SCIENCE- G OSSIP. 



CONDUCTED BY B. FOULKES-WINKS, M.R.P.S. 



EXPOSURE TABLE FOR OCTOBER. 



The figures in the following table are worked out for plates of 

 about 100 Hurter & Driffield. For plates of lower speed number 

 give more exposure in proportion. Thus plates of 50 H. & D. 

 would require just double the exposure. In the same way, 

 plates of a higher speed number will require proportionately 

 less exposure. 



Time, 11 a.m. to 1 p.m. 



Between 9 and 11 a.m. and 1 and 3 p.m. double 



the required exposure. Between 8 and 9 a.m. and 



3 and 4 p.m. multiply by 4. 



Subject 



P. 5-6 



F. 8 



F.ll 



F.16 



F.22 



F. 32 



i 



F.45 



1 

 I 



F.64 



Sea and Sky . . 



250 



T*T 



6 1 * 



s\ 



Open Landscape 

 and Shipping 



(A 



1 



32 



1 



l 



* 



I 



1 



2 



Landscape, with 

 dark fore- 

 ground, Street 

 Scenes, and 

 Groups 



1* 



h 



1 



I 



£ 



1 



2 



4 



Portraits in 

 Rooms 



}' 



8 



16 



32 



1 



- 



- 





Light Interiors 



15 



30 



1 



2 



4 



8 



16 



32 



Dark Interiors 



1 



2 



4 



8 



16 



32 



64 



128 1 



The small figures represent seconds, large figures minutes. 

 The exposures are calculated for sunshine. If the weather is 

 cloudy, increase the exposure by half as much again ; if gloomy, 

 double the exposure. 



Chemistry of Chromate Printing. — On page 

 135 in this number will be found an article upon 

 the Chemistry of Chromate Printing with special 

 reference to the Carbon and Ozotype processes. 



Exhibition of the Royal Photographic 

 Society. — By the time this number of Science- 

 Gossip is in the hands of our readers the forty- 

 sixth annual exhibition will have been opened to 

 the public. The opening soiree is to take place on 

 September 28th, at eight o'clock in the evening, 

 when the members will be received by the Pre- 

 sident. The Exhibition, which is to be held in the 

 New Gallery, 121 Regent Street, W., will be open 

 to the public on Monday, September 30th, until 

 Saturday, November 2nd, from 10 a.m. to 6 p.m., 

 and on Monday, Thursday, and Saturday evenings 

 from 7 to 10 p.m. We understand that this year's 

 exhibition will prove to be one of the most suc- 

 cessful on record, both from the point of view of 

 interest and in the number of pictures sent in, and 

 will be of the highest artistic merit. To lovers of 

 the art or science of photography this year's show 

 will be one of exceptional interest and pleasure, 

 and we have no doubt that if photographic friends 

 would induce some of their acquaintances to visit 



the exhibition, the result would be an increase in 

 the ranks of the amateur photographer. Apart 

 from the purely photographic sections, there are 

 plenty of exhibits highly interesting to all classes 

 of science workers, such as astronomical photo- 

 graphy, etc. We also expect to see some very 

 beautiful examples of colour photography by 

 different processes. Judging from the amount of 

 labour and thought that has been expended in 

 this direction since the last exhibition, we feel 

 confident the examples exhibited will show a 

 marked advance since last year. There will be an 

 exhibition of lantern slides on Monday, Thursday, 

 and Saturday evening. These slides are selected 

 from a very large number, and can be taken as 

 fairly representative of the best work in lantern 

 slides of the year. We shall give a full report of 

 the exhibition in our November issue, when we 

 shall also have a reproduction of one of the best 

 pictures in the exhibition. 



Paget Prize-plate Company's New Self- 

 tone Paper. — This company has recently intro- 

 duced a new self -toning printing-out paper, -which 

 is very simple in working, and gives most satis- 

 factory results. The printing process is precisely 

 the same as with ordinary printing-out. paper, ' but 

 the toning and fixing differ, in that the paper 

 requires fixing only. It may be fixed in a weak 

 solution of hyposulphite of soda, and will give a 

 very pleasant rich brown tone. Should it be 

 desired, however, to secure a more purple tone, all 

 that is necessary is to add a little common salt to 

 the fixing solution, the quantity of salt varying 

 according to the tone desired. It is possible by 

 this means to obtain any particular tone or colour. 

 This paper is a collodio-chloride emulsion, and 

 when dry has a kind of semi-enamel surface, which 

 is very hard. We understand the company is pre- 

 paring a similar paper that will have a matt 

 surface. That class of paper will, we feel sure, 

 have a large sale, as the tones produced are most 

 suitable for a matt-surface paper. 



Developing Backed Plates.— We have fre- 

 quently heard complaints with regard to the diffi- 

 culty of developing backed plates without getting 

 any of the backing on to the surface of the film. 

 It is generally recommended that the plate should 

 not be soaked in water before developing, as that, is 

 apt to cause air-bells, and thus leave transparent 

 spots on the developed negative ; therefore soaking 

 should be avoided. Again, it is suggested to wash 

 off the backing before developing. In this method 

 there is great risk of the washing running over the 

 film, and thus causing uneven development. Then 

 it is recommended by some makers to remove the 

 backing by means, of a wet flannel ; but this is 

 a very dangerous process, for the operation, being 

 necessarity carried out in the weak light of a dark- 

 room, it is most difficult to avoid marking the film. 

 The method we have' found most successful is to 

 put the plate into the developer without removing 

 the backing, and, when the picture is just beginning 

 to show, to take the negative out of the developer and 

 hold it under running water, and at the same time 

 rub the backing off the plate by means of a stiff hog- 

 hair brush. We ourselves use an ordinary mounting- 

 brush. By this means the whole of the backing is 

 easily got rid of, and the plate can then be put 

 back into the developer, and development proceeded 

 with in the usual way. 



