You heard of the Mona Lisa?

You probably haven't heard of Lisa Del Jack Condo, whose portrait some scientists think was painted over in making the Mona Lisa Pablo Picasso apparently painted over someone else's portrait to create his work.

The Old guitarist.

Same thing for Vincent van Gogh in painting Patch of Grass.

One thing these findings all have in common.

They were discovered decades or centuries later using modern scientific instruments.

Here's how some researchers solve or find historic mysteries of art.

A painting would change for the moment it's made, and so that there's no chance of restoring it to the way it looked when it was first made.

But you can appreciate how it might have looked I doing the research that's needed and then presented in the best way it could be presented with these new tools.

It's become a little bit easier to find out more about painting techniques and to find out in more detail about materials.

For example, use a handheld X ray fluorescence spectrometer to look at areas of a painting and look up the kind of elements they contain.

We learned a lot from people X ray pictures and X rays will penetrate all the way through the painting so you can see aspects of the whole thickness of a picture.

Sometimes you can see the frame and the nails that have been used to hammer the canvas in.

You can see reworkings in pain so you can see things that you can't see on the surface.

There were different devices that used for infrared photography, so you can do on it.

Frieda Photo and especially adapted camera.

You might see something beneath the varnish you might see drawing underneath the paint layer so you might find a picture under another picture or drawing underneath the picture that's been covered up with a completely different picture.

There are always new discoveries to be made.

Each of these techniques tells you something different.

To make you a good conservative.

I think you need all those elements.

Eventually, you know, everything changes and everything deteriorates.

Although we now use materials which we hope will last at least 100 years.

Inevitably, pictures will need to be cared for, and those those works have been cared for now way retain that way, benefit from that we can still see them and the things that have been very neglected with we've lost them.