TAKING PICTURES 135 



then placed in the hypo. This may be done in the subdued 

 light of an ordinary room. After fixing, it is washed in water 

 and then hung up to dry. 



DEMONSTRATION 17 



Purpose. To show how to develop films in the kodak film 

 tank. 



Apparatus. Kodak film tank, roll of exposed films. 



Directions. Follow the directions that come with the tank 

 and develop a film before the class. Pupils who have a camera 

 may be invited to bring a film to school and develop it them- 

 selves at such time as can conveniently be arranged. 



Printing. As we have already said, the lights and shadows 

 are reversed in the negative. When a print, or positive, is 

 made from this, we get the lights and shadows in their true 

 relations. The printing paper contains salts of silver, like 

 the negative, only they are not so sensitive to light. This 

 paper is put in contact with the negative and exposed to 

 light. Where shadows are heaviest on the negative, the 

 least light will pass through, and so under this the positive 

 will be light ; while those parts of the negative that are 

 lightest will allow the most light to pass through, and here 

 the positive will be dark. Thus the conditions in the object 

 from which the negative was made are reproduced. 



There are two types of paper, the developing and the print- 

 ing out. In the first type, of which velox is a common 

 example, no image appears till the paper is developed. In 

 the second type, of which solio and blue prints are examples, 

 the images appear during the process of exposure. 



Developing paper. The action and treatment of the de- 

 veloping paper is much like that of the film. The paper is 

 placed in contact with the negative and exposed to some 

 light, such as gas or electricity. The time depends on the 

 kind of paper, the light used, and the distance the paper is 



