What is a glaze in painting?

A glaze is a thin, transparent or semi-transparent layer of paint applied over a dry underlayer. Light passes through the glaze, hits the layer below, and reflects back through the glaze — creating a luminous, jewel-like depth that cannot be achieved with opaque paint.

How many glaze layers do Old Master paintings use?

Old Master oil paintings typically used 3 to 15 or more glaze layers, built over weeks or months. The dead colour (grisaille) underpainting was overlaid with successive transparent colour glazes. The final surface could be 10–20 thin layers deep.

Why does a white ground produce more luminosity?

A white ground reflects maximum light back through the glazes. Each photon passes through the glaze layers twice — once going in and once returning — doubling the colour-modifying effect. Dark grounds absorb light rather than reflecting it, producing rich but less luminous results.

What is the difference between a glaze and a scumble?

A glaze is a transparent dark colour applied over a lighter layer. A scumble is an opaque or semi-opaque light colour applied over a darker layer. Both build optical depth but through opposite mechanisms. This calculator handles both: low opacity values are glazes, higher values approximate scumbling.

How do I calculate glaze opacity?

Mix a small amount of paint into a clear medium and brush it across a strip of black and white card. The opacity is how much the underlying card shows through. Many pigments are naturally transparent (e.g. alizarin crimson, phthalo blue) while others are opaque (titanium white, cadmium yellow).

ArtCalcs

Glaze Layer Calculator — Cumulative Opacity & Depth

Calculate cumulative opacity, light transmittance and optical depth for transparent glaze layers in oil, acrylic, watercolour and gouache.

Opacity Per Layer

Transparency of each individual glaze layer (1 = very transparent, 50 = semi-opaque)

Number of Layers

How many glaze layers you intend to apply

Paint MediumYour primary painting medium

Ground / Base ColourThe colour of your painted or primed ground

How We Calculate This

The calculator treats each glaze layer as a multiplicative transmittance filter:

Formulas

Transmittance per layer = 1 − (opacity / 100)
Total transmittance = Transmittance per layer raised to the power of the number of layers
Cumulative opacity = 1 − Total transmittance
Layers for coverage = log(0.05) ÷ log(Transmittance per layer)

The advanced options add a refractive index modifier for optical depth estimation, a layer drying factor for medium-specific transmittance adjustment, and a dilution ratio to account for paint-to-medium mixing.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always verify quantities before purchasing materials.