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Beyond ASTM D1003 Haze Standards Exploring Transmission Haze Metrics and Practical Considerations for Translucent Materials

The current, available ASTM D1003 Haze Standards have nominal Haze% values of 1, 5, 10, 20 and 30 with air (transparent solids) or the transmission cell filled with DI water being 0 (transparent liquids). Here are some thoughts on further options.

Thirty (30) is not a magic number but above that value, it is considered that your samples are moving from a transparent material to a translucent material.

As a metric, ASTM D1003 Transmission Haze was designed to measure scattering in near clear, transparent materials. At a level above 30, you are moving out of the intended range of the metric.

If you have an instrument that is measuring an ASTM D1003 Haze 30 standard in close agreement with assigned values, you can have a high degree of confidence that it is reading haze well above that point. However, please note that when you get above 50, you are well beyond the intended use of the metric.

At this point, we generally recommend that customers use Y Transmission (C/2, D65/10; Total Transmission mode) to separate lot differences in translucent materials.  Y Transmission measures the total amount of light that comes through the translucent material with air (transparent solids) or the transmission cell filled with DI water being 100 (transparent liquids).

If you said that you need a PQ performance Qualification standard at a Haze level > 30 to verify instrument performance, you could make your own by purchasing a chemically abraded glass sample (at least 50 mm x 50 mm in size) and benchmarking the Haze value yourself.

Glass is very stable and if kept clean should serve this purpose well.

This abraded glass sample could be measured on your instrument over time in comparison to your baseline values to verify that the instrument is consistent at this higher level of haze.

Liquid Fragrance Sample

Maintaining Color Consistency in Clear Liquids

HunterLab diffuse sphere instruments are often used to measure liquid samples, especially clear liquids. The liquid fragrance shown above is one such example of a clear liquid. The fragrances is so clear that is resembles water.

Fragrances such as this are often added to cleaning supplies, air fresheners, or other consumer products. One of the problems that this type of sample can experience is that the chemistry of the liquid fragrance solution can deteriorate and the solution will start to visually yellow. This is often a concern for manufactures because if the liquid fragrance yellows it cannot be added to the end product.

HunterLab sphere instruments can measure the transmitted color of the liquid and report the yellowness index. The liquid fragrance should be measured in a 20mm path length cell. Since the sample is very clear, near water in color, this slightly larger path length allows for the light to pass through more of the sample. This measurement method ensures that smaller differences can be measured between samples.

With the proper instrument and the appropriate accessories from HunterLab, very clear liquid samples can be accurately and repeatedly measured for color consistency.

As described in Section 6 of ASTM D1209, there are 2 criteria to validate a APHA/Pt-Co 500 standard:

• The APHA/Pt-Co 500 Color Standard must have a defined chemical composition and be prepared in accordance with section 6 of ASTM D1209.
• After preparation, the APHA/Pt-Co 500 standard must meet a absorbance criteria at 4 points in the blue region of the visible spectrum per Table 1 of ASTM D1209.

1. Platinum-Cobalt Reference Standards

6.1 Platinum-Cobalt Stock Solution— Dissolve 1.245 g of potassium chloroplatinate (K2PtCl6) and 1.00 g of cobalt chloride (CoCl2·6H2O) in water. Carefully add 100 mL of hydrochloric acid (HCl, sp gr 1.19) and dilute to 1 L with water. The absorbance of the 500 platinum-cobalt stock solution in a cell having a 10 mm light path, with reagent water in a matched cell as the reference solution, must fall within the limits given in Table 1.

HunterLab sphere instruments with CIE d/8 geometries conform to the requirements of ASTM D1003 Section 8: Procedure B Spectrophotometer. The measurement of transmission haze using Procedure B instruments will be in close agreement with ASTM D1003 Procedure A Haze meter.

Meeting ASTM D1003 Section 8 Procedure B Requirements

Here is a more detailed description of how the HunterLab UltraScan PRO and UltraScan VIS meet the requirements of Section 8.

1. Procedure B (Spectrophotometer)

8.1 Apparatus:

8.1.1 The instruments used for measurement shall meet the geometric and spectral requirement of this section.

HunterLab UltraScan VIS and UltraScan PRO instruments meet ASTM D1003 Section 8 Procedure B Spectrophotometer requirements.

8.1.2 The instrument shall be capable of computing from the spectral data the 1931 CIE tristimulus values and related color coordinates for CIE standard Illuminant C or alternatively Illuminant A.

HunterLab offers A/2 and C/2 options for calculating Haze%, Y Total and Y Diffuse luminous transmission in EasyMatch QC software.

