GemDiagram Docs

What is Frosting

Frosting is a surface finish that grinds away a thin, delicate edge along each facet, leaving the facet centres polished. It's a real cutting technique used to create a subtle matte look at seams, softening the sharp reflections that would otherwise flash brightly at the facet boundaries. In GemDiagram, frosting is applied computationally — the 3D model shows frosted edges, and the cutting report and PDF export include them.

How frosting works

When you frost a facet, GemDiagram adds a series of thin frost facets — nearly invisible slivers sitting along the seams where the main polished facets meet. These slivers are:

  • Thin: Typically 12–16% of a main facet's area, hugging just the edges.
  • Rotated: Each sliver's plane is rotated slightly (about 2.5°) about the seam direction, tilting the edge shallower than the main facet.
  • Roughened: The slivers have a light surface roughness that scatters light, creating a soft, frosted appearance instead of a sharp flash.

The result is that light hitting the edge refracts through the frosted sliver instead of bouncing straight back — it's optically subtle but visually softens the stone.

Frosted vs. polished

In the 3D viewport:

  • Polished facets (the norm) are smooth and shiny — they reflect light in sharp, specific directions.
  • Frosted facets look slightly grainy or matte, scattering light diffusely. In Realistic render mode, you'll see the difference clearly; in Solid mode, frosted areas appear as a rough gray finish.

Single-facet frosting vs. whole-side frosting

You can frost individual facets one at a time (see Click-to-frost a facet), or you can frost an entire side (pavilion or crown) at once using the Add Frosted Facets dialog (see Add Frosted Facets).

Both approaches apply the exact same frosting geometry — the difference is just how you select which facets get frosted.

Why frost a stone?

Frosting is mainly used for aesthetic reasons:

  • Softens the look: Reduces sharp sparkle and creates a more subtle, refined appearance.
  • Hides asymmetries: If a cut has slight angle variations, frosting can hide the resulting asymmetric flashes.
  • Matches a design intent: Some famous cuts (like certain step cuts or vintage designs) are traditionally frosted on the pavilion; frosting is part of their signature look.

It's optional — a polished stone will always sparkle more brightly, but a frosted stone can look more elegant. The choice depends on your design vision.