Hegman Gauge
Grindometer
Fineness of Grind Gauge
Precision Hegman Gauge
Precision Grindometer
Precision Fineness of Grind Gauge
Expert Dispersion Quality Assessment
ASTM D333 ASTM D1210 ASTM D1316
ISO 1524 DIN 53203 DIN EN 21524
BS 3900-C6 FTMS 141a 4411.1
PR NF T30-046 AS/NZS 1580.204.1

Fineness of Grind Gauge QPI-HG - Standard Test Application:

This test application description details the technical procedure for determining the degree of dispersion and particle fineness of liquid coating systems—such as paints, inks, and slurries—using the QPI-HG (Single/Dual Channel) and QPI-HG (Wide Channel) Fineness of Grind Gauges. The test follows the foundational principles set forth in ASTM D1210 (Standard Test Method for Fineness of Dispersion of Pigment-Vehicle Systems by Hegman-Type Gauge) and ISO 1524 (Paints, varnishes and printing inks — Determination of fineness of grind).

1. Equipment & Working Principle

• QPI-HG Series Block: Precision-ground stainless steel block featuring one or two parallel channels machined with a continuous, uniform taper from a specified maximum depth (e.g., 100 µm) down to zero depth (0 µm).

• Scraper Blade: Double-edged steel blade ground to optical flatness, designed to pull a uniform drawdown film across the block surface without bowing.

• Scale Conversions: Readings are evaluated in micrometers (µm), Hegman units (0–8), or PCU (North Standard scale).

2. Standard Test Procedure

Step 1: Preparation & Surface Cleaning

1. Ensure the QPI-HG gauge block and scraper are completely clean, dry, and free of dried resin, solvent residue, or surface scratches.

2. Place the block horizontally on a level, non-slip workbench in a bright, well-illuminated area.

Step 2: Sample Application

1. Mix the liquid test sample thoroughly to ensure a representative, bubble-free dispersion.

2. Apply a generous pool of sample into the deep end (100 um mark) of each channel, ensuring enough volume to fill the entire groove volume during the draw.

Step 3: Drawdown Execution

1. Hold the scraper perpendicular to the block surface (at a 90-degree vertical angle relative to the plane) using both hands.

2. Apply firm, uniform downward pressure and pull the scraper smoothly along the gauge from the deep end to the zero end in a continuous motion lasting approximately 1 to 2 seconds.

Step 4: Immediate Visual Assessment

1. Read the gauge within 5 to 10 seconds of completing the drawdown to prevent surface evaporation or film skinning.

2. View the wet film at a low angle (20 to 30 degrees) against a direct light source to clearly highlight surface specks and scratches.

3. Reading & Rating Criteria

ASTM D1210 Rating

• Observe the point along the scale where the liquid film first displays a continuous band of prominent specks or a noticeable break in surface smoothness ("peppered" appearance). Isolated individual scratches at the deepest end are ignored.

• Record the value at this boundary in Hegman units (0–8) or micrometers (µm).

ISO 1524 Rating

• Identify the level where a high density of particles breaks through the film surface across a width of 3 mm to 5 mm in the channel.

• Express the result in micrometers (µm) corresponding to the depth marked on the side scale.

4. Calibration & Care Notes

• Cleaning: Wipe the block and scraper immediately after each test using a soft lint-free cloth saturated with an appropriate cleaning solvent. Never use abrasive pads or metal tools.

• Storage: Coat clean surfaces with a light film of anti-corrosion oil and store inside the protective wooden case when not in use.

• Inspection: Periodically inspect the scraper edge for nicks or wear using an optical comparator, as edge roundedness will distort depth readings.