The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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to white light, or there is an action set up which only becomes visible in gold toning. When the Ordinary baths, acetate, borax, etc., were strengthened so as to have the strength of i£ grs. of gold to the 8 oz., instead of I gr., there was less chance of pinki-ness. With the matt papers as well as the glossy, no bath works so well as the plain sulphocyanide, but it is absolutely necessary to get rid of all free nitrate and acid by salt and washing, or else the action was uncertain. Plain paper with uranium and gold toning was a great favourite for black tones, but with the matt-gelatine papers black tones could not be obtained; from this bath we were led on to the others. Now, as to the making of the bath, I always keep my gold in a slightly acid solution ; and before using it requires neutralising. I strongly recommend also that all commercial gold chlorides should be neutralised, because one well-known brand is very acid. The simplest way to do it is to place a little precipitated chalk or magnesium carbonate into the gold solution ; it requires very little for one grain of gold - about as much as will lie on a threepenny piece; shake well, then add the solution to the sulphocyanide. All the sulphocyanides are deliquescent, and when bought should be immediately dissolved in distilled water and kept of a definite strength ; a convenient one is one in four. The quantity of sulphocyanide compared to the gold varies in many formulae, and may vary, provided it is more than four times the weight of the gold and less than sixty times; sulphocyanides will dissolve gelatine when too strong. A convenient strength is gold chloride I grain, sulphocyanide 30 grains, water 8 ounces. See that your dish is clean. Mix your bath by adding the gold to the sulphocyanide gradually with shaking, not the reverse. Never mind the slight turbidity caused by the chalk or magnesia. Place your well-washed prints in the bath, not too many at a time; this is important. Keep them moving, touching them with clean fingers at one corner only. Do not attempt to be economical of gold ; do not tone more than twelve quarter-, six half-, or three whole-plate prints with one grain of gold ; of course, the number depends a good deal on the style of the print. Finally, keep your toning bath at about 650 F. Carry toning on till on looking through the print you see that all the red has disappeared from the heavy shadows for purple tones, and till the red has gone from the half-tones for browns. When the bath is used throw it away or put it in the