Haze Determination of Printing Films: Standards, Methods, and Quality Control

Haze determination of printing films is a critical optical quality control test that quantifies the degree of light scattering in transparent and semi-transparent plastic films used for printing, lamination, and flexible packaging. This article explains the measurement principle of haze, the applicable international standards such as ASTM D1003, ISO 14782, and GB/T 2410, sample preparation requirements, step-by-step testing procedures, and typical acceptance criteria, helping film producers, converters, and brand owners ensure consistent optical clarity and print quality.

Technical Overview

Haze is defined as the percentage of transmitted light that is scattered by a specimen through an angle greater than 2.5 degrees from the direction of the incident beam. In practical terms, haze describes the milky or cloudy appearance of a transparent film: the higher the haze value, the more the film diffuses light and the less clearly objects can be seen through it. Haze determination is therefore one of the most important optical performance tests for printing films used in labels, flexible packaging, window films, and display applications.

For printing films, haze directly affects the perceived quality of the finished product. Excessive haze reduces the see-through clarity of packaging windows, softens the contrast of reverse-printed graphics, and degrades the readability of text viewed through the film. Haze originates from several sources, including polymer crystallinity and spherulites, inorganic antiblock and slip additives, filler dispersion, surface texture, coating layers, ink pigment dispersion, and lamination adhesive irregularities.

Haze is measured using a hazemeter or a spectrophotometer equipped with an integrating sphere. The instrument records four luminous flux readings under standardized illumination (typically illuminant C or D65 with photopic detector response):

• T1 – incident light flux
• T2 – total light flux transmitted by the specimen
• T3 – light flux scattered by the instrument alone (blank measurement)
• T4 – total light flux transmitted by the specimen and scattered by the instrument

Total haze (%) = (T4/T2 − T3/T1) × 100. Luminous transmittance (%) = T2/T1 × 100. Because haze and transmittance are complementary but independent properties, a film can be highly transmissive yet very hazy, or low in transmittance yet optically clear in appearance.

Testing Samples

Polyester (PET) Printing Films

Transparent and metallizable PET films are widely used for labels, thermal lamination, and flexible packaging. Optical-grade PET films typically exhibit haze values below 1–2%, while standard packaging grades may range from 2% to 5% depending on thickness and additive content.

Biaxially Oriented Polypropylene (BOPP) Films

BOPP films for label facestock, overprint lamination, and flexible packaging are commonly tested for haze. Haze levels in clear BOPP usually fall between 1.5% and 4%, while matte and opaque BOPP grades are intentionally engineered with higher haze values.

Polyolefin Shrink and Label Films

PVC, PETG, OPS, and oriented PE shrink films used for shrink sleeves and full-body labels require haze control to ensure sleeve graphics remain sharp after shrinkage. Both flat film and shrunk specimens may be evaluated.

Coated, Printed, and Laminated Films

Corona-treated, coated, printed, or laminated film structures can also be assessed. Testing of converted films helps quantify the optical impact of coatings, ink layers, adhesives, and lamination processing, and supports troubleshooting when clarity problems arise downstream.

Sample Preparation and Conditioning

Proper preparation is essential for reproducible haze results:

• Cut at least three to five specimens large enough to fully cover the integrating sphere port, typically 50 mm × 50 mm or larger
• Keep surfaces free of fingerprints, dust, scratches, and static attraction, as surface contamination artificially raises haze
• Condition specimens at 23 ± 2 °C and 50 ± 5% relative humidity for a minimum of 40 hours in accordance with ISO 291 or ASTM D618, unless otherwise specified
• Report the nominal thickness of each specimen, since haze increases with thickness due to bulk scattering
• Test unwounded, non-creased areas, and mark the measurement side when surface treatments differ on each face

Testing Items

A comprehensive optical evaluation of printing films typically includes the following measurands:

• Total haze (%) – wide-angle light scattering beyond 2.5 degrees
• Luminous transmittance (%) – total visible light passing through the film
• Clarity – narrow-angle scattering affecting image sharpness through the film
• Compensated haze – haze corrected for specimen luminescence where required

Total Haze

Total haze is the primary reported parameter. It integrates all scattered light between 2.5 degrees and approximately 90 degrees and is the value specified in most purchase specifications for transparent printing films.

Luminous Transmittance

Luminous transmittance quantifies how much visible light passes through the film regardless of scattering direction. High transmittance combined with low haze characterizes a genuinely clear film suitable for premium print and display applications.

Testing Methods

ASTM D1003 – Method A (Hazemeter)

ASTM D1003 Method A employs a dedicated hazemeter with an integrating sphere, a light trap for diffuse-only readings, and standardized illumination. The method provides rapid, repeatable measurement of both haze and luminous transmittance, and offers optional compensation to remove the contribution of specimen luminescence. It is the most widely referenced method for transparent plastics in North America and in global supply chains.

