13 



lights, and the shades by shades, may be taken in the manner 

 described under the next head. 



Mr. Fox Talbot has recently published a method of removing 

 the yellowish tint from pictures taken on calotype and other 

 photographic papers prepared by nitrate of silver, by plunging 

 the picture into a bath composed of hyposulphite of soda, dis- 

 solved in ten times its weight of water, and heated nearly to the 

 boiling point. The picture should remain in it about ten minutes, 

 and be then washed in warm water and dried. By this means, 

 he says, the picture is rendered more permanent, and the lights 

 whiter. He also recommends the following means for improving 

 photographic pictures : 



" A copy or reversed impression of a photographic picture is 

 taken in the ordinary manner, except that it remains in the light 

 twice the usual time ; its shadows are thus rendered too black, 

 and its lights not sufficiently white. It is then washed and 

 plunged into a bath of iodide of potassium (of the strength of five 

 hundred grains to each pint of water) for one or two minutes, 

 which makes the picture brighter, and its lights assume a pale 

 yellow tint. After this it is washed, and immersed in a hot bath 

 of hyposulphite of soda, until the pale yellow tint is removed, and 

 the lights remain quite white. The pictures, thus finished, have 

 a pleasing and peculiar effect of light and shade, which is not 

 easily attainable by other means." 



The transparency of calotype and other pictures may be in- 

 creased by causing melted wax to penetrate the pores of the paper 

 in the following manner. A small quantity of white wax is 

 scraped on the back of the picture, it is then placed between two 

 other papers, and a hot iron passed over it, which melts and spreads 

 the wax. Or a little boiled oil may be spread over it, and the 

 excess removed by bibulous paper. Canada balsam, or mastic var- 

 nish, with turpentine, are very good materials for the same purpose. 



It may be necessary to remind the reader, that the CALOTYPE 

 is a patented process. In the two patents obtained by Mr. Fox 

 Talbot, the use of the following processes is claimed as his exclu- 

 sive right. Some of these claims must, however, be considered 

 invalid, and would possibly affect the value of the entire patents 

 if brought to trial : 



The employment of gallic acid, or tincture of galls, in conjunc- 

 tion with solutions of silver, to render prepared paper more perfect. 

 The obtaining portraits from life by photographic means upon 



