FAQ: “What is a visual limit for Haze%? When should I be able to see a difference in a sample?”
Haze% per ASTM D1003 measures the degree of scattering in a material. A perfect clear of 0% would be air for transparent solids and for transparent liquids, the transmission cell filled with DI water for transparent liquids represents a perfect clear.
It should also be noted that the Haze% measurement of scatter in a sample is dependent on the thickness of transparent solid samples or cell path length of transparent liquid samples.
The answer as to when you can see a visual difference will depend on the nature of the sample. For the plastic or glass sheets used in computer tablet screens, acceptable limits for what is faintly visible fall in the 1-2% range.
For pharmaceutical or chemical liquids, the average person may be able to see a visual difference in transmission haze at around 4 – 5%, and should definitely see a difference at a level of 6 – 7%.
To determine this for your sample, do a visual evaluation using a product rang exhibiting haze and take the consensus opinion of a number of people as to which samples exhibit visible haze. Measure Haze% using a sphere instrument and assign a visible limit specific to your product.
For many applications, especially those related to consumer products, a visible limit for haze may also be the tolerance for what is acceptable product.
Depending on the end use of the product, what is an acceptable may be below a visible limit if you don’t customer to see any visible haze difference in your product.
Or, if haze is inherent in the product and whatever is causing the product haze does not impact its use, an acceptable tolerance may be several times a visible difference. On these types of products, a typical range for good product might be from 10 to 12%, with an upper limit set at 20% just to ensure that any abnormal product above that is detected.
Air for transparent solids, or the cell filled with DI water or clear solvent for transparent liquids, is a physical product reference representing no haze (Haze% = 0), and the best your sample can be. A visible limit in product samples will typically be in the 2% to 5% range. What is acceptable in the marketplace will vary from less than a visible limit to some upper maximum.