132 
PRACTICAL PHOTO-MICROGRAPHY. 
Gelatino-chloride Papers 
are sold under various names, but we may take as 
probably the best, and as representing the others, the 
“ Solio ” paper of Kodak Limited, though doubtless 
other papers of the same nature may work equally well 
in some hands. 
The paper, previously surfaced with an insoluble and 
impermeable layer of a barium compound, is coated 
with an emulsion of silver chloride in gelatine ; when 
the emulsion is exposed to daylight it darkens ; 
the colour at this stage is unsightly, and the image 
requires to be “fixed.” The most rapid way to finish 
the operations is to “tone” and “fix ” in one bath, and 
this is easily accomplished ; but the colour is likely to 
be of a somewhat warm kind unless the sulphocyanide 
bath is used, which we consider inferior in most respects 
to the baths we shall recommend. But we may obtain 
good black tones, which are probably preferable for our 
particular work, by the use of other toning baths which 
shall be given. 
This is a “ printing-out” process, i.e., the paper and 
the negative are exposed to daylight, and the image 
becomes plainly visible on the paper. It is also a 
“ contact ” process, because the face of the paper is 
placed in contact with the face of the negative for 
printing. The only apparatus required is a “ printing 
frame,” well known in ordinary photography; the back 
is hinged, and so made that one half of the back can be 
turned away from the paper, and one half of the print 
can be examined without disturbing the position of the 
