Methods of test for clear finishes for wooden furniture, Part 5: Test for low-angle glare

IS 5807 Part 5 - Foreword Key Points & Specifications

• Purpose:
  Measures low-angle glare (specular reflection) from clear finishes on wooden furniture surfaces, important for high-illumination environments (schools, halls).

• Scope:
  Quantitative test expressing glare as % reflection from a coated panel or finished furniture surface.

• Basis:
  Adapted from BS 3962 Part I (1965), harmonized with international standards and Indian practices.

• Related Standards in Series:

  Part	Test Focus	Year
  I	Resistance to dry heat	1975
  II	Resistance to wet heat	1975
  III	Resistance to marking by oils and fats	1971
  IV	Resistance to marking by liquids	1975
  V	Test for low-angle glare	1975

• Clause 4.2: Requires purchaser-seller agreement on test conditions.

• Reporting:
  Calculate and report mean glare values for each direction tested (Clause 5.5).

Formula for Mean Reflection Percentage

[ \text{Mean Reflection} = \frac{\sum_{i=1}^n R_i}{n} ]

• Where ( R_i ) = reflection % in direction ( i ),
• ( n ) = number of directions tested.

flowchart LR
    A[Start: Select test surface] --> B[Measure specular reflection at low angle]
    B --> C[Record reflection % in multiple directions]
    C --> D[Calculate mean reflection %]
    D --> E[Report glare value]

This standard ensures glare from furniture finishes is quantified to avoid visual discomfort in illuminated spaces.

IS 5807 Part 5 (1975) — Scope & Key Specifications for Low-Angle Glare Test

Scope:

• Measures low-angle glare (specular reflection) from clear finishes on wood furniture.
• Quantitative result: percentage reflection under controlled conditions.
• Applicable to flat surfaces of finished wood panels or furniture.

Key Specifications:

Optical Arrangement Summary (Fig. 1):

flowchart LR
    LightSource -->|Collimated Beam (16 mm)| Lens1
    Lens1 -->|Beam at 80° to surface| TestSurface
    TestSurface -->|Reflected Beam| Lens2
    Lens2 --> Photocell
    Photocell -.->|Signal| MeasurementDevice

Notes:

• Gloss standard is defined as 100 units.
• Calibration against plane polished black glass ensures 99-101 gloss units.
• Exact positioning of light source adjustable ± short distance around 31 mm focal length.
• No image limiting aperture plate in receiving system.

This setup ensures consistent, repeatable glare measurement for quality control of wood finishes.

IS 5807 Part 5 - Apparatus for Measuring Low-Angle Glare

Key Specifications:

• Light Source & Lens:

  • Collimated beam diameter: 16 mm
  • Lens focal length: 31 ± 1 mm
  • Light source position adjustable around 31 mm from lens axis
  • Light source aligned on optical axis for symmetrical illumination

• Beam and Receiving System Geometry:

  • Incident beam angle to surface normal: 80°
  • Receiving lens focal length: 31 ± 1 mm
  • Receiving system axis nominally at 80° to normal, adjustable ±1-2°
  • Lens diameter subtends angle: 8° 40' ± 20' at beam-surface intersection

• Photocell:

  • Positioned 50 mm from receiving lens
  • Photocell diameter ≥ lens diameter
  • Photocell plane perpendicular to lens axis
  • Enclosed in blackened tubular container to avoid stray light

• Power Supply:

  • Constant voltage supply required for search unit operation

Gloss Standard:

• Reference gloss = 100 units
• Other glasses acceptable if calibrated within 99 to 101 units

Summary Diagram (Optical Path):

graph LR
A[Light Source] -- Collimated Beam (16 mm) --> B(Lens, f=31 mm)
B -- Beam at 80° --> C[Test Surface]
C -- Reflected Beam at 80° --> D(Receiving Lens, f=31 mm)
D -- Focused Light --> E[Photocell (50 mm from lens)]

This setup ensures precise measurement of low-angle glare on wood finishes as per IS 5807 Part 5.

IS 5807 Part 5 - Glossmeter & Gloss Standard Summary

Glossmeter Setup (Clause 2.1.1 & 5.2)

• Incident & reflected light beams at 80° to the surface normal.
• Photocell aligned in the same plane as the incident beam.
• Output fed to a galvanometer scaled 0 to 100 units.
• Full scale (100 units) set using the Gloss Standard.
• Test surface gloss expressed as % relative to the standard.

