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VARISTEM Blasting Improvement Products wedge between the stemming and blasting material, slowing escape of gas through the drill hole. VARISTEM contains the explosive energy within the rock mass where it belongs!

VARISTEM Plugs work by creating a blocking effect within the drill hole by wedging the stemming material between the drill hole wall and our plug. Upon detonation of the explosives, the plug is forced upward into the stemming material and "locks up". The explosive gases and energy are prevented from traveling (venting) up through the drill hole, and instead are contained within the rock mass for milliseconds longer than non-plugged blasts!

Introduction to Varistem blasting plugs

Design and installation of stemming plugs

Increased Fragmentation, Fracturing and Cap Rock Breakage. Reductions in Fly Rock, Air Blast, Stemming Ejection, Dust, Noise and Oversized Rock. These are all direct benefits and results of containing the blast energy within the rock mass for milliseconds longer than normal, simply by using VARISTEM.


Larger VARISTEM plugs have a lead stem for proper alignment.
VARISTEM's Patented GEAR Design:
  • Prevents plug collapse in undersized holes or when forced over jagged rocks.
  • Makes the plug detonator cord (tube or wire) friendly. The numerous vertical grooves on the outside diameter of the plug prevent the detonator cord from being crushed, nicked or pulled into the drill hole during insertion. (The cord will simply slip into one of the vertical grooves.)
  • Gives structural strength to the plug.
  • Allows a compressed hold when used in air decking.

Easy To Install:

These plugs should be inserted point-down. Using a standard loading/charge pole, simply push the plug to the ANFO or Emulsion. It literally takes seconds!!!

Expensive separation of oversized rock from muck pile. (No VARISTEM Used) Left: Breaker costs are reduced with VARISTEM. Below: VARISTEM reduces delays due to oversized at the crusher.

Besides reducing the average rock diameter in the muck pile, VARISTEM saves secondary breakage costs by reducing the volume of oversized cap rock. It is possible to shorten stemming heights for improved cap rock breakage. Consistent stemming heights and reduced gas emulsions are possible with the VARISTEM in air decking.

And note the TWO PATTERN SPREAD STUDIES (HOLCIM and ALCOA), which both demonstrated savings in drilling fewer holes for the same fragmentation.