Fogging Test Glass Plates: A Critical Consumable for Automotive Fog Testing
When automotive interior materials are evaluated for fogging, the glass plate used in the test may appear to be a simple piece of laboratory glass. In reality, the fogging test plate is a precision test component and a critical part of the measurement system.
Schap Specialty Machine manufactures fogging test equipment used by automotive laboratories, material suppliers, and testing organizations around the world. Because the glass plate is directly involved in collecting and measuring the condensable material produced by the test specimen, Schap also supplies replacement fogging glass plates as a laboratory consumable.
What Is a Fogging Test Plate?
Automotive fogging tests are designed to determine whether volatile and semi-volatile components released from interior materials will condense on a cooler surface.
During a typical photometric fogging test, a material specimen is heated while a glass plate above the specimen is maintained at a lower temperature. Volatile components released from the specimen migrate toward the cooler glass surface and condense there.
The resulting deposit is then evaluated optically.
Depending on the applicable standard, the measurement may involve:
- Specular reflectance or gloss
- Haze or light transmission
- Visual examination of the condensate
- Comparison of the glass plate before and after testing
ISO 17071, for example, describes a reflectometric method in which volatile components condense on a cold glass surface and their light-scattering characteristics are evaluated. (ISO)
ISO 6452 likewise describes measurement of fog condensate on glass surfaces and specifically recognizes that the behavior of the condensate can affect the accuracy of the measurement. (ISO)
This makes the glass plate much more than a container lid. It is the measurement surface on which the fogging phenomenon is quantified.
Why Ordinary Glass Is Not Suitable
A common misconception is that any clean piece of glass can be substituted for a fogging test plate.
That is not the case.
The glass used for photometric fogging must have controlled characteristics because differences in the glass can introduce variation into the measurement.
For example, ISO 6452:2021 specifies float glass of appropriate quality with a thickness of 3 ± 0.2 mm. The standard specifies either minimum square dimensions of 110 × 110 mm or a circular plate approximately 103 mm in diameter. It also requires identification of the tin and non-tin surfaces and specifies limits on the variation of gloss values between plates. (iTeh Standards)
SAE J1756 similarly specifies float glass plates approximately 3 mm thick and requires the tin and non-tin surfaces to be identified. (Scribd)
These requirements exist because the optical surface of the plate is part of the test.
The Tin Side and Non-Tin Side Matter
Float glass is manufactured by floating molten glass on a bath of molten tin. As a result, the two sides of the finished glass are not necessarily equivalent for fogging measurements.
Fogging standards therefore distinguish between the tin side and the non-tin side.
The non-tin side is generally used as the test surface in the applicable photometric methods.
The two surfaces can be distinguished using ultraviolet light. The tin side exhibits a characteristic fluorescence, allowing the surfaces to be identified. SAE J1756 specifically describes this identification process and requires the appropriate surface to face the specimen. (Scribd)
This is an important reason why a replacement plate should be properly prepared and identified rather than simply cut from a piece of ordinary window glass.
Optical Characteristics Are Important
The fogging measurement is based on detecting a change in the optical behavior of the glass surface.
Before the test, the clean plate has a known optical characteristic. After exposure to the test specimen, condensable material deposited on the plate changes that characteristic.
For reflectometric testing, the difference between the initial and final readings is used to calculate the fogging value.
Consequently, variations in the original surface condition of the glass can affect the measurement.
ISO 6452:2021 recognizes this by specifying that the gloss values of the plates used in a test series must be closely matched. (iTeh Standards)
In other words:
The glass plate must be consistent before the test so that the change measured after the test can be attributed to the test specimen rather than to the plate.
Cleaning Is a Critical Part of Plate Preparation
Perhaps the most important characteristic of a fogging test plate is something that cannot be seen easily: surface cleanliness.
A fingerprint, dust particle, cleaning residue, oil film, or other contamination can change the way condensate spreads across the glass.
This is especially important because fogging is strongly influenced by the interaction between the condensate and the glass surface.
The older DIN 75201 procedure, for example, includes specific cleaning and surface-wettability checks for the glass plates. The standard notes that the fogging result is strongly influenced by the wettability of the glass surface. (Scribd)
Therefore, proper preparation is not simply a matter of making the glass “look clean.”
The objective is to produce a reproducible test surface.
Handling the Plates
Once a fogging plate has been properly cleaned, handling becomes extremely important.
Laboratories should avoid touching the test surface with bare fingers. Oils from skin can remain on the glass and alter its surface characteristics.
Appropriate handling practices include:
- Handle plates by their edges.
- Use clean gloves or appropriate laboratory tongs.
- Do not touch the test surface.
- Keep plates protected from dust.
- Avoid contact between clean test surfaces.
- Store plates in a clean, controlled environment.
- Keep the designated test surface properly identified.
- Inspect plates for scratches, deposits, chips, or other damage before use.
