322 PRACTICAL MICROSCOPY. 



PHOTOGRAPHIC VARNISH (for negatives], 



Gum benzoin oz. 



Gum sandarac I oz. 



Methylated spirit 12 oz. 



FRENCH POLISH. 



Shellac 3 oz. 



Gum sandarac \ oz. 



Methylated spirit . . I pint. 



French polish is sometimes coloured with gum dragon, &c. 



BRUNSWICK BLACK or BLACK JAPAN. 



Egyptian asphaltum 4 oz. 



Linseed oil 4 oz. 



Boil together for some time, and mix to the required consistency with oil of 

 turpentine. 



CANADA BALSAM VARNISH 

 (For rendering ground glass transparent). 



Take 4 oz. of Canada balsam, and bake in a cool oven till quite brittle when 

 cooled. Dissolve this in 12 oz. of benzol, in which \ oz. of mastic has been 

 previously dissolved. 



BLACK VARNISH (Davies). 



Indiarubber shreds 30 grains. 



Egyptian asphaltum . . . . 4 oz. 



Solvent naphtha (mineral) 10 oz. 



Dissolve the indiarubber in the naphtha, add the asphaltum, using heat if 

 necessary. 



BALSAM AND BENZOL. 



Bake the Canada balsam in a cool oven, and then dissolve to the right con- 

 sistency with benzol. If baked too long the residue will be too brittle ; if too 

 short, it will not dry quickly enough. 



DAMMAR AND BENZOL. 



Gum dammar . . . . I oz. 



Benzol 2 oz. 



MASTIC AND BENZOL. 



Gum mastic 4 oz. 



Benzol 3 oz. 



