in their characteristics; assuming that they all have the same color-sensitiveness, the chief differences lie in the velocity constant of development, and increase of fog with time of development. The old advice that has so often been given for ordinary work applies with equal force to color work; that is, choose one plate and stick to it.

As regards the use of film for color separation work, the only plan that can be adopted is to use commercial panchromatic film and it must be in one piece. The author's experience has proved that to use three separate films is almost a hopeless task, in consequence of the unequal expansion and contraction of the celluloid making it practically impossible to obtain correct superposition of the images. On the other hand, if this must be used and the worker is determined to sensitize it himself, the same sensitizing baths may be used, but the alcohol bath must be omitted, or the film will either roll up into a tight spill that is utterly useless, or will be so distorted by partial solution of the celluloid as to be quite unworkable. The sensitizing bath can be somewhat improved by the replacement of 10 per cent of the water by the same volume of methyl alcohol, and after sensitizing, the film should be washed for ten minutes in frequent changes of distilled water to which 0.2 per cent of borax has been added.