18 PHOTOGRAPHIC FACTS AND FORMULAS 
should be about 60° C. (140° F.), and the dye added, prefer- 
ably, in solution. The glass should be levelled, the necessary 
quantity of the dyed gelatine coated on it, allowed to set and 
dried. Yellow screens, suitable for bromide papers and 
lantern slide work: 
- Tartrazine 8g 62 er. 
Gelatine solution, 8% 1000 ccm 16 oz. 
Allow 7 to 10 ccm to 100-qcem, or 750 to 1000 minims per 
100 sq. in. Two such glasses should be bound up together. 
Orange: 
Rose Bengal 3g 23 er. 
Gelatine solution, 8% 1000 ccm 16 oz. 
Use the same quantity as above, and bind one of these red 
screens with one of the yellow tartrazine ones. 
Bright red: 
Xylene red 8g 62 gr. 
Gelatine solution, 8% 1000 ccm 16 oz. 
Use the same quantity and bind with one of the tartrazine 
screens. 
Deeper red: 
Crystal violet, 4% sol. 8 ccm 62 min. 
Gelatine, 8% 1000 ccm 16 oz. 
Use as above with a tartrazine screen. 
Bright red (Hubl): 
Fast red 5g | 384 er. 
Tartrazine 5¢g 3814 gr. 
Gelatine, 8% sol. 1000 ccm 16 oz. 
Allow 7 ccm per 100 qcm, or 750 minims per 100 sq. in. 
This cuts out all light to 600, and is safe for all ordinary 
plates. ; 
Deep red (Hubl): 
Crystal violet 1.65 g 12.7 er 
Cupric sulphate a. 25g 63 gr. 
