Transparent vs Opaque Colours in Oils and Acrylics

A misunderstanding I regularly encounter in workshops is what is meant by “transparent” in a paint colour. It seems to come from conflating “see-through” and “colourless” into “transparent”.

We can see through some things that have colour. Think of stained glass or coloured cellophane or sunglasses. You see through it, though it adds colour to what’s behind it, changes the colours of things seen through it. Normal window glass is colourless; stained glass is transparent (to varying degrees, but that’s a digression).

If you’ve done a workshop with me, you’ve probably seen this “visual aid”. One day I’ll create a neater, textbook version!

At the bottom right of that sheet is a black line with opaque, semi-opaque, and transparent colours painted over it.

Pigments Transparent vs Opaque

How opaque or transparent a pigment is depends on the inherent properties of a pigment, but also how thickly you use it. Red iron oxide is one of the most opaque pigments there is, even more than titanium white. It obliterates whatever’s beneath it.

Figuring out which colours are which is best done by creating a chart of your own. Yes, many tube labels give an indication, but you can’t beat trying it for yourself, straight from the tube and thinned somewhat, as well as adding white to transparent pigments to shift their opacity.

It’s an excuse to get out every tube of paint you’ve got and say hello to it. Neatly in a grid or not, that’s a potential procrastination. Just put brush into paint onto paper and save neatly for another day.

Also: Transparent Watercolour Doesn’t Mean Colourless Paint

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