How can I age a painting digitally to look old?

The simplest way to age a painting digitally is to use Age the picture in Easel by Zaweba. Instead of laying a brown filter over the image, it ages each material in its own way: oil and varnish yellow, fugitive colours fade, silverpoint tarnishes, newsprint browns and old oil cracks. Because the effect follows what you actually painted with, the result looks like time has passed rather than like a photo filter.

That is the key to a convincing old painting. Real ageing is uneven. A varnished oil portrait yellows overall, but the cheap red in the lips fades faster than the earth colours around it. A sketch on newsprint browns while one on good paper barely changes. Easel can do this because it knows what every mark is made of.

What ages and how

Oil paint and varnish yellow over the years, which is why old portraits look warm and golden even when the painter used cool colours. In Easel, a picture painted in oil or finished with varnish takes on that warmth.

Fugitive colours are pigments that are not lightfast. Over time sunlight bleaches them, so some reds and pinks fade while sturdier colours stay strong. Ageing in Easel fades those first, which gives that slightly washed-out look of an old print or watercolour.

Silverpoint, a drawing made with a silver stylus, tarnishes from grey to a warm brown. Newsprint, being cheap paper, browns and yellows quickly. Old oil cracks into a fine web, the craquelure you see on museum paintings.

Ageing a picture from start to finish

Start with the right materials. If you want an old master look, paint in oil on canvas or a panel and add varnish when you've finished. For an old sketchbook page, draw in silverpoint or pencil, and for something like a yellowed scrap, try newsprint as the surface.

Paint the picture as normal. It helps to think about how a painter of the period would have worked, because the ageing reads best on a picture that suits it.

Save the painting first as a .zeasel file so you have the fresh version to come back to. Then use Age the picture and look at the result. Compare the two and decide which you prefer, or keep both.

Getting cracks that look right

Cracking in oil is not random. Painters follow the rule of fat over lean: each layer should have a little more oil than the one below. If lean paint dries over fat, it cracks. Easel's mediums include linseed oil, glazing medium and solvent, and lean paint dried over fat cracks just as it would on canvas. So if you want craquelure in a particular area, paint that passage in a fat layer and lay a lean one over it. If you want a smooth area, keep the order right.

This is a good way to learn the rule too. Breaking it on purpose in Easel shows you exactly what happens, without ruining a real painting.

Exporting the aged picture

When you're happy, export as PNG, JPEG or TIFF at 1x or 2x, with or without the impasto lighting. Leaving the lighting on keeps the thick paint ridges visible, which suits an old oil. For a flatter, scanned look, turn it off. If you want to carry on with layers and masks afterwards, Edit in Paint by Zaweba sends a PNG straight over.

A few cautions

Ageing is easy to overdo. A little yellowing and a few cracks often look more believable than heavy browning everywhere. And if you are making a picture in an old style for fun, keep it as that: a homage, clearly your own work, not a copy passed off as old.

Used with care, Age the picture in Easel by Zaweba gives a warm, lived-in look that a simple sepia filter never quite manages.