The glass being a non-reactive material is a perfect fit for spheres where chemicals are used widely. In Chemistry labs, packaging, storing, pharmaceutical packaging, both ceramics and glass hold a special importance. And both these materials have volatile behavior when subjected to internal strain due to an external force. It is said that a strained material may remain silent or be a dud or may rupture unexpectedly. To avoid any devastating aftereffect of product failure, it is better to test the products before using it. For testing strain in the glass, Polariscope is the best testing instrument to use.

How does a Polariscope work?

It is nothing but a simple device having 2 polaroid glass sheets. These glass sheets have parallel lines of electrons that only allows parallel rays of light to pass through it. Rest of the rays get absorbed by parallel lines of electron and no light can be seen on the other side. A polariscope assembly has 2 polaroid sheets and a light source. Both the polaroid sheets have parallel lines along their axis. which is to be tested here are not doubly refractive unless strained. So, when you place a test sample in between the polaroid sheet and light, it should pass the light. If it has some strain, the light ray would get deflected from its path and thus absorbed by the other sheet. Hence no light or black impression will be seen on the other side.

Polariscope strain viewer is a very simple to operate the device, but a strong observation is required to analyze the test sample. However, there are now many advanced models come up in which analyzing the sample is very easy.

Labtiger offer different models for strain analysis depending upon the material to be tested and features incorporated.

Polariscope Strain Viewer for Glass and Plastics – PSPL G20

This is the latest model launched and it has the capability to test Glass and plastics. The body of the strain viewer is compact and perfect for articles made up of glass, like decorative pieces, test tubes, beakers, glass utensils and may be for gems. You just need to put the specimen in between the light and polaroid sheet. As soon the light passes through the sample it forms a rainbow like an effect around the area that has been subjected to strain. The diameter of field view is 190 mm.

Polariscope DX Model offered by Labtiger

This device is perfect for testing PET preforms. Since plastic has the tendency to refract the light doubly through a strained area. The Polaroid glass has 2 slots to keep the test sample having to measure the angle of 45° and 90°. As strain may appear differently from different angles. It works on the same principle as PSPL G20 works. The viewing area is 260mmX240mm. It is equipped with 2 lights, Monochromatic light and sodium lamp, which helps in sharp and clear viewing.

The USP of this model is that it’s a computerized model and gives pictorial view via software, images can be captured and transferred easily. It gives provision to the operator to refer the sampled images with pre-loaded images of defects. Easy data logging and recalling facility are available. It’s a table top model and approx. the weight of the device is 20kgs.

Why there arise a need of Strain testing in glass?

Testing is an important aspect of quality check process. In the glass, there are certain defects like ridges and furrows that can be analyzed with naked eyes. But the internal strain is very difficult to point. Also, it can be assumed that any strain related defect cannot sustain very long. It may crack or rupture as soon subject to high temperature or pressure, which otherwise is acceptable for it. Let’s say, a lot of glass bottles is manufactured for transporting acid to be used in school laboratories. You cannot take the chance of skipping the quality test. If there is a strain in one bottle, the whole lot may get damaged due to stacking load or impacts during transit; which otherwise is supposed to bear it.

Also, glass experience contraction and expansion due to the extreme change in temperature. Decorative items which often get imported and exported need to undergo stringent quality checks. Otherwise, they may tend to damage from strained areas if transported via sea or air media, as there are sever hot and cold transitions. Having a polariscope or setting up a quality check lab may require set up cost, but this would save your bucks which you may lose due to damaged and rejected consignments. Also, this would affect your brand name in the longer run.

Is Polariscope for gemologists?

Polariscope is, in fact, gaining popularity among gemology industry. Because it can efficiently judge the defects at the molecular level which decrement the cost of the gem by many folds. This device is very compact in size and efficient in observation which is why it is making its position strong among the gemmologists.