STUDIO AND WORKROOM 17 
Liquid green filter: 
Acid green 0.6 g 4.6 er. 
Naphthol green 0.6 ¢g 4.6 ger. 
Partrazine _ hove PMS on. 
Water 1000 ccm 16 oz. 
The water in the above formulas is apt to evaporate, and this 
trouble may be overcome by using glycerine instead. 
Tartrazine 0.05 per cent solution absorbs to wave-length 
510. Potassium bichromate 10 per cent solution absorbs to 
550. The same solution plus 0.1 per cent of fuchsine to 620; 
with 0.2 of fuchsine to 630; with 0.5 per cent fuchsine to 
635 ; with 0.2 per cent acid violet to 645. Tartrazine 0.05 per 
cent solution plus 0.02 per cent methyl violet to 660. Thick- 
ness of liquid in all cases 10 cm. For a green light with a 
liquid thickness of 214 cm, use: 
Blueish acid green 0.625 g 4.8 gr. 
Naphthol green 0.075 g 0.576 gr. 
Tartrazine 0.045 g 0.35 er. 
Water 1000 ccm 16 oz. 
In course of time, the water evaporates from the heat of the 
lamp. This can be obviated by using glycerine as the solvent 
instead of water. 
GLass SAFELIGHTS.—Coloured glasses, or glass coated 
with gelatine stained with dyes, are best for illumination of 
the darkroom. ‘The most satisfactory method of making 
the latter is to add a definite quantity of dye to a given 
quantity of gelatine solution and allow a definite quantity per 
area. Soft gelatine is the most suitable, and either a 6 or 8 
per cent solution should be made. Weigh out the gelatine and 
cover with water, stir for about 5 minutes and pour the 
water off, and repeat this three times; finally, drain off as 
much water as possible, melt the gelatine in a water bath, and 
add enough water to make up to bulk. The temperature 
