CHOICE OF PAPER, ETC.] UNDULATORT FORCES. LIGHT PHOTOGRAPHY. 



153 



In our earlier pages we gave some elementary ex- 

 periments, illustrating the process of paper-printing. 

 They were, however, necessarily of rather a crude cha- 

 racter, because they were only intended as an introduc- 

 tion to photographic practice. We must now enter 

 more fully into the minutiae of the process, and so 

 assist the operator in overcoming many difficulties which 

 arise in its pursuit. We shall, therefore, examine each 

 point in detail, so that the successive steps may be fully 

 understood by all our readers. For this purpose, it will 

 be proper that we should divide the process into separate 

 heads ; and in its pursuits, we must remind our readers 

 of the necessity of care and complete cleanliness, as of 

 the last importance. The following are the different 

 points to which we shall separately call the attention of 

 the experimenter : 



1. The choice of paper. 



2. Its preparation. 



3. The copying process. 



4. The fixing. 



5. The toning. 



1. The Choice of the Paper. Perhaps this is the most 

 difficult, because it is the most uncertain, part of the 

 whole affair. However much care is exercised in the 

 selection, still gome hidden defect is mire to appear in 

 almost every specimen when it is submitted to the pho- 

 tographic process. At the present time, however, there 

 are gome paper manufacturers who produce an article 

 intended solely for photographic use; and this, to a 

 considerable extent, modifies the difficulties with which 

 the photographer will have to contend. This is sold 

 under different names, according to that of its maker. 

 There U, however, a general title of French and English 

 prepared paper. Either may be obtained, ready salted 

 and albumenised, of the photographic chemist ; and we 

 shall, therefore, dismiss them without further remark, 

 and devote some space for the benefit of those who may 

 be unable easily to procure them. We may observe, that 

 the two kinds of paper most esteemed by photographers, 

 are the 8<ixe paper and the papier Rive. 



In the manufacture of all sorts of writing-paper, nu- 

 merous impurities, in a photographic point of view, are 

 always present. The water employed in washing the 

 rags, in reducing them to pulp, and in subsequent 

 processes, contain common salt, sulphates, A-c. ; and in 

 two cases within our knowledge, an appreciable amount 

 of lead, or its sulphide, hag been detected, owing to the 

 impregnation of the water by that metal as it flows past 

 the mines. Oxide of iron is almost invariably present, 

 and no doubt exercises a decided effect on the results 

 obtained in paper. We do not wish to multiply the 

 difficulties which present themselves to the tyro ; on the 

 contrary, we prefer that he should know the chances of 

 failure which may continually present themselves ; and, 

 by being forewarned, he may, by patience and care, be 

 equally forearmed. 



During the manufacture of paper, a portion of size or 

 tarch, and occasionally both, are introduced, for the 

 ]>iir|><i8e of giving a smoothness and evenness of surface 

 to the texture. Our readers will be prepared to find that 

 uch matters have a decided effect on the nitrate of 

 diver, which is the salt usually employed to sensitise the 

 paper. A drop of the solution of that salt immediately 

 produces a black spot on the hands, owing to the in- 

 creased or peculiar action which occurs from the presence 

 of animal matter. Generally speaking, animal or vege- 

 table matter is always present in some form during 

 photographic processes; but when so in circumstances 

 beyond our control, it is often a source of great iii- 

 convrnience. 



With respect to ordinary sizing, there is no remedy ; for 



; rig, filtering, or bibulous paper, are all objectionable ; 



and the patent paper parchment which is prepared from 



these by means of sulphuric acid, is, from other causes, as 



unfit for photographic purposes. 



We have found, that the best paper of an ordinary 

 kind, and which is generally to be procured in most 

 place*, U common drawing-paper ; that is, such as U used 

 for Icad-iKiucil drawing. Ail cream and blue-hud oaoer 



VOL. I. 



are utterly useless. The plain Bath or satin post may be 

 employed; subject, however, to the difficulties and 

 objections to which we have already alluded. The 

 points requiring attention are that the surface should be 

 even ; not too highly glazed ; free from spots ; and the 

 paper itself as chemically pure as possible. These results 

 can only be practically arrived at by repeated and careful 

 trials. 



Albumenised paper is generally employed by photo- 

 graphers, because the addition of the animal matter has 

 a very good effect on the appearance of the positive, both 

 during the process and after its completion. The mode 

 of applying this, together with the salting process, we 

 shall presently explain. Gelatine, starch, <fec., are also 

 used for the same purpose; but they are not so con- 

 venient in manipulation, or generally so successful in the 

 result, as the white of an egg, which is nearly pure 

 albumen. 



Before proceeding to describe the preparation of the 

 paper, we may state, that there are a variety of causes 

 which, independent of the manufacturing faults, produce 

 inconvenience to the experimenter. 



In cutting, sorting, and packing writing-paper, <tc., it 

 necessarily passes literally through many hands ; and 

 each time it is fingered, it acquires, in some part, a portion 

 of grease and common salt. Despite, therefore, of all 

 possible care in selecting a good paper, these accidental 

 circumstances tend to spoil it in some parts. Hence, we 

 often find unaccountable spots, and what are called 

 " stars" on the surface ; these being generally brought to 

 light during the fixing process. -For these we can offer 

 no remedy; only let the operator be careful that he 

 does not increase their number by his own carelessness. 



2. The Preparation of the Paper. If our readers can 

 supply themselves with any of the different sorts of paper, 

 ready salted and albumenised, the remarks we are about 

 to make will be superfluous. But we should not be 

 carrying out the general plan of our work, did we not 

 prevent, as far as possible, the chance of our readers 

 being left to their own resources, without any aid w .lich 

 we can afford them. We shall, therefore, give plain 

 directions for the salting and albumenising process, and 

 then deal with the modes adopted for making the paper 

 so prepared sensitive to the action of light. The lattor 

 process is, of course, as equally necessary in its application 

 to paper which may be purchased readily prepared, as 

 for that which may be salted, Arc., by the student at 



llMlIII'. 



The albumenisation and salting of the paper may be 

 thus effected. Break a sufficient number of fresh eggs 

 as to produce two fluid ounces of the white, which must 

 be poured into a clean vessel as it passes out from the 

 shell. Care should be taken not to mix any of the 

 yolks with it. To the clear albumen so obtained add 

 an equal quantity of distilled water, in which has been 

 dissolved eighty grains of chloride of ammonium (sal-am- 

 moniac). This salt U to be preferred to any other, for 

 many reasons, and its action is generally to be depended 

 on. Shake up the albumen and the water together, and 

 when well mixed, pour them into a tall glass jar or 

 bottle, and leave the mixture at rest for several hours. 

 The clear liquid may then be poured into a plate or 

 other flat receptacle, and after adding to it ten drops 

 of liquid ammonia, it is ready for use. Then turn up 

 one corner of a sheet of paper, so as to serve as a kind 

 of handle, and placing the part next to the corner first 

 on the surface of the liquid, gradually draw the whole 

 of the paper so that each portion shall be equally 

 moistened. If this be properly managed there will be 

 no air-bubbles left on the paper surface. It may be 

 left on the liquid for a few minutes, and is then to be 

 hung up to dry in a moderately warm plac. The 

 object to be attained is that of an even coat of the 

 albumen, so that when the paper is dry, each portion 

 shall present a regular and even appearance. A good 

 deal must be left to the tact of the operator : if, how- 

 ever, our instructions are carefully followed, there need 

 be no risk of failure. Any quantity may be so pre- 

 pared ; and if it U properly dried, and kept in a dry 



