New Bedford, Massachusetts; its history, industries, institutions and attractions . cription of this process can-not fail to be interesting. In commencing, we have a sheet of thick plate glass which isdesigned for a printing block. The glass is cleansed and is then readyto receive the preliminary coating, which is a solution prepared ofsoluble glass, the white of eggs, and water. The mixture is appliedto the glass as evenly as possible and the film dried and then rinsedwith water. The second stage of the process is the application of afilm of bichromated gelatine to the plate, after which the
New Bedford, Massachusetts; its history, industries, institutions and attractions . cription of this process can-not fail to be interesting. In commencing, we have a sheet of thick plate glass which isdesigned for a printing block. The glass is cleansed and is then readyto receive the preliminary coating, which is a solution prepared ofsoluble glass, the white of eggs, and water. The mixture is appliedto the glass as evenly as possible and the film dried and then rinsedwith water. The second stage of the process is the application of afilm of bichromated gelatine to the plate, after which the glass isput into the drying chamber. The object to be attained is a finegrain throughout the surface of the gelatine, and unless this surfaceis satisfactory, the printing block will never be. If the gelatine istoo thick, the grain will be coarse ; or if the temperature in dryingis too high, there will be no grain. The drying is completed in halfan hour, when the film is ready for printing under a negative, and thisis done in an ordinary printing frame. The exposure is very rapid. N. P. HAYES HARDWARE STORE, INDUSTRIAL AND FINANCIAL. 20I and here the judgment of the photographer is brought into impression is taken from the pressure frame and put into coldwater, where it remains a half hour or more, until the soluble bichro-mate is washed out. Then judgment is passed and the experiencedeye can tell at once wdiat it is fit for. The washed and dried plateshould appear like a design of ground and polished glass. A vellowtint means that it will take up too much ink when the roller is passedover it. The appearance of ground glass is given by the grain. Ifthere are pure lights (almost transparent) and opalescent shadows,the plate is a good one. After moistening in glycerine and water the printing block isready for the press. The inking and printing are done very much asin lithography. To appreciate how skillful a printer must be it is onlynecessary to see the imperfect proofs
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Keywords: ., bookcentury1800, bookdecade1880, bookidbedfordmassa, bookyear1889
