DEVELOPMENT OF THE PLATE. 
123 
bath. If, perchance, there are symptoms of the film 
“ frilling,” or puckering at the edges, the plate may be 
put before fixing into a bath of water saturated with 
common alum. Few plates frill nowadays, and any 
that do should be rejected. 
The Fixing Bath. 
lake sodium hyposulphite 1 part by weight, and 
water 5 parts by measure. It is quite safe to keep a 
“ saturated ” solution of “ hypo ” in water, stirring the 
solution before pouring it out into the dish, and adding 
a small proportion of water. Provided the fixation is 
complete, and that the film does not suffer from over¬ 
concentration of the solution, the exact strength does 
not much matter. But the solution must not be too 
weak, nor at all acid. (Note .—Fixing baths made 
deliberately acid have been recommended by good 
authorities, but they entail extra -trouble without extra 
advantages, so far as we can discover.) A freshly-made 
hypo solution is apt to damage the film, under certain 
conditions; the chief reason being the degree of cold 
produced at the time of solution. If the hypo bath is 
found acid, any alkali may be added till the bath is 
slightly alkaline. 
Soon after the plate is put into the fixing solution the 
grey, unreduced silver bromide will disappear from the 
film ; when it has disappeared the plate may, for safety, 
be taken as half-fixed. Many negatives are lost by 
stopping this fixing operation too soon. When the 
plate is fixed, daylight may be admitted. It is necessary 
to remove thoroughly from the film every trace of hypo, 