ASTM D1003 – Method B (Spectrophotometer)

Method B uses a spectrophotometer fitted with an integrating sphere to measure regular (specular-included and specular-excluded) transmittance, from which haze is calculated. This approach allows full spectral analysis and is useful when characterizing tinted or lightly colored films.

ISO 14782

ISO 14782 specifies the determination of haze for transparent plastics using the same four-flux measuring principle. It is the preferred method in European and international commerce and is technically aligned with ASTM D1003, though small differences in sphere geometry and reporting conventions may exist between the two standards.

GB/T 2410 and Related National Standards

GB/T 2410 is the Chinese national standard for the determination of light transmittance and haze of transparent plastics and is harmonized in principle with ASTM D1003 and ISO 14782. JIS K 7136 and JIS K 7361-1 are the corresponding Japanese standards for haze and total luminous transmittance. Results from these methods are generally comparable when specimen preparation and conditioning are aligned.

General Measurement Procedure

• Calibrate the instrument using certified haze and transmittance reference standards, performing zero and full-scale checks before each test session
• Measure T1 and T3 without a specimen to establish the baseline and instrument scattering correction
• Mount the conditioned specimen flat against the sphere port without stretching, wrinkles, or air gaps
• Record T2 and T4 for each specimen and calculate haze and transmittance
• Test at least three to five specimens from different positions across the web and report individual and mean values
• Document the test standard, film type, nominal thickness, conditioning, and any deviations from the standard method

Factors Affecting Results

• Specimen thickness – thicker films show higher haze due to increased bulk scattering
• Surface texture – matte finishes and antiblock particles scatter light at the surface
• Additive content and dispersion – slip, antiblock, and filler particles are major haze contributors
• Corona or plasma treatment – heavy treatment can micro-roughen the surface and raise haze
• Printing and converting effects – ink pigment dispersion, ink film thickness, adhesive clarity, and nip pressure uniformity in lamination all influence the final haze of converted film
• Environmental handling – dust, static, and fingerprints on the measurement surface can inflate results

Applications

Haze determination supports quality control and material qualification across the printing and packaging value chain:

• Flexible packaging – verifying the clarity of window films and reverse-printed laminates for food and consumer goods
• Pressure-sensitive labels – qualifying clear PET, BOPP, and PE facestocks for no-label-look applications where optical clarity is critical
• Shrink sleeves – confirming that PETG, PVC, and OPS films retain low haze after printing and shrinking
• Overlamination films – ensuring protective laminating films do not dull the underlying printed image
• Display and electronics – controlling haze in protective films, optical films, and printable electronic substrates where specifications often demand haze below 1–2%
• Process troubleshooting – comparing haze before and after extrusion, treatment, printing, or lamination to identify the source of clarity loss

Manufacturers, converters, and brand owners routinely engage accredited third-party laboratories to perform haze determination when independent verification, supplier qualification, or dispute resolution is required.

FAQ

What is the difference between haze and transmittance?

Transmittance measures the total percentage of incident light that passes through the film, while haze measures only the fraction of transmitted light that is scattered more than 2.5 degrees from the incident direction. A film can transmit a high percentage of light yet appear cloudy if haze is high, so both parameters should be evaluated together.

What haze value is acceptable for printing films?

Acceptance limits depend on the application. Optical and display films typically require haze below 1–2%, premium clear label films commonly specify haze below 2–3%, general packaging films may allow 3–5%, and matte or specialty diffusion films intentionally carry haze values of 30% or more. The specification should always state the test standard and the nominal thickness at which the limit applies.

Does film thickness affect haze results?

Yes. Haze increases with thickness because scattering occurs throughout the bulk of the material. Comparisons between films are only valid at equal nominal thickness, and the thickness must always be reported alongside the haze value.

Can haze be measured directly over printed ink areas?

Standard haze methods are intended for transparent specimens. Opaque or heavily inked areas block the light beam and produce misleading results, so testing is normally performed on unprinted regions, clear windows, or transparent sections of the film. Lightly tinted films can be evaluated using spectrophotometric methods with appropriate interpretation.

Which standard should be selected for haze testing?

The choice depends on the market and customer specification: ASTM D1003 is common in North America, ISO 14782 in Europe and international trade, GB/T 2410 in China, and JIS K 7136 in Japan. Because the methods are technically aligned, agreement on a single standard, specimen thickness, and conditioning protocol before testing ensures consistent, comparable results.

How can haze in printing films be reduced?

Effective measures include optimizing polymer resin clarity and melt temperature, minimizing or refining antiblock particle size and loading, improving dispersion of additives and pigments, controlling line speed and quenching to limit crystallinity, reducing surface treatment intensity, and ensuring uniform, bubble-free adhesive application during lamination.