3O THE A B C OF PHOTO - MICROGRAPHY 



densed upon its sides or top. If these pre- 

 cautions are taken you will never have any 

 smell or trouble with the use of oil in the 

 dark-room lamp. 



The trays for developing may be of hard 

 rubber (preferably), celluloid or agate-ware. 

 Do not touch papier mache. It looks very 

 nicely at first, but the sharp edges of glass 

 plates soon cut through the varnish or enamel, 

 and then the life of the tray is but brief. 

 Porcelain is easily broken and heavy. Hard 

 rubber is altogether the best. There should 

 be at least three graduates, 2-oz., 4-oz. and 

 8-oz. For the fixing bath I find on the whole 

 a hard rubber or agate-ware tray of 8 x 10 

 size, fitted with cover, to be the most satisfac- 

 tory. The acid fixing bath (formula for com- 

 pounding which is given with most makes of 

 plates) is undoubtedly the best, keeping clear 

 and clean until exhausted. My own formula, 

 as below, is recommended : 



Sodae hyposulphite 16 ozs. 



Sodae sulphite 4 ozs. 



Chrome alum i oz. 



Sulphuric acid I drachm. 



Water 64 ozs. 



As the alum dissolves very slowly, it should 

 be powdered in a mortar, or a portion of the 



