EMS Technical Data Sheets

Glass Knife Pliers

EMS Catalog #62190-01

These pliers are very useful in the preparation of glass knives for ultramicrotomy. The jaws are ground with a long radius in the transverse direction. With practice, both the direction and quality of the free-break can be effectively controlled, facilitating the production of high quality knives for ultramicrotomy.


  1. Wash the glass to be broken in hot water and detergent. Rinse Thoroughly. Hand dry with a lint-free cloth or air dry in a dust-free environment. Do not handle the cleaned glass with your fingers; use nylon or fine cotton gloves.
  2. Use a clean paper mat, such as a specimen preparation mat, to work on. Keep this paper free of dirt or glass chips. Lay out the glass to be broken. 1"x 1" pieces are made first.
  3. Make short (1/4"-1/2") score marks using a wheel-type or pen-type scorer. Gently draw the scorer across the glass. Too much pressure will gouge and chip both the glass and the scorer, adversely affecting the quality the break. Try to make the score marks as straight and as close to the desired direction of the break as possible. A scoring guide is essential.
  4. Make sure that the jaws of the pliers are free of glass chips, dirt or rust. Place the glass between the jaws so that the fulcrum notch is directly in line with the score mark. The jaws must also be absolutely perpendicular to the score mark (see diagram). Apply firm but steady pressure to the plier jaws. If breakage does not occur, release the pressure and begin step 4 again. If breakage still does not occur, move to another region of glass do not try to rescore the glass.
  5. Carefully, select the edges of the 1"x 1" squares that are the straightest and have the fewest stress marks. A stressed break will leave visible hash marks in the glass when viewed from the side.
  6. Carefully and gently make the final ¼" score mark as shown. This score mark should coincide with an approximate 45° diagonal from corner to corner. The free break will tail away slightly from this axis. One may wish to score slightly off this axis in order to direct the break to a desired side (see diagram).
  7. Position the pliers as shown. Apply slowly increasing pressure until a break is seen or heard. Relax the pressure without letting go of the glass. With your free hand, making sure that the knife edge(s) do not touch anything. Inspect the knife-edge under a microscope to determine its quality. Store in a dust free environment.

Online Ordering

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