Gloss Standard Specs (Clause 3.2 & 3.2.1)

• Material: Highly polished clear glass.
• Flatness: Within 2 fringes/cm.
• Refractive index: ND = 1.523 ± 0.002.
• Dimensions: Same as the base of the search unit.
• Back & edges: Roughened and painted black to avoid stray light.
• Gloss value of standard: 100 units.
• Other glasses allowed only if calibrated between 99 and 101 units.

Procedure

1. Place glossmeter on the gloss standard.
2. Adjust photocell angle for maximum galvanometer reading.
3. Set galvanometer to 100 units.
4. Place instrument on test surface, ensure good contact.
5. Record galvanometer reading as % gloss relative to standard.

flowchart LR
    A[Glossmeter setup] --> B[Incident beam @ 80°]
    B --> C[Reflected beam @ 80°]
    C --> D[Photocell collects reflected light]
    D --> E[Galvanometer output (0-100 units)]
    E --> F[Calibration on Gloss Standard (100 units)]
    F --> G[Measure test surface gloss (% relative)]

This ensures consistent, reproducible gloss measurement as per IS 5807 Part 5.

IS 5807 Part 5 (1975) – Preparation of Test Surface: Key Points

1. Gloss Standard

• Gloss standard = 100 units (Clause 3.2.1).
• Alternative glasses allowed if calibrated to give gloss values between 99 and 101 units.

2. Test Surface Preparation (Clause 4)

• Apply the full finishing system as per IS 2338 (Part 1) - 1967 on a wooden substrate.
• Surface must be flat and large enough for the gloss meter’s search unit to stand without overlap.
• Final coat aging conditions:
  • Temperature: 27 ± 2°C
  • Relative Humidity: 65 ± 5%
  • Duration: Minimum 28 days (can be reduced if agreed).
• For matt finishes, abrasion can be done on the final product.

3. Test Procedure (Clause 5.3)

• Take measurements on 6 representative areas.
• Measurement plane must be parallel to the wood grain direction.

Summary Table

flowchart TD
    A[Wooden substrate] --> B[Apply finishing system (IS 2338 Part 1)]
    B --> C[Allow aging: 27±2°C, 65±5% RH, ≥28 days]
    C --> D[Surface ready for gloss test]
    D --> E[Measure gloss at 6 areas]
    E --> F[Measurement plane || grain direction]

IS 5807 Part 5 - Test Procedure Summary

Key Specifications (Clause 4.2)

• Aging conditions for final coat:
  • Temperature: 27 ± 2°C
  • Relative Humidity: 65 ± 5%
  • Duration: ≥ 28 days (can be reduced by mutual agreement)
• Surface finish: For matte finishes via abrasion, test on the finished furniture surface.

Gloss Measurement (Clause 3.2.1)

• Gloss standard = 100 units (using plane polished black or blackened plate glass)
• Alternative glasses allowed only if calibrated to 99-101 units against the standard.

Test Procedure Highlights (Clause 5)

• The test involves measuring gloss or low-angle glare on the prepared surface.
• The surface must be conditioned as per Clause 4.2 before testing.
• Calibration of gloss meters against the standard is essential.

Gloss Calibration Table (Conceptual)

flowchart LR
    A[Prepare Final Coat] --> B[Age at 27±2°C & 65±5% RH for ≥28 days]
    B --> C[Surface Ready for Testing]
    C --> D[Calibrate Gloss Meter]
    D --> E[Measure Gloss (Standard = 100 units)]
    E --> F{Gloss Value?}
    F -- Within 99-101 --> G[Test Valid]
    F -- Outside Range --> H[Recalibrate / Adjust]

Summary: Ensure proper aging, use calibrated gloss standards, and apply the test on the actual finished surface for valid results.

IS 5807 Part 5 - Reporting of Results (Clause 6)

• Report all individual readings: Record each measurement made along the grain and across the grain separately.
• Calculate mean values for each direction as per Clause 5.5.

Key Formula for Mean Value Calculation

[ \bar{X} = \frac{1}{n} \sum_{i=1}^{n} X_i ]

• ( \bar{X} ) = Mean value of readings
• ( n ) = Number of readings
• ( X_i ) = Individual reading

Specifications for Reporting

• Report individual readings and mean values for both directions.
• Use calibrated gloss standards (gloss = 100 units) as reference.
• Ensure agreement on test conditions between purchaser and seller (Clause 4.2).

Summary Table for Reporting

This ensures consistency and clarity in presenting gloss or surface finish test results.