Optical properties

General informations

Optical properties such as brightness, opacity and gloss can be measured using the equipment at the Physical Testing Laboratory.

The main product groups tested are:

• raw materials such as paper, tissue paper, folding boxboard, composites, etc.
• finished products such as folding boxboard, books, brochures, tissue products, blister packaging, labels, flexible packaging, envelope windows, etc.

Technical Data and Achievements

The following optical properties can be measured according to the standards listed below:

Brightness and CIE whiteness

• ISO brightness of papers and boards, according to ISO 2470-1
• D65 brightness of papers and boards, according to ISO 2470-2
• Brightness of pulverized clay and other mineral pigments, made into uniformly compacted pigment plaques according to TAPPI method T 534
• Brightness of pulps after preparation of laboratory sheets, according to ISO 3688 and ISO 2470-1 or ISO 2470-2
• Brightness and colour of tissue paper and tissue products, according to NF EN ISO 12625-7 (D65/10°) and 12625-15 (C/2°)
• CIE whiteness (D65/10°) of papers and boards, according to NF ISO 11 475
  
• CIE whiteness (C/2°) of papers and boards, according to ISO 11476.

Color

• Measurement of the colour (parameters L*, a*, b*) according to ISO 5631-1, or ISO 5631-2, or ISO 5631-3, depending on the chosen illuminant.

Opacity

• Opacity (paper backing), according to NF ISO 2471
• Opacity (white backing) according to NF Q 03-006
• Opacity of tissue paper and tissue products, according to NF EN ISO 12625-16

Measurements of brightness and colour can also be made using instruments with a variety of geometries:

• on a D/8° instrument, with a small measuring surface area.
  
• an instrument with 45°/0° geometry

Transparency

• Determination of transmittance by diffuse reflectance measurement, NF ISO 22891
• Haze transparency according to NFT54-111 or ASTM D 1003

Gloss

• Gloss, according to NF EN ISO 8254-1, measurement at 75°.
  
• Gloss, measurements at 20°, 60° and 85°

Other measurements can also be made. A few examples are:

• Optical density by reflectance or transmission
• Presence of fluorescent whitening agents by visual observation under UV light
• Presence of security features in banknote paper
• Presence and counting of fluorescent fibres.

Measurement of whiteness		L*, a*, b* colour space