Achieving this with the murky X-rays of the Goya is a bigger challenge, as the researchers did not already have an idea of what the painting underneath should look like. Instead, they mixed up X-rays of other paintings to see if the algorithm could learn to separate them. In this case, the algorithm is known as a "black box", meaning it may produce good results but it is not always clear how. To try and understand this better, the team looked at outputs from different points in the learning process and experimented with how feeding the machine data in different ways might improve the output.
