ASTM D523
Standard Test Method for Specular Gloss
Measures specular gloss of nonmetallic surfaces using 20-degree, 60-degree, or 85-degree geometries.
What ASTM D523 specifies
ASTM D523 measures reflected light with a glossmeter at one of three geometries. The 60-degree geometry is the general-purpose measurement. The 20-degree geometry provides better discrimination for high-gloss surfaces, while the 85-degree geometry provides better discrimination for low-gloss surfaces. Results are reported in gloss units relative to the instrument standard and are not percentages. Surface texture, color, film thickness, curvature, cleanliness, and measurement direction can affect readings. A finish requirement should state the angle, target or range, specimen location, and any directional measurement rule rather than saying only matte or glossy.
ASTM D523 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Requirement / test |
|---|---|---|
20° geometry | Geometry used for improved discrimination of high-gloss surfaces, typically selected after a high 60° reading | Gloss units at 20° |
60° geometry | General-purpose geometry used across the middle gloss range | Gloss units at 60° |
85° geometry | Geometry used for improved discrimination of low-gloss surfaces, typically selected after a low 60° reading | Gloss units at 85° |
Tests and the drawing call-out
Tests the document imposes
- 20-degree specular gloss
- 60-degree specular gloss
- 85-degree specular gloss
How to cite it
Drawing call-out
SPECULAR GLOSS PER ASTM D523: <TARGET OR RANGE> GU AT <20|60|85>°Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
ASTM D523 — frequently asked
Which ASTM D523 angle should be used?
Use 60° for general measurement, 20° for better high-gloss discrimination, and 85° for better low-gloss discrimination.
Are gloss units percentages?
No. Gloss units are instrument values relative to a calibrated reference standard.
Why must a drawing state the gloss angle?
The same surface gives different values at different geometries, so a gloss number without its angle is incomplete.
ASTM D523 is copyrighted by ASTM International. This page explains the document so a drawing can be read; it does not reproduce the standard. Purchase the current edition from the publisher. Official source ↗