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GASP® Surface Polarimeter – Measure Surface Stress in Tempered, Heat-Strengthened, or Annealed Glass in Accordance with ASTM C1048

Strainoptics’ GASP® Polarimeter is a portable instrument for measuring surface stress in heat-strengthened and tempered glass. It can also be used to confirm stress-relief in annealed glass and to validate furnace settings for manufacturers of safety glass.

Our most current model is the LCD-GASP (shown at left), which is the ideal solution for applications where a large volume of measurements are made daily. It is battery-operated and comes with a CCD video camera and a built-in LCD display to eliminate operator eye fatigue and parallax errors. Conversions from Laser GASPs to LCD-GASPs are available and recommended!

Each Strainoptics LCD-GASP Surface Stress Polarimeter is:

  • Non-destructive
  • Easy to operate
  • Compliant with all industry specifications, including ASTM C1048, C1279 and the new compulsory
    EN-12150 and EN-1863 standards and CE marking requirements for testing mechanical strength in architectural glass
  • For in-plant or field use
  • Easily used by multiple people at once
  • Easily used on vertical glass surfaces
  • Available for flat or curved surfaces
  • Ideal for solar glass applications

Options & Accessories

Laser GASP

If you don’t need the LCD monitor, we still offer our standard, tried-and-true Laser GASP. The Laser GASP Surface Stress Polarimeter has an eyepiece instead of an LCD screen and just as portable and reliable as the LCD-GASP.


Standard GASP polarimeters are for flat or slightly curved surfaces, while the GASP-CS is designed to accommodate glass with a radius of less than a 200mm (~8 inches). The GASP-CS may also come with an LCD screen, the LCD-GASP-CS.

While standard GASP models have a broad measurement range of up to 25,000 psi (180 MPa) and are primarily for meant for heat-strengthened or tempered glass, Strainoptics also sells high-sensitivity GASPs, GASP-HS or LCD-GASP-HS, for measuring annealed glass. The GASP-HS comes with a 2X measuring wedge and measures up to 12,500 psi (90 MPa).


NOW for HEAT-STRENGTHENED OR TEMPERED GLASS! AUTO-GASP…now you can automatically measure surface stress per ASTM C1048 and C1279 with Point-and-Click Speed and Convenience after setting up the GASP Polarimeter on the uncoated tin side of your glass.

  • Includes Video GASP, licensed software, and cables.
  • Conversion kit available for existing Video GASP or Laser GASP customers.
  • Works with Windows XP or Windows 7 desktop or laptop computers with two available USB ports.
  • No data board required.
  • Stores images and data for later retrieval and/or analysis.
  • Multiple licenses available.

NOTE: The accuracy of measurements using the AUTO-GASP is dependent upon the quality of the image obtained by the operator and the composition of the glass. Strainoptics will gladly evaluate your samples for suitability free of charge.

UV Lamps

for detecting the tin side of float glass:

  • UV-STI-26 Rechargeable Double-Tube Ultraviolet Lamp
  • UV-STI-1301 Mini Ultraviolet Lamp

CAL-PLATE Accessory

  • Glass reference standard with certified surface stress value
  • Enables verification of instrument accuracy
  • Ideal for operator training
  • Available for standard and high-sensitivity GASP wedges

Refractive Index Matching Fluid:

  • Available in 4 oz (120 cc), 16 oz (473 cc), or 1 gal (3785 cc) sizes
  • RI = 1.54 for use with GASP only – (For immersion cells, specify RI = 1.52)


The GASP-STAND accessory is a portable benchtop platform that safely holds any Strainoptics Laser GASP® surface polarimeter when out of its carry case and not in use. It protects the instrument’s prisms from accidental damage and comes with a refillable plastic dispenser bottle and holder for GASP index matching fluid.

GASP and Index Matching Fluid Not Included


Each GASP comes in a heavy duty plastic case with protective foam packaging and the Strainoptics logo stamped right into it. They are tough to damage but if you need a replacement case or a spare, we always have them in stock.