Photomicrographs and Lantern Slides 145 



The solutions keep indefinitely and may be used three or four 

 times. 



Apply the intensifier after fixing in hypo and washing in water. 

 If the negative or slide has been allowed to dry, soak it in water for 

 half an hour before intensifying. 



Place the negative or slide in A, rocking the tray as in developing, 

 until it becomes gray or even white. Wash in water for 1 minute 

 and then transfer to B and leave until the dark color can be seen on 

 the back of the negative or slide. Wash in water as thoroughly as 

 after fixing in hypo. 



Some use a saturated aqueous solution of the bichloride of mer- 

 cury, without the bromide of potassium; and, instead of solution B, 

 use water to which ammonia has been added about 1 part ammonia 

 to 40 parts water. Excellent sepia tones may be secured in this 

 way. Wash well in water. 



After the plate has been thoroughly washed in water, wipe it 

 gently with a tuft of cotton. The cotton must, of course, be thor- 

 oughly wet; it is better to hold the plate under a stream of water 

 while wiping. This should always be done before placing a negative or 

 slide in the rack to dry, after a washing in water. 



Toning Lantern Slides. A lantern slide may sometimes be made 

 more effective by judicious toning. The hints given here merely 

 introduce the student to the possibilities of the subject. 



Light Sepia to Red Tones. Overexpose up to four or five times 

 the length of exposure for a normal slide in black and white; develop 

 thoroughly; fix and wash as usual; then tone in the following 

 solution : 



Metric Apothecaries 



A. Potassium ferricyanide 6 g. ( 90 gr.) 



Water 295 c.c. ( 10 oz.) 



B. Copper sulphate 7 g. ( 110 gr.) 



Potassium citrate 65 g. (1,000 gr.) 



Water 295 c.c. ( 10 oz.) 



(The metric and U.S. measures are practically rather than arithmetically equivalent.) 



When needed for use, pour some of A into an equal quantity of 

 B, stirring or shaking constantly. Put the slide into the solution in a 

 tray and rock just as if developing a plate. The solution is a strong 



