1883.] 



MICROSCOPICAL JOURNAL. 



107 



use, and it can be used repeatedly 

 until it ceases to act. 



To intensify a negative it ts thor- 

 oughly washed, so as to remove every 

 trace of hyposulphite. It is then im- 

 merged in the intensifying solution 

 until it acquires sufficient strength, 

 after which it is washed and dried. 



If the solution acts too quickly the 

 strength may be reduced by the addi- 

 tion of water. Some persons prefer 

 to use a very much weaker solution 

 than we have given above. 



2. Silver intensifier. — There are two 

 solutions requisite in this process : — 

 a. Pure ferrous sulphate, 5 grains. 

 Citric acid, 10 grains. 



Water, i ounce. 



^. Silver nitrate, 20 grains. 



Water, i ounce. 



After fixing, the negative should be 

 throughly washed. When this method 

 of intensification is to be followed we 

 prefer to fix the picture in a solution 

 of 30-40 grains of potassium cyanide 

 in 5 ounces of water instead of in the 

 hyposulphite solution. The negative 

 should not be allowed to dry before 

 it is intensified. 



The operation is conducted as 

 follows : The negative is placed in 

 a clean developing pan and flowed 

 with a sufficient quantity of solution a 

 to cover it, having previously added 

 one of two drops of solution d to each 

 ounce of solution a. Keep the solu- 

 tion gently flowing over the plate. In 

 a few moments the picture will begin 

 to increase in density, and as it slowly 

 grows darker and darker the opera- 

 tion can be stopped at any moment by 

 washing in water. It is advisable to 

 mix a fresh solution for each plate, 

 for when the liquid becomes turbid 

 it should be thrown away, , 



Printing. — The next operation to 

 be described is printing. For this 

 purpose a printing-frame is required, 

 which can be obtained from dealers in 

 photographic goods. Prints may be 

 made either on " ferro-prussiate " 

 paper, which gives figures in blue on a 

 white ground, or on the silver paper in 

 general use by photographers. The 



blue prints are so easily and cheaply 

 made that there is much to commend 

 them. They do not compare in deli- 

 cacy with silver prints, but they serve 

 very well for many purposes. Silver 

 prints are more troublesome to pre- 

 pare, and for this reason we have 

 heretofore advised beginners to send 

 their negatives to practical photogra- 

 phers to have them printed. How- 

 ever, as many prefer to do all the 

 work themselves, we will give full in- 

 structions for preparing the solutions 

 and using them. 



Blue Prints. — The ferro-prus- 

 siate paper can be purchased in large 

 sheets ready for use. It can be kept 

 for some time without spoiling, but as 

 it is a very easy matter to prepare the 

 paper, we prefer to make our own. 

 Select a good quality of book paper, 

 not glazed but smooth and well- 

 finished. Cut it in sheets of conven- 

 ient size to be easily coated — 

 about ten inches by twelve is a good 

 size. 



The solution for sensitising the 

 paper is made as follows : 



a Dissolve 35 grains of prussiate 

 of potash in half an ounce of water. 

 l>. Dissolve 51 grains of citrate of iron 

 in half an ounce of water. Mix the 

 two solutions and pour the mixture 

 into a small dish or saucer. 



Select a smooth board, spread a 

 sheet of the paper upon it, and in a 

 room lighted by a lamp or candle 

 brush the surface of the paper with 

 the solution by means of a small piece 

 of sponge or cloth. Only enough of 

 the solution should be applied to coat 

 the paper evenly — not enough to run 

 in streaks when the paper is hung up 

 to dry. When coated, the paper is 

 suspended by one corner, and left to 

 dry in the dark. The sheets will keep 

 for some time, if placed in a dry place 

 protected from light. 



Place the negative in a printing- 

 frame, then place a piece of the sen- 

 sitized paper in contact with the 

 varnished face of the negative, close 

 the frame and expose the picture to 

 the light. Allow the printing to con- 



