5.13.
GLASS KNIFE MANUFACTURE
149
5.12. Knives for Ultrathin Sectioning
Most ultrathin sectioning surely is being done with glass knives which
are made to be used once and then discarded. They need not cost anything, or even if glass is purchased, the cost is small. It is a fracture edge
that is used as the knife. A trough is then built up around this, which
subsequently is filled with fluid so that sections can be floated away from
the knife edge as they are cut.
Knives made of carefully ground and polished diamonds, originally
developed by Fernandez-Moran (1956), are also commercially available.
Their cost is considerable, but they last indefinitely, although not without factory resharpening.
In most situations tissue sections cut with a diamond knife are no
better or worse than ones cut with glass, so the choice is mainly one of
expense and convenience. However, it would be easy for a novice to
destroy utterly a diamond knife by one false move, so that it probably is
wise to develop skills first with glass knives. Also, commercial supplies of
diamond knives continue to be uncertain so that there are often great
delays in receiving delivery or in having a knife resharpened. Moreover,
diamond knives are not of uniform quality and a novice hardly could
know whether or not he had a good or even a satisfactory one.
Some knowledge and skill is necessary to prepare satisfactory glass
knives which is the topic of the next three sections.
5.13. Glass Knife Manufacture
It is very easy to prepare one's own glass knives so that, for this reason
alone, it is foolish to buy them. More important, making knives oneself
is the only way to assure a truly clean edge. Almost any type of soft glass
of suitable thickness will make satisfactory knives. Easiest to get, and
certainly cheapest, is ordinary "crystal" glass, approximately ^
inch
thick, which is used for store windows of moderate size. The larger
glazing companies accumulate barrels full of trimmings of such glass
which are free for the asking, or one can buy for fairly nominal cost a
sheet of such glass and have the glazier cut it into conveniently sized
rectangles, perhaps 1 ft square. Plate glass and mirror glass also can be
used, but without particular advantage.
GLASS KNIFE MANUFACTURE
149
5.12. Knives for Ultrathin Sectioning
Most ultrathin sectioning surely is being done with glass knives which
are made to be used once and then discarded. They need not cost anything, or even if glass is purchased, the cost is small. It is a fracture edge
that is used as the knife. A trough is then built up around this, which
subsequently is filled with fluid so that sections can be floated away from
the knife edge as they are cut.
Knives made of carefully ground and polished diamonds, originally
developed by Fernandez-Moran (1956), are also commercially available.
Their cost is considerable, but they last indefinitely, although not without factory resharpening.
In most situations tissue sections cut with a diamond knife are no
better or worse than ones cut with glass, so the choice is mainly one of
expense and convenience. However, it would be easy for a novice to
destroy utterly a diamond knife by one false move, so that it probably is
wise to develop skills first with glass knives. Also, commercial supplies of
diamond knives continue to be uncertain so that there are often great
delays in receiving delivery or in having a knife resharpened. Moreover,
diamond knives are not of uniform quality and a novice hardly could
know whether or not he had a good or even a satisfactory one.
Some knowledge and skill is necessary to prepare satisfactory glass
knives which is the topic of the next three sections.
5.13. Glass Knife Manufacture
It is very easy to prepare one's own glass knives so that, for this reason
alone, it is foolish to buy them. More important, making knives oneself
is the only way to assure a truly clean edge. Almost any type of soft glass
of suitable thickness will make satisfactory knives. Easiest to get, and
certainly cheapest, is ordinary "crystal" glass, approximately ^
inch
thick, which is used for store windows of moderate size. The larger
glazing companies accumulate barrels full of trimmings of such glass
which are free for the asking, or one can buy for fairly nominal cost a
sheet of such glass and have the glazier cut it into conveniently sized
rectangles, perhaps 1 ft square. Plate glass and mirror glass also can be
used, but without particular advantage.