34 



PHOTO-MICROGRAPHY 



to make this equality in the distribution quite certain. The plates must be covered 

 during the whole process of development (especially the isochromatic ones) and the 

 three-coloured window well closed whilst the plates are put into the slide and during 

 the first portion of development. To obtain perfectly clear and clean unfogged 

 negatives with his isochromatic plates, Mr. Edwards quite rightly insists on the 

 necessity of having a dull red light and, moreover, that the plates shall be well covered. 

 When " backed" plates are used — and we believe that every plate, whether for land- 

 scape work or photo-micrography, should always be so treated — it is best to wipe 

 the backing off before placing in the developing dish, and we have found it a handy 

 plan to have a piece of rag kept in the sink in one place for that especial purpose. 



All during development the dish should be rocked to and fro and from side to 

 side, the negative being looked at as little as possible, and then only for a moment 

 to note how the process proceeds. After about a minute or a minute and a half — a 

 longer time in winter — the image comm,ences to appear on Edwards's iso-medium 

 plate, the bright parts of the original object of course showing first and the details 

 following after. When these begin to become apparent, say after about five minutes, 

 one or two of the shutters may be opened and the negative somewhat carefully 

 examined, especially the back of the plate. 



If during development the picture " TUshes up " with great rapidity, it is sure to 

 have been over-exposed : at once put in the developer two, four, up to twenty or even 

 thirty drops of the Bromide Solution according to the rapidity in question. Here 

 most decidedly practice is needed. Always develop until the image is well seen on 

 the hack, and let it be remembered as a guide that if the image comes through very 

 quickly the plate is under exposed ; if slowly and steadily, rightly exposed ; if it 

 hardly will come through at all, over exposed. 



Developing a negative is an art, and cannot easily be written about because it is 

 impossible to find words exactly fitted to describe the different appearances. For 

 this division of our subject what we have said seems sufiicient, but as development of 

 medium-ipower w^ork and high-ipower -work each offer certain peculiarities in them- 

 selves, we shall refer again to the subject a little later on. 



After washing the negative it is placed in the " hypo " bath as it is called, a dish 

 containing hypo-sulphite of soda dissolved in water. The exact proportions of the 

 crystal to water does not seem to matter, but a too concentrated solution works very 

 slowly, almost as much so as a too diluted one. 



After leaving in the " hypo " for a little time all the yellowness of the plate is 

 dissolved out and the negative is said to be "fixed," as light will have no further 



