A Few Chemistry Tips For The Photographer — Photo Beacon magazine, March 1899
Reading through a Photo-Beacon magazine circa 1899, it's interesting to learn about the common mistakes and the best practices of the time for darkroom chemicals. Certain concerns, issues such as contamination and mixing chemicals, seem to be more or less the same even today for the slim minority of photographers who process film and prints at home. Enjoy!
A FEW CHEMISTRY TIPS FOR THE PHOTOGRAPHER
It is amazing to see what a large number of amateurs manage to struggle on with absolutely no knowledge of chemistry or the theory of photography, although I hope a good many have mastered the principles of the latter by means of the excellent articles which appeared a short time ago in the Amateur Photographer from the pen of W. Ethelbert Henry, C.E. I am sure amateurs would find things work more smoothly, and their results would be much more certain, if they would only learn a little of the mysteries of chemistry. There are several little stumbling blocks which chemistry puts in the path of the unwary photographer, and it is the object of this article to point out some of these.
First, let us look at the theory of "crystallization." Suppose we have a solution of a chemical, and wish to get that salt back again into its solid state, how should we go to work? If we are in a hurry, we should gently heat the solution over a spirit lamp or gas burner, and so drive off the water and leave the salt behind; but if time is of no consequence, then stand the dish of solution in a draft of warm, dry air for a day or two, and you will find the water will evaporate off and leave the salt behind, but in larger crystals than in the first case. Now take some of these crystals and thoroughly dry them on blotting paper, and then transfer them to an evaporating dish, or, failing that, an old saucer, and gently heat them. They will crackle and melt, water will be driven off, and the salt will remain as a powder. Now where did this water come from? It was actually combined in the crystal, and was, in this particular instance, necessary to enable the salt to assume a crystalline form. Without that water, as we have seen, the salt remains as a powder.
Now let us see how this little secret of Mother Nature affects the unwary photographer. He is told to make up a solution of copper sulphate. The formula says: Copper sulphate 1 ounce, water to make 2 ounces. He utterly ignores the words "to make," and at once gets an ounce of copper sulphate, measures out two ounces of water, and dissolves the sulphate in it. Now let him measure the volume his solution, and he will be astonished to find that it is several drams over the two ounces, but where the extra water came from he is quite at a loss to say. He is fairly in a muddle now, for his solution is weaker than it ought to be, and consequently his results will be very uncertain. Now all this trouble is caused by the "water of crystallization.” He was not aware that when he dropped the ounce of sulphate into the water he was also adding more water. Those two words "to make" are put in to allow for that. The correct way to have made up the solution would have been to put 1 ounce of sulphate into a 2-ounce measure, add about an ounce of water, and then, after the salt has all dissolved, make the volume of the solution up to two ounces.
Another little bit of chemistry which every photographer should know is the great affinity which sulphuric acid has for water. Many an accident has occurred in chemical laboratories through students forgetting this. The unwary photographer sees a formula in which, among other things, are sulphuric acid and water. Quite naturally he starts by mixing the liquids first, and, measuring out the water, he adds the requisite amount of acid. The next thing that happens is that hardly has the acid touched the water before a snap is heard, and there is a clean crack right round the vessel, just at the surface of the water. Why is this? It is simply because when sulphuric acid is mixed with water some kind of action is started which produces great heat, the result being that the glass is cracked. When mixing the acid with water, it should be added drop by drop, and carefully stirred.
There are certain chemicals — for instance, ferrous sulphate, pyrogallic acid, and sulphite of soda — which have a great tendency, when exposed to the air, to change into something else, and therefore, when both in the solid form or in solution, they should be kept from the air as much as possible, either by seal in the bottle down, or, if in solution, the surface of the liquid can be covered with a layer of castor or some other oil.
Suppose a chemist has a bottle of solution in his right hand, and in the other a bottle or measuring glass, which he wants to hold up against the light while filling. How does he remove the stopper and hold it while pouring out the solution? The beginner would naturally take out the stopper and lay it on the bench, but the chemist knows that it is there liable to pick up all manner of contaminating things, and he prefers to keep it in his hand. He stands the bottle on the bench, and, turning the back of his hand toward the stopper, grips it between the first and second fingers. Now, after taking out the stopper, he can turn his hand the right way round and lift the bottle in the ordinary way, while the stopper will be sticking out from the back of his hand.
It is often very aggravating to have to wait, say, half an hour, while a solution is filtering, for often in the old style of folding the papers it took quite half an hour to filter a fair quantity. The object which should be sought is to get as large a surface of paper exposed as possible, and therefore I believe you will find it better to follow out this method of folding your paper: Take a filter paper, or a clean circular piece of white blotting paper, and fold it in halves. Then fold again and again, always letting the fold go through the center of the original circle, and continue this till you have a segment-shaped piece about a quarter of an inch across. Now open this out, and, putting it into the funnel, manipulate it so that there are a number of "pleats " (in dressmaking parlance) all round. This, you will find, will filter a solution a good deal faster than a paper folded into the old-fashion quarters.
Finally, every chemist knows what a hash a slovenly worker will make of anything he undertakes in that science, and this also applies to photography. Therefore, let me urge upon all amateurs to be as neat as possible, and not to leave apparatus lying about dirty any longer than is absolutely necessary.
A. A. M.
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