High Shine and Easter Bunnies: What is the Flop Index?

What better time to talk about flop than Easter, when we’d like an excuse to put an Easter Bunny on our blog.

Easter bunnies and the Flop Index

We’ve been celebrating the Xerox Iridesse Production Press a lot lately, and something that is oft-quoted is that it produces output with a ‘high flop index’. But what does that actually mean?

Depending on the angle at which a colour is viewed, whether a painted or printed surface or otherwise, the colour might change. Think, for example, about metallic-coloured cars, which can appear very differently when viewed from different angles, or where the bodywork curves.

If you look at a colour ‘normally’ you see the ‘face’ colour. However, if you look at it at an angle, you see the ‘flop’ colour. Should you have a piece of metal, for example, as you tilt it, the colour ‘flops’ and you see different shades. Without going into too much technical detail, a ‘lightness flop’ (lustre/shine) and ‘colour flop’ are both attributes of metallic materials. 

David H. Alman derived a flop index as follows in order to calculate a value for F:

F = 2.69 (L*15 – L*110)1.11/ (L*45)0.86

For more information on this please see this scholarly article

The higher the value of F, the greater the effect. In other words, the higher the flop index result, the higher the change in reflectance of a metallic colour as it is rotated through various viewing angles.

Were a colour to look the same from all angles, then the value of F would be 0. But were it to change substantially, a high value might come in at 15 plus.

The new formulation of Xerox’s Speciality Metallic Dry Inks, with flat metallic flakes embedded in the toner particles, boosts its Flop Index to high levels without the need for traditional foil stamping. The Iridesse boasts industry-leading small-particle HD EA toner formulations that enable even transfer of up to six layers of toner link. This results in beautiful image quality - with added sparkle.

So now you know!

Happy Easter from all at First Copy.

Elizabeth Budd