BUY IT OR MIX IT?
D. WARD PEASE
Amateur Photographer, Chicago, III.
Whether or not you prepare your own photographic formulas, you'll enjoy this discussion of darkroom economics. The author knows both sides of the story, and has reduced the matter down to fractions of a cent.
RECENTLY I was checking up on the cost of preparing a batch of developer according to a formula in which I had become intensely interested. This same formula was available in package form, and I wanted to find out whether I could save enough by mixing it myself to justify the additional trouble involved.
It occurred to me when I finished my computations that the method which I used might be interesting to others who are faced with the same problem. It is now possible to buy in package form practically all of the more commonly used developer formulas for both films and papers. This raises the question of whether it is worth while to spend the money for the accurate scales and other equipment needed for mixing your own materials.
It is necessary to look first into the matter of the purchase of the chemicals required for any given developer formula. The larger the quantity purchased at one time, the less the material will cost. An example is a well-known developing agent which costs 32 cents per ounce. A pound costs $2.67, while sixteen of the 1-ounce bottles would cost $5.12, or nearly double. The best package size in each case would have to be determined by the individual, taking into consideration the keeping properties of the material and the space available for storage, as well as the matter of economy.
The calculation of the cost of materials entering into the making up of a formula depends upon the quantity bought at any one time, or the “purchase unit” as I will call it for convenience. My own idea of a convenient and economical purchase unit varies from time to time, but those given in Table I will serve for the purpose of the present discussion. The prices
shown are the same in several recent catalogs and seem to be standard.
The potassium bromide may seem to be out of proportion for straight developer formulas as given, but it keeps indefinitely, and is very handy to have on hand to make up 10% solutions for addition to diluted paper developers. It is probably possible to buy borax at the grocery for less than the price shown. Some of the other chemicals are available in various degrees of purity at various prices; but the list shown will serve for the original purpose of this article, which is not to quote prices on chemicals.
In making up a formula it is possible to weigh out chemicals according to either the avoirdupois or metric systems. Why any person in his right mind would use the former is more than I can understand. In actual practice, particularly if you are converting to a larger or smaller quantity than the given formula, there is no comparison between the two in convenience. All of the standard formulas
are published in both systems. For the purpose of this article it is sufficient to know that there are 28.35 grams in an ounce and 453.6 grams in a pound. These figures are used in converting the purchase units to metric as shown in Table I for convenience in working out Table II.
The actual method for calculating the cost of the chemicals required to make up any given formula is best shown and worked out in tabular form in Table II, using the well-known D-72 developer as an example.
Water was considered free in working out the above formula. If you buy distilled water, it can be worked into the calculation in the same way as the other chemicals. How are the above figures arrived at? The columns marked “Purchase Unit” and “Cost per Unit” are the same as in Table I and the values under those headings are from that table. To understand the other two columns, the Elon in the above formula can be taken as an example. The purchase unit of one ounce amounts to 28.35 grams. This, divided by 3.1 grams, the amount of Elon in 1 quart of D-72 stock solution, gives 9.14, the number of times this formula can be made up from that supply of Elon. Dividing the cost per unit by the number of formulas to be obtained from one purchase unit gives the cost of that ingredient in the formula. Thus, 0.43 divided by 9.14 equals 0.047.
For all practical purposes we can consider that one liter and one quart are the same. (One liter equals 1.057 quarts if you want to be exact.) For 25 cents you can buy a can of dry chemicals which enable you to make up a quart of D-72 with very little trouble. As shown above, you can save 9V2 cents of this by weighing and mixing the ingredients yourself. Charge that much money saved against the extra time it takes; and you can figure that you are selling your time for extremely low wages, if you want to look at it that way. On the other hand, there is a lot of pleasure and satisfaction in mixing up your own.
The amount of processing work you do has a bearing on the question also. The semi-occasional worker, if he stops to figure it out, will probably find that the economy of the mix-it-yourself method would have to be spread over several years to pay for the scales. And for the apartment-dwelling kitchen or bathroom worker, the actual space taken up by
(Continued on page 76)
(Continued from page 38)
scales and a stock of chemicals is an item.
There is no point in working out on the blackboard before the class the complete figures for each and every formula sold in prepared form. It should be sufficient to give the final results, using the units and prices of Table I, and the methods employed in Table II. These results are incorporated in Table III. This table is based on the assumption that the quart and the liter use the same amount of dry chemical, also that tap water is used and no cost is assigned to it. If distilled water is used at all it should be used in either case, and the additional cost would be the same either way.
All of the developers listed are available in one-gallon size cans, but the mixit-yourself figures would be off due to the fact that anyone making developer in gallon lots would buy chemicals in larger purchase units. With these figures before you, or with figures you can make up yourself for any developer not listed, you can decide whether you are going to mix your own from the bulk chemicals or follow the simpler procedure of buying it in the can. In either case, some further suggestions are in order.
No matter how you mix it, you must have certain items of equipment. Camera stores sell enamel-ware pitchers, but list them only in sizes up to one liter or one quart. A stirring rod is a convenience. A thermometer you have anyway. Suitable bottles will get more attention later in the discussion.
If you want to mix it yourself, a few items are necessary in addition to the above (which will suffice for packaged formulas). First of all comes a suitable balance for weighing out the dry chemicals. The stock of chemicals has been discussed under the matter of the purchase unit.