8.1.3 The instrument shall utilize a hemispherical optical measuring system, with an integrating sphere, in which the specimen can be placed flush against the sphere port. The surfaces of the interior of the integrating sphere, baffles, and reflectance standards shall be matte, of substantially equal reflectance and highly reflecting throughout the visible wavelengths.

HunterLab UltraScan VIS and UltraScan PRO sensors and internal components are coated with Spectralon having a 99%+ reflectance. Transparent specimens for haze measurement are placed at the TTRAN port, flush against the sphere.

The UltraScan VIS and Pro come with white, Japanese commercial opal reflectance standard of 99%+ reflectance.

8.1.4 Two geometries can be used: unidirectional illumination with diffuse viewing and diffuse illumination with unidirectional viewing. Using diffuse illumination with unidirectional viewing, the following apply:

HunterLab UltraScan VIS and UltraScan PRO sensors have a diffuse illumination with unidirectional viewing (8°) geometry. They are referred to as CIE-conforming diffuse d/8° sphere instruments.

8.1.4.1 Use an integrating sphere to illuminate the specimen diffusely; the sphere may be of any diameter as long as the total port areas do not exceed 4.0 % of the internal reflecting area of the sphere. The specimen and light trap ports of the sphere shall be centered on the same great circle of the sphere, and there shall be at least 2.97 rad (170°) of arc between their centers.

The light trap port shall subtend an angle of 0.14 rad (8°) at the center of the specimen port along the wowing beam. With the light trap in position, without specimen the axis of the viewing beam shall pass through the centers of the specimen and light trap ports.

Haze 30 standard (R) as part of a D1003- calibrated set (L) of 1%, 5%, 10%, 20%, 30% haze standards (HL# CMR-2760).

FAQ: “We have a scientist here who is looking at films containing small bubbles and attempting to do measure them by measuring Haze% on a HunterLab spectrophotometer. I suspect her problem in obtaining numbers that “make sense” from what you get from just eyeballing the samples (and trying to look through them at the outlines of a object behind the film to gage the amount of regular transmittance) is that her samples have Haze% > 30 %, which means that a spectrophotometer (or even a haze meter) isn’t the appropriate tool to use for the analysis.

How is transmission haze measured at levels > 30%?”

Nessler Rack with 0-30-100-200-300-400-500 APHA Pt-Co Hazen liquid color standards

Contact for APHA/Pt-Co/Hazen Color Testing

Contact the following and ask for “APHA/Pt-Co/Hazen Color testing per ASTM D1209 and D5386″.

Dallas Laboratories, Inc.

Dallas, TX 75215 USA
+214-421-1400
www.associatedlabs.com

Two global test labs are:

Intertek – Deer Park Lab
Deer Park, TX 77536 USA
+281 971 5600
www.intertek.com/petroleum

SGS North America Inc.
Houston, TX 77058 USA
+281-291-8392
www.sgsgroup.us.com

FAQ: ” We are currently using a 10 mm path length and read in the 0 – 50 region for APHA/Pt-Co/Hazen Color, usually in the area of 10. Would you recommend a 10 mm path length with our equipment for this application?”

“APHA Color” is also known by two other names – “Pt-Co Color” and “Hazen units (HU)”. All three names represent the same color scale. As the APHA/Pt-Co/Hazen Color is dependent on the path length or thickness of the sample, it is important to:

• Use the same cell path length for all measurements.
• Report the cell path length as part of the measurement method if inter-instrument agreement of APHA/PtCo/Hazen Color values is important at multiple sites.

HunterLab’s instrument correlation to the visual APHA/Pt-Co/Hazen Color scale per ASTM D5386 allows the user to select a 10-mm, 20-mm or 50-mm path length cell by configuring the Color Data View in EasyMatch QC software to display “APHA-10mm”, “APHA-20mm” or “APHA-50mm”.

While any of these three cell path lengths can be used to effectively measure APHA/Pt-Co/Hazen Color, the optimal choice for cell path length choice is based on the following criteria:

• A 10-mm path length cell is typically used for highly saturated or chromatic liquids, typically with APHA/Pt-Co/Hazen Color values > 300.
• The easy-to-fill 20-mm path length cell is used for moderately chromatic liquids, and is the default cell path length when a wide APHA/Pt-Co/Hazen Color range of liquid colors is being measured from 0 (distilled water) to 500.
• The longer 50-mm path length cell is preferred for clear or near clear liquids where APHA/Pt-Co/Hazen Color values < 30, and especially when APHA < 10.