The doretype—a de luxe style of portrait photograph

1918 Journal of the Franklin Institute  
THE effect o,f hydrogen on the electrical resis,fivity of' carbon has been studied at different temperatures and pressures. It has been found : i. That hydrogen appaxently produces no effect on the resistivity at ordinary tempe:ratures for pressures up, to 33 atmospheres. 2. That the resistance of carbon increases considerably when the filament is heated to, a high temperature in hydrogen. 3. That the resistance at roo.m~ temperatures following such a heating in hydrogen sho~ws a similar and
more » ... ws a similar and more marked increase. 4. That stlbsequent heating of the filament in vacuum to the same ,temperature produces the opposite effects. 5: That the effect is greater for the higher pressures than for the lower pressures. 6. That these changes are suggestive of an exponential law and are about equal in magnitude in cases where the filaments are not injured appreciably by the processes involved. The Doretype~a De Luxe Style of Portrait Photograph. AlbiON, (The British Journal of Photography vol. 65, No. 3009, p. 4, January 4, I918.) ---A new style o,f portrait photograph, the Doretype, has recently been introduced through the Eastman School Of Professional Photography, as a means of providing a form of portrait photograph of rich distinctive appearance, yet capable of being produced at a comparatively low cost. The Doretype is a warm-toned~ thin, positive image on glass, and receives its brilti~ncy from the' material which is used as a backing. It lends itself to almost any treatment. It may be backed with light-tinted papers, or various. shades of fine silk or satin, but the most satisfactory method is to, coat the back of the transparency with a fine gold bronze. With edges simply bound or the picture mounted in a frame,. most of the attractiveness of the Doretype is lost. The aim of the promoters has evidently been to originate something which in its way can be prized by the possessor just as the dag.nerreotype miniatures were prized in their day. The new process Is not one that can be entrusted to an indifferently skilled operative, but calls for a high degree of skill in the making of the glass transparency, and, like the daguerreotype, needs a fitting setting to show it to the best advantage,
doi:10.1016/s0016-0032(18)90523-5 fatcat:npxddl4dofcjdjy7zc7tt5miky