The age-herald., 1901-05-05
eeIatine in the Development.


 When learning Latin roots in my boy hood I remember in one lesson I came to the root 'Jeiu," with the definition frost ice. snow. and one of the examples was gelatine, and thought surely there must be mistake When one looks at a sheet of gelatine the derivation seems very obscure; but put the sheet of gel atine into water and its action under various temperatures shows that some thing of the true character of the stuff Is indicated in the etomology of the word.
 Each particle of bromide of silver which is on dry plate is wrapped in an envel- ope of gelatine. If the reader will remem- Der that this stuff was once sufficiently fluid to be flowed on the plate it will not be so hard to remember that 1t can also be made as fluid by heat and water and will run off the plate again unless care is exercised to keep it from doing so. That Is the first consideration and con- clusion
 The next consideration is what infiu- ence the gelatine envelope has on the particle of bromide of silver in develop ment.
 It will readily be observed that the low CT the temperature the closer the envel- ope clings to the sensitive particle and the harder 1t Is for the solutions to get at it; therefore we use warm water in winter to make the temperature up to about 70 degrees Fah. in the envelope. But in summer when the water Is 80 de- grees and the air 90 degrees the temper ature must be lowered or the gelatine hardened To do the latter Is very diff ficult, scarcely practical, but ice will give the proper temperature and when the plate 10 developed we can then harden as much as we please.
 It will be observed that plate can be developed at a point where the film will not run off, but considerably higher than 70 degrees; the result of this Is that the gelatine envelope Is so soft that the chem icals in the developer get at the sensi- tive material too readily, with the result that the development cannot be stopped so exactly at the right time as If 1t was working more slowly. Then again the gradations are not as fine those who re- member my last article on the revolution in A dry plate will recall the discontent which Is set up in particles adjacent to particles of free silver; when the tenn perature is too high the reduction goes on too rapidly with the result Of loss or detail in the highiights; in other words you get broad patches of pure white where detail should exist
 But when the plate has been developed 1t is desirable to harden the gelatine as rapidly as possible. The gelatine has already been tanned to some extent by the developer. and some proceed to put the plate into an alum bath to harden it. have never had any success with this method as I got markings on my plates at times. A freshly prepared solu- ton of hypo 1 in of water is the best for the amateur. The dissoiving of the hypo reduces the temperature ana the freshly dissolved hypo seems to have a tanning effect.
 There are many formulas for the prepa- ration of acid fixing baths, but while they are all good there is no plan 90 good for the amateur who develops occasionally as the freshly dissolved hypo.
 In extremely hot weather. such as we will have shortly, an additional hardener is necessary. Formaldihydi and water is a good final hardener, but 1t Is very