•2240 Journal of Applied Microscopy 



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LABORATORY PHOTOGRAPHY. 



L. B. ELLIOTT. 

 Devoted to Methods and Apparatus for Converting an Object into an Illustration. 



A HINT FOR OVER-EXPOSED SLIDES. 



Many people will find that some of their slides are over-exposed. This is 

 seen by the image coming up and at once rapidly darkening. If the slide was now 

 fixed it would be flat and of bad color. Instead, however, of removing the slide 

 from the developer' and fixing, continue developing it until it is very dense and 

 very much over-developed. Then, after fixing, the slide must be placed wet 

 with hypo, into a bath of ferricyanide of potassium. To prepare this bath add 

 a few crystals of the above salt to a dish of water — in fact, enough to make the 

 solution a canary yellow. The slide in this bath rapidly reduces, and the 

 operation must be continued till the density is considerably thinner than a nor- 

 mal slide should be. Wash thoroughly to get rid of hypo., and bleach the slide 

 thoroughly in the following — in fact, it will be impossible to over-bleach it : 

 Mercuric chloride, 50 gr.; potass, bromide, 50 gr.; water, 5 oz. After this, wash 

 well to get rid of the mercuric chloride and blacken with ammonia (.880), 1 oz., 

 water, 20 oz. The slide will now be found to be crisp, with perfect gradation 

 and a very pleasing color. 



This method is particularly useful for getting good slides from very thin 

 negatives, only care must be taken in the first place not to over-expose. For 

 sea-scapes, if the exposure is made so as to get a black tone, and the slide 

 is under-developed, and after fixing and washing well is only intensified, a most 

 intense beautiful purple black will be produced, almost as fine as wet collodion. 

 — Photographic News. 



On Using Bromide. — A bottle of 10 per cent, bromide of potassium should 

 find a place in every careful worker's dark-room, in case of sudden fog appear- 

 ing, or when it is manifest that the exposure has been excessive. A drop or 

 two added to the developer under such circumstances will often save a plate 

 which, under normal circumstances, would find its way to the dustbin. Bromide 

 should not be kept in an ordinary bottle, but should be stored in a " drop bottle," 

 or similar device. A very good substitute, and one which will answer quite as 

 well, if not better, is found in the form of a small bottle having a hole bored in 

 the cork of sufficient size so that a fountain-pen filler can be fitted tightly into 

 it. The filler is allowed to dip to the bottom of the bottle, and any time that a 

 drop or so of bromide is required, it is a very easy matter to compress the 

 India rubber, withdraw the cork and tube from the bottle, and discharge the 

 necessary number of drops. — ^.v. 



