Gortzius Geldorp, Portrait Of A Member Of The Sani Family (1582)

19th-Century Works

Industrial processes resulted in smoother grounds, which are more uniform and even. This tends to lead to minimal pitting or texture.

Pigment Behaviour

Pigments themselves also age in characteristic ways. 

Older Works, Pre 1800

The use of lead white can result in transitions, which feel soft and velvety. While umber and ochre create a sense of warmth, which is hard to replicate with machines. If the artist applied thin glazes, these can ‘sink’ into the early grounds, which produces a sense of textural depth.

Pieter Bout & Adriaen Frans Boudewyns, Extensive Rhineland Landscape With Sportsmen (c. 1675)

19th-Century Works

Generally, later works exhibit a smoother quality via machine-milled pigments. The paint will feel more manufactured and the transitions in colour tend to be flatter.

William Shayer & Edward Charles Williams, Travellers Outside An Inn (1850)

Collector's Tip: Various pigments age in unique ways; for example, Vermilion can blacken, and Smalt is prone to fading. So always consider pigment behaviour in the context of the whole painting.

Varnish

As varnish ages, it undergoes transformations. Older varnishes may present with a warm amber cast with uneven yellowing in the recesses. You might also spot tiny pockets of oxidation. While later varnishes are more even with a less dramatic colour shift. From personal experience, it’s usually simpler to remove newer varnishes during conservation. We’ve handled paintings with up to 16 layers - applied across the centuries.

Overpaint

During the 19th century, restorers approached most works with a rather liberal attitude. One gets the sense that they aimed to ‘improve’ upon a painting with their nous. We understand, today, that this is never a good thing, and often conservators are unpicking the overzealous work of the past. 

You can spot overpaint, particularly if it’s sitting on top of the previous craquelure. E.g. think of it like archaeology, whereby if the cracking extends under the paint, it’s later overpaint. For older works, at times, you’ll see overpaint that’s also carrying age and, as such, it also bears craquelure. But the cracking here should be a little different.

Other ways to spot overpaint include:

• Examine the painting with a good UV torch, as it may fluoresce, unless hidden under varnish.
• Note any unusual changes in colour temperature. Older overpaint may discolour over time.
• If you’re handling a portrait, do the eyes and/or the lips appear a little modern? It might be the victim of Victorian ‘beautification’. Perhaps the entire head feels unnaturally smooth?

All older works have generally been retouched at some point, and it’s not always detrimental to their value. It just needs to be handled sensitively.

Support: Dating Canvas & Wood

Both canvas and wood supports can reveal plenty about the age of painting, particularly when you consider the reverse in conjunction with the painted surface. Older works on wood are hand-planed, with irregular tool marks. 

Late 16th-Century Catalan School, Saint Magí & Saint Mauro (c. 1580)

While on 19th-century panels, you’ll spot regular joins and machine-sawn timber. For canvases, as you would imagine, the older ones are handmade and usually rather coarse with uneven weaves. Newer, machine-made canvases are consistent, tighter, and have a fairly linear weave.

Summary

The list above is far from exhaustive, but hopefully assists in your quest for the truth. Combined with art historical research, provenance, and consideration of the subject matter, the surface of a painting can yield many clues to verify or question its age. 

And one final note: One must always act as one's own devil’s advocate to avoid the all too human issue of ‘confirmation bias’. This, in turn, will hopefully reduce the volume of inaccurate attributions, which currently plague our industry. Good luck!