ISO 7668

Introducing ISO 7668 – Industrial Physics

ISO 7668 is an ISO international testing method that will help you to measure the specular reflectance and specular gloss of anodized aluminum and its alloys. 

So, before we explore what’s involved in this ISO gloss testing and reflectance testing approach, let’s define the key terms you’ll need to know:  

• Specular reflectance: the ratio of the luminous flux, reflected in the specular direction for a specified source and receptor angle, to the luminous flux of the incident light, normally expressed as a percentage. 
• Specular gloss: the ratio of the luminous flux, reflected from an object in the specular direction for a specified source and receptor angle, to the luminous flux reflected from glass with a refractive index of 1,567 in the specular direction. 

ISO 7668 testing – what’s included? 

This is an ISO test designed specifically for specular gloss testing and specular reflectance testing of anodic oxidation coatings at angles of 20°, 45°, 60° or 85°. 

The ISO 7668 test methods are intended mainly for use with clear anodized surfaces. They can also be effective with color-anodized aluminum, but only with similar colors. 

Specular reflectance and specular gloss are not unique physical properties of a surface. Both vary with the angle of measurement. They’re also affected by aperture dimensions that define the incident and the reflected beams.  

The specular reflectance of most surfaces increases with the angle of measurement. This is why reflectometers of various angles are used when testing painted surfaces. The specular reflectance characteristics of anodized aluminum don’t always behave in an expected manner. Plus, due to its double reflection properties, reflected light comes partly from the film surface and partly from the underlying metal.  

With all this in mind, it’s advisable to measure the specular reflectance characteristics at 20°, 45°, 60° and 85° for a more complete understanding. We will happily talk you through which method(s) are the most relevant in any particular situation. As an example – the specular reflectance of bright-anodized aluminum, with a mirror finish, is best measured using 45° or 20° geometry. 

ISO 7668 gloss testing apparatus

You’ll need a few pieces of gloss testing apparatus in order to carry out a successful ISO 7668 test and these include:  

Polychromatic light source and housing: with a lens that directs a parallel, or very slightly converging, beam of light onto the surface under test. 

Receptor housing: containing a lens, a receptor aperture and a photoelectric cell, to receive the cone of reflected light. 

Sensitivity control: for setting the photocell current to any desired value on the instrument scale or digital indicator. 

Receptor meter: capable of giving an indication proportional to the light flux passing the receptor aperture, within one percent of the full-scale reading.  

ISO 7668 gloss testing and reflectance testing equipment

So, how can Industrial Physics improve your ISO 7668 gloss testing and reflectance testing? 

TQC Sheen Glossmeter – Sologloss & Polygloss
The TQC Sheen Glossmeter comes in two models. The Sologloss glossmeter measures 60° and the Polygloss glossmeter 20°/60°/85°. The 60º measuring angle can be used for any surface, from matte to glossy. For better gloss measurements on high gloss surfaces the 20° angle is available, while for low gloss surfaces the 85° angle suits best. 

Need ISO 7668 testing solutions? Get in touch

We’ve learnt a thing or two about gloss testing over the decades. Now Industrial Physics is recognized as a brand that likes to bring new ink and coatings testing equipment to market. 

Across the knowledgebase section of our website we like to share our expertise and publish lots of blogs on related subjects. For example, why not have a look at this piece which tells you how to interpret a gloss meter reading? Then you could follow up with this sustainability themed thought leadership piece which advises you not to gloss over simple sustainability wins! 

If you have any questions about ISO 7668 specular gloss resting and specular reflectance testing, or how we can help you, then please just get in touch!

Contact us – Industrial Physics

Your global test and measurement partner for ISO 7668