Lecture by Mr. D. Mennie before the Shanghai Amateur Photographic Society on Friday, the 15th of December.
The toning of bromide and gaslight papers is a subject to which it seems that little or no attention has been given the members of. our Society. This. instanced by the large preponderance of black and white pictures shown at our last exhibition. With the exception of a few prints on carbon, the great majority of pictures were printed on bromide, or gaslight papers and the exhibition suffer-to a certain extent, from the monotony of black and white prints.
The rendering of Black and white given by'an ordinarily developed bromide print is not suitable. or "pleasing for all subjects. In order to give more scope to it 'the "bromide thods posed." Most of the methods are.-both easy and simple to carry out and: with the exception. of iron toning, yield " results the permanence of whioh no four neil be felt.
The following are the methods which. I shall endeavour +o deménstrato this ovening The obtaining of sepia tones by sulphur toning.
Phe copper ferricyanide process giving purple brown and red tones.
Blue and green tones by a solution of ferric fercieyantde and uranium, There are two methods of obtaining sepia tones on bromide paper, Immorsing the print la a hot hypo and alum bath for a time varying from 10-30 minutes will: yield sepia tones. - If the bath is used at ordinary athos temperature prints may take as Jong as three days to tone, The best result can ly be obtained. by using a bath which is neither too fresh, nor too old, and this somewhat difficult to determine. 'The hypo-alum method is now almost discer ed in favour of a much simpler proce by which splendid dark, brown tones be obtained easily and readily, This process consists "in bleaching. the' print tither fae solution 6f potass érslogtalde or iodine and then immersing in sodium sulphide (not, sulphite) solution till the equisite sepia colour is obtained. This is known hnrotting the silver image by which the silver image is converted ito sulphide of silver.
One grout advantage possessed by this method of touing is that, silver. sulphide being about, as permanent a compound, sulphur-toued. prints, may be regarded as having better lastin, properties then an ordinary untoned bromide print. Another important point process is that prints suffer no change in detail or gradation, The simplest blenching agent is a solution of potassium, ferricyanide and bro-um, Prints are immersed peared. This takes place in loss than a minute. When bleached, wash in three or four changes of water and transfer to a solution of sodium, sulphide—} oz. to 25 oz. of..water,—until original: detail appears which takes about 15 seconds, If prints are developed longer than a minute blisters may appear. Final washing in water for half-an-hone complotes the process.
Priuta to be toned by the above proc should be fully developed; over-expo or under-developed prints do not give 40 good a colour.
With regard to copper' toning, the range of tones obtained by this process 18 very wide. The cold black silver image gradually changes to warm black, then a dark brown, and -aftorwards, through various sha: ie3 of brown: to bright. red, The print is. taken out of the toning bath when the desired colour is obtained and afterwards washed in running water for 20 minutes.
'The best tones obtained during' the copper-toning process are those which occur at the bugitming and-end of the process. A rusty-looking, or greenish bromide print can be changed ina minute oF less to a pleasing warm black. Fine red, chalk tones are obtuived. by immersing the print for a period varying from ten to twenty minut Blue tones are very 61 ied by immersing prints ina bath composed of potass, ferridya i iron, nitric acid, and water. takes place in loss than 9 minute, Afver
Text read from the printed page and cleaned; old type leaves the occasional error.