9.7.
PLATE
DEVELOPMENT
313
ufacturers, to inspect each plate before it is placed in the microscope to
be sure it is free of lint and dust. This is done by reflecting light from
the safelight source. When particulate matter is seen, it can be removed
with a fine camel's-hair brush, or it can be blown away with a rubber
bulb or a freon "duster" such as is marketed by E. F. Fullam Inc.,
Schenectady, New York.
9.7. Plate Development
Almost as important as the type of plate used is the manner of its
development if suitably fine grain and good contrast are to be obtained.
In general, it is best to follow the manufacturer's recommendations,
although with some qualification. Manufacturers usually suggest a choice
of developers, one of which may particularly emphasize fine grain, another
contrast, and a third convenience. Since contrast is often the greatest
problem in electron microscopy, the developer which is selected should
feature this. Unfortunately there is inevitably a reciprocal relationship
between contrast and grain size with any particular emulsion. One cannot afford to choose the developer with greatest contrast without making
too great a sacrifice in grain, but even less can one afford to sacrifice
contrast for the finest grain developers. Truly fine grain developers lack
contrast to such a degree that they are well nigh worthless for electron
microscopy. Thus, one should select a developer tending to emphasize
contrast, but with suitably balanced characteristics.
The Kodak Company recommends D-19 as the developer of choice for
most electron microscopy. This was originally formulated for X-ray
work, and later proved desirable for aerial photography. It gives a brilliant, vivid image with less "chemical fog" than most other developers.
FIG. 37. A portion of a mitochondrion from an acinar cell of the parotid gland
of a rat (X 165, 000). (a) A micrograph made on Kodak Lantern Slide Plates, Contrast
Grade and photographically enlarged excessively (X 11) to demonstrate grain size,
(b) The same field photographed on Kodak Spectroscopic Plate, Type V-O. The original
exposure on the latter plate had to be approximately four times that of the other.
There were not, however, significant differences in the contrast values, and here both
prints are on the same grade of enlarging paper. The spectrographs plate has a
decidedly
finer
grain. However, photographic grain ordinarily is not what
limits
resolution, and in this instance the second picture does not reveal more detail than
the first. Pictorial resolution was limited by the character of the specimen, and perhaps
by the performance of the microscope. The tissue was fixed in osmium
tetroxide,
embedded in methacrylate, and was not stained.
PLATE
DEVELOPMENT
313
ufacturers, to inspect each plate before it is placed in the microscope to
be sure it is free of lint and dust. This is done by reflecting light from
the safelight source. When particulate matter is seen, it can be removed
with a fine camel's-hair brush, or it can be blown away with a rubber
bulb or a freon "duster" such as is marketed by E. F. Fullam Inc.,
Schenectady, New York.
9.7. Plate Development
Almost as important as the type of plate used is the manner of its
development if suitably fine grain and good contrast are to be obtained.
In general, it is best to follow the manufacturer's recommendations,
although with some qualification. Manufacturers usually suggest a choice
of developers, one of which may particularly emphasize fine grain, another
contrast, and a third convenience. Since contrast is often the greatest
problem in electron microscopy, the developer which is selected should
feature this. Unfortunately there is inevitably a reciprocal relationship
between contrast and grain size with any particular emulsion. One cannot afford to choose the developer with greatest contrast without making
too great a sacrifice in grain, but even less can one afford to sacrifice
contrast for the finest grain developers. Truly fine grain developers lack
contrast to such a degree that they are well nigh worthless for electron
microscopy. Thus, one should select a developer tending to emphasize
contrast, but with suitably balanced characteristics.
The Kodak Company recommends D-19 as the developer of choice for
most electron microscopy. This was originally formulated for X-ray
work, and later proved desirable for aerial photography. It gives a brilliant, vivid image with less "chemical fog" than most other developers.
FIG. 37. A portion of a mitochondrion from an acinar cell of the parotid gland
of a rat (X 165, 000). (a) A micrograph made on Kodak Lantern Slide Plates, Contrast
Grade and photographically enlarged excessively (X 11) to demonstrate grain size,
(b) The same field photographed on Kodak Spectroscopic Plate, Type V-O. The original
exposure on the latter plate had to be approximately four times that of the other.
There were not, however, significant differences in the contrast values, and here both
prints are on the same grade of enlarging paper. The spectrographs plate has a
decidedly
finer
grain. However, photographic grain ordinarily is not what
limits
resolution, and in this instance the second picture does not reveal more detail than
the first. Pictorial resolution was limited by the character of the specimen, and perhaps
by the performance of the microscope. The tissue was fixed in osmium
tetroxide,
embedded in methacrylate, and was not stained.