ISO 6452:2021 specifically lists polyethylene gloves, tongs, and a desiccator among the equipment associated with the fogging procedure. (iTeh Standards)
Why Scratches and Surface Damage Matter
A fogging test depends on measuring relatively small changes in the optical characteristics of the glass surface.
A scratch or other surface defect can therefore interfere with the measurement.
The same is true for residual cleaning compounds or other contamination. Even if the plate appears visually clean, a microscopic residue can affect the wetting behavior of the condensate.
For this reason, fogging plates should be treated as precision laboratory consumables, not as reusable pieces of general-purpose glassware.
Standards That Use Fogging Glass Plates
Fogging glass plates are associated with a wide range of automotive and material-testing standards.
Schap Specialty Machine fogging equipment and replacement plates are used in applications associated with standards including:
- DIN 75201
- DIN EN 14288
- DIN EN ISO 17071
- EN 14288
- GME 60326
- GMW 3235
- HES D6508
- ISO 17071
- ISO 6452
- MS 300-54
- PV 3015
- PV 3920
- SAE J1756
- TSM 0503G
These standards cover different materials and procedures, and the exact plate dimensions, optical requirements, cleaning procedure, and test conditions should always be confirmed against the current revision of the applicable specification.
For example, EN 14288 is an older leather fogging standard that has been superseded by ISO 17071 in the European standards system. (dinmedia)
Likewise, SAE J1756 has subsequently been revised, so laboratories should always verify the revision specified by their customer or applicable test program. (ANSI Webstore)
Not All Fogging Tests Use Glass
It is also important to distinguish between the photometric/reflectometric method and the gravimetric method.
In a photometric test, the condensable material is collected on a glass plate and the resulting optical change is measured.
In a gravimetric test, condensable material is collected on aluminum foil and the increase in mass is determined.
SAE J1756 describes both approaches, while ISO 6452 also addresses measurement using glass and aluminum foil. (ANSI Webstore)
Therefore, a laboratory performing gravimetric fogging does not necessarily consume glass plates in the same manner as a laboratory performing photometric fogging.
For laboratories performing the photometric method, however, the glass plate is an essential test consumable.
Why Fogging Plates Eventually Need to Be Replaced
Even when handled carefully, fogging plates do not necessarily remain suitable indefinitely.
Repeated cleaning and handling can eventually produce:
- Fine scratches
- Surface wear
- Changes in surface characteristics
- Persistent contamination
- Optical variation
- Damage to the edges
- Uncertainty about the plate’s cleaning history
A plate that produces questionable or inconsistent results should not simply be reused because it “looks good.”
Replacing the plate provides the laboratory with a known, controlled test surface and helps maintain repeatability.
This is particularly important in laboratories conducting large numbers of automotive material qualification tests, where small sources of variation can become significant over many tests.
Schap Specialty Machine Supplies Fogging Plates as a Consumable
Schap Specialty Machine recognizes that the fogging glass plate is an integral part of the photometric test system.
For this reason, Schap supplies replacement fogging plates separately from the fogging tester.
This allows laboratories to maintain an inventory of properly specified plates and replace them when required rather than attempting to fabricate or source ordinary glass locally.
Schap’s replacement plates are intended for use with its fogging equipment and for applications requiring the controlled glass surface used in automotive fogging measurements.
View Schap fogging-test standards and related products
A Small Component With a Big Effect
The fogging glass plate may be one of the smallest components in an automotive fogging laboratory, but it can have a significant effect on test quality.
The plate must have appropriate:
Material → Dimensions → Thickness → Surface characteristics → Optical properties → Surface identification → Cleanliness → Handling
All of these factors contribute to obtaining reliable and repeatable results.
When a laboratory performs photometric fogging testing, the glass plate should therefore be considered part of the measurement system, not merely a piece of disposable glassware.
The Schap Advantage
Schap Specialty Machine has been supplying automotive and materials-testing equipment to laboratories for decades. By providing replacement fogging glass plates as a consumable, Schap helps laboratories maintain the test equipment and materials necessary for continued fogging testing.
For laboratories performing automotive interior fogging tests, keeping an adequate supply of properly specified replacement plates on hand can be a simple way to avoid unnecessary interruptions and help maintain consistent test conditions.
When the glass plate is part of the measurement, the quality of the glass matters.
Related Fogging Standards
Schap Specialty Machine supports fogging-test applications associated with numerous automotive standards, including [DIN 75201], [DIN EN 14288], [DIN EN ISO 17071], [EN 14288], [GME 60326], [GMW 3235], [HES D6508], [ISO 17071], [ISO 6452], [MS300-54], [PV 3015], [PV3920], [SAE J1756], and [TSM 0503G].
Standards are periodically revised or superseded. Always verify the current revision and customer-specific requirements before testing.
Schap Specialty Machine — Fogging Test Equipment and Consumables for Automotive Materials Testing.
