Borosilicates: How They’re Made

9th June 2020

At the core of every particle of Moonshine Effect Pigment, lies a borosilicate flake. Glass, referred to as borosilicate in effect pigments is all around us, so how is it produced into flakes? The quality of these flakes is what differentiates Moonshine from so many other pigments – so how are they made?

Firstly, it is important to understand quite why so much emphasis is placed on what is on the inside of the pigments. You might even think that as a pigment, that only the outer layer is important. As a difference to typical absorption pigments, Moonshine effect pigments work on the interference effect, involving the entire pigment particle. You can see this difference below between our Effect Series and Meta Effect Series pigments. To give a consistent colour and effect, the borosilicate substrate must be of a consistent thickness and highly planar. A low refractive index is also key to give a difference between the substrate and metal oxide.

Morphology

Our borosilicate substrate is manufactured using a unique rotary method, carried out exclusively in the UK with Glassflake Ltd. The rotary method using centripetal force to produce very fine borosilicate flakes of extremely tight consistency. For most pigments, this means a tolerance of  ±150 nanometres. When the metal oxide layer can be as thin as 80 nanometres, any large inconsistencies could completely change the visual effect. A much thinner substrate is used in production of the market leading Astral Effect Series. This has a nominal thickness of 350 nanometres, with an even tighter average tolerance of ±50 nanometres. You can read more about the benefits of this thinner substrate HERE.

Composition and Heavy Metals

Beyond the morphology of the flakes, the composition is also critical. Borosilicate is melted from the constituent metal oxides, which provides total control over the final composition. Close monitoring of this step gives excellent oversight of the final composition to control thermal and chemical resistance (crucial in pigment manufacturing), as well as visual effects such as refractive index and transparency.

The composition and choice of metal oxide components is key to ensure the purity of the final pigment. Metal oxides can frequently contain traces of heavy metal impurity so it is important to select high quality starting materials. This coupled with extensive testing of pigments by ICP-OES ensures that all grades meet regulatory requirements

Joshua Hayes
Business Development & Marketing Manager

Business Development Manager for Glassflake Ltd, since 2017. Coverage of Europe and The Americas in all key markets of coatings, composites and inks. Special interest in Additive Manufacturing.