A collection of formulas to work from is also necessary. This is something like a cook-book in a well run kitchen. And kitchen routine also provides us with another useful idea, in'the form of little file boxes for 3" x 5" file cards with indexes for different kinds of recipes. You turn
the index cards over and write “Film Developers” on the back side of the “Cake Recipes” card, “Reducers” on the back of “Reducing Diets,” etc. Some of the boxes have clips to hold the proper card in view while you mix your batter or developer, as the case may be.
While we are talking about the kitchen it would be a good time to say something about cleanliness. Keep all of the mixing vessels, bottles, scale pans, etc., as clean as you like to see the cooking utensils, plates, and silverware and you are going to avoid a lot of “indigestion” in your photographic operations. And you should avoid having dry chemicals floating around in the air, pyro and hypo being bad actors in this respect. In preparing a developer from a can, all that is necessary is to follow the directions printed on the can. Unless you are sure that your finger is a more accurate means of measuring temperature, you had better use a thermometer to make sure the water is at the desired temperature before starting. When the directions say that one part should be dissolved completely before the next is added, it means just that. In making up a solution with the scales and a formula card, the same fundamental instructions apply. Get the temperature of your water right according to the thermometer, add the chemicals in the same order in which they appear in the formula (unless specifically directed to do otherwise), and be sure that each is dissolved before adding the next.
With some particular types of formulas there are permissible short cuts. Amidol is an excellent paper developer which gets along without carbonate or any other alkali, and does not seem to be at all particular about the amount of sulphite present or the concentration in water. The result is that amidol developer formulas (which do not keep and must be made up as needed) can quickly be prepared by measuring the dry chemicals by volume with the aid of kitchen measuring spoons.
Since we are in the kitchen again, we might as well use the measuring cup too. It works nicely with hypo, since that chemical is used in such large quantities that the usual scales are slow. If you once weigh the contents of a measuring cup of the particular grade of hypo you use it will be much quicker to prepare fixing baths thereafter, as the proportions required will be obtained accurately enough with the measuring cup. Potassium bromide is frequently measured out in very small quantities by making up a solution of 1 ounce of the bromide in 10 ounces of water. Then each ounce of the solution contains Mo ounce of bromide. Any other amount can be measured out the same way with adequate accuracy.
About all that remains to discuss now is how to keep the stuff until you need it. Most developers fall in one or the other of two classes. One class is the stock solution from which a portion is with-
(Continued on page 78)
drawn, diluted for use, and thrown away after one usage. Such stock solutions are better stored in several small bottles rather than one large one. This is so that each bottle will remain only partly filled for as short a time as possible. The ideal way is to have each bottle contain just one portion for each use, but this is not necessary.
The other class of developers are ready for use as prepared and without dilution. Such developers are generally for repeated use. They must be protected from oxidation between usings. If they are left in a deep tank, the common method is. to use a floating lid. Since he is using smaller quantities, the average amateur will pour the solution back into a bottle for storage. The bottle can be kept full as the developer is lost, either by replenishment or with the aid of some glass marbles.
Most developers which are used repeatedly over long periods of time should be filtered or strained occasionally. I have found it convenient to strain them as they are returned to the bottles after each using. With a developer of this type it is necessary to overcome a tendency to want to use the stuff indefinitely. The quality of the negative produced is likely to suffer if this is done. Whether you mix it yourself, or buy it in prepared form in a can, there is no justification in letting the results suffer just to save a few cents.
There is the story. It's possible to do work of the very highest quality using the paper and film developers which come in prepared form. You’ll pqy more this way, but you’ll find preparation simpler and standardization easier to attain. On the other hand, you may be the sort who will not be satisfied until you’ve tried making all possible formulas and variations thereof. And for quantity production the mix-it-yourself system is economical, while it requires a little more equipment and much more time and patience. Figure it out according to your own position and the figures given herewith, then go to work.— fes
New Weston Ratings
O ECENT changes in film speed ratings are announced by Weston Electrical Instrument Corp. They are as follows:
Daylight Tungsten 10.K. Super-XX Cut film.... SO -10 10.K. Panatomic-X Cut film . . 32 12
These new values become official on publication of the next regular issue of the Weston film speed sheet.
Testing Your Lens
PERHAPS you have often wished for some simple test of the quality of your lens. Here is one which requires nothing more than a load of film and a clear night. Take the camera out into the dark and lay it where it will point to the zenith. With the lens wide open and focused for infinity, expose the film for about half an hour. What you are really doing here i> taking star-trail pictures. Upon development the film will be covered with fine sharp lines, each
being the trail of some particular star.
After drying the negative, a careful inspection of it with a good magnifier will reveal much of interest about the lens. First look at the center of the field. The lines should be sharp and evenly black. If they are broad but still evenly black, the infinity focus on your camera is not correct. If the trails look like sharp lines bordered by a slight fuzziness, the lens has spherical aberration. After this preliminary inspection, the trails in the corners of the field should be compared with those in the center. If they differ but little, you may be sure that the lens is satisfactory in all respects. Increasing fuzziness toward the edge of the negative generally indicates curvature of the field. If the fuzziness tends to have a distinctly radial character, there is evidence of coma. And last but not least, a careful inspection of the density of the sky background from center to edge will give an idea of the way the lens illuminates the various regions of the film. Most lenses transmit much more light axially than at an angle to the axis. This will be evident to some degree in your negative.—William Blitzstein, Philadelphia, Pa.