Dec 3, 2021 - by https://www.papermilldirect.co.uk/inspire/what-is-greyboard-and-what-is-it-used-for

Greyboard is made from 100% recycled materials and can be used in many craft construction projects to add extra strength and rigidity. This sturdy greyboard gives your craft constructions a stronger feel, either used as backing card or a protective outer layer

What is Greyboard Used for?

Mounting

Greyboard is ideal to be used as a backing for paintings and prints. The sternness of the mount board will help to protect paintings and prints from creases and folds. Our Greyboard offers the perfect mounting size for large prints, and our Greyboard is ideal for those smaller  prints.

Box Making

Due to the stiffness of the Greyboard it is the perfect material to use when created boxes as it helps to construct a solid structure. if you have heavier items that will be going into the box you can choose a thicker greyboard to ensure they wont cause damage to the box and are kept safe.

Model Making

As Greyboard has a high level of stiffness it is the perfect material to be used in model making. It is easy to cut using a sharp scalpel or a heavy-duty craft knife making it very versatile for your model making needs.

The thickness of Greyboard is measured in microns. 1000 Microns = 1mm, so the higher the value, the thicker the card or paper.