In the 20th century it was discovered that if you use infrared technology, wavelengths of light slightly longer than normal light, you can see through the paint and magically reveal the drawings that are underneath. This kind of drawing we refer to as underdrawing. It’s never supposed to be seen in the final version of the painting; it will always be covered by paint. But with this technology we can see through the paint and see whether there’s an underdrawing there and if there is, what it can tell us about how the artist was working. Infrared reflectography is particularly good at revealing things that are painted in black. This gives quite a complicated image to study, which shows you a mixture of anywhere that black is in the whole painting, from things like Arnolfini’s black hat which is painted with carbon black, so that shows in the infrared. But in places like his purple robe and almost the whole of the rest of the picture, the light has been able to go through the paint, and has revealed to us underneath the first marks that van Eyck put down in a liquid material with a brush, but a linear drawing of what he was going to paint. Jan van Eyck always does some kind of an underdrawing under his paintings. But the level of detail in the underdrawing for the Arnolfini is extraordinary. To have done this exquisite amount of final precision with the drawing, only to cover it all up with paint, is extremely unusual. Unexpectedly, in a picture that looks as though as it’s so completely finished, we found some very significant changes where what he has drawn is completely different to what he ended up painting. Probably the most important one is the right hand of Arnolfini, which in the painting is sideways on to the viewer. But if we look here in the infrared you can see a hand drawn with its palm out, facing us. Then there are some parts of the painting which were never underdrawn at all. The most fun one of those is if we look at the little dog; the little dog has no underdrawing at all. The only reason that we can see in the infrared that he’s there is that black paint was used for his eyes and his nose. They show in the infrared. But that’s not underneath the paint, that’s the surface paint showing. When you are looking at infrareds of paintings, it can be a huge thrill that you’re the first person to see something that was last seen by Jan van Eyck. And sometimes it really does make you feel as though you’re getting much closer. You can understand how the artist was thinking, but know this painting is always going to remain an enigma.