Glitter Colour Effects – Playing with the ‘Physics of Light’
Over the years ‘glitter myths’ have developed. In this blog we aim to bust the myth of what’s behind the glitter colour effects. I’m sad to say it’s not ‘magic’, but something far more magical, the physics of light.
Glitter effects can be grouped into three main groups; Metallic, Iridescent and Holographic. They all utilise different types of light physics in their creation:-
1 – Metallic Effect Glitters – Specular Reflection
Metallic glitters; silver, golds, reds, greens, blues etc. The effect is created by reflecting light. The glitter particles can be imagined as mini mirrors, each one reflecting light. Within the structure of the glitter is an extremely thin layer of aluminium, more than 200 times thinner than a human hair, with the sole purpose of reflecting light. Transparent colour coating are applied to either side of the glitter particle to give colour metallic effects.
Metallic glitters are opaque, ie they conceal anything underneath the glitter, as the aluminium layer blocks and reflects any light.
Bioglitter™ Product Ranges with Metallic Effect –
Bioglitter™ SPARKLE product ranges are metallic effect glitter and indistinguishable in appearance from traditional metallic effect plastic glitters.
2 – Opalescent and Iridescent Effect Glitters – Refraction & Reflection
Opalescent and iridescent glitters consist of effects where colour can only be seen when viewed from a particular angle or colour travel effects, where the colour observed changes depending upon which angle the glitter is viewed. Opalescent and Iridescent glitters utilise refraction and reflection light physics. In an iridescent glitter, light is refracted and in a way spun back on itself back. Iridescent glitters are created by micro layering more than one hundred alternate layers of two plastics with different, but complementary refractive indexes. The microlayer film is created by hi-tech extrusion of the two colourless synthetic plastic polymers. Iridescent glitters are transparent, unlike metallic and holographic which are opaque. Refractive index is the value given relating to a materials ability to bend light.
These types of plastic glitter do not contain any pigment or reflective aluminium and are completely transparent. The intensity of the iridescent effect is increased by using these types of glitters against a dark or black background.
The Structure of Plastic Iridescent Glitter
Bioglitter™ Product Ranges with Opalescent / Iridescent Effect –
Due to the physical properties and chemistry of the natural and plant derived raw materials used in Bioglitter™, it is not possible to re-create the structure of a plastic iridescent glitter (as illustrated above). Therefore, we have had to take a completely different approach. Bioglitter PURE is a completely new structure of glitter, unique to Ronald Britton Ltd. Like iridescent glitter, it does not contain aluminium, so it is transparent and the effect looks stronger against a dark or black background. However, unlike plastic iridescent glitter, Bioglitter PURE does not have a microlayer structure….. Bioglitter PURE is; opalescent, iridescent glitter reinvented.
Bioglitter™ PURE, consists of three colour ranges of increasing strength of effect. The first-generation, launched in 2019, is the ‘Natural’ colour range. In 2020 we launched stronger effects, consisting of the ‘Opal’ colour range, a mother of pearl or opalescent effect and the ‘Vivid’ colour range, a strong metallic effect with not as much iridescence.
All Bioglitter™ PURE products are aluminium free, ie they don’t rely on a metallised aluminium layer to produce their shine. Being aluminium free they offer the added benefit of providing extra resistance in applications where the aluminium layer in a metallic or holographic glitter would be attacked and eventually destroyed, such as in soaps and detergents.
Recreating the iridescent intensity without the ability to create a microlayer structure or have the choice of materials with varying refractive index presents a real challenge for us. However, with further development, we hope to offer future generations of Bioglitter™ PURE that become ever closer to the effects that are currently achieved with plastic iridescent glitters.
2 – Holographic Effect Glitters – Diffuse Reflection
Holographic glitters produce a rainbow effect creating by the diffuse reflection of light into its component colours. Just like a rainbow splits light into its component colours, each glitter particle acts as mini prism splitting light. The structure of a holographic glitter is similar to a metallic glitter in that it has a very thin aluminium layer to reflect, with the addition of a pattern to diffract the light.
Holographic glitters are opaque, ie they conceal anything underneath the glitter, as the aluminium layer blocks and reflects any light.
Bioglitter™ Product Ranges with Holographic Effect –
Bioglitter™ Holo is currently in development.