What we know about the painting is that it was made in 1618 and the woman portrayed was 36-years-old at that time.
We don’t know exaclty what chemicals Mould used, although turpentine is usually mixed along with other solvents to remove varnish.
Historians and chemists usually collaborate in order to examine the kind of varnish and what chemical should be used to remove it successfully.
They will use test patches to see if their combination of chemicals is working and if so they will start the restoration process.
It is quite hard to find a good restorer. Based on the previous disasters, where restorers destroyed paintings of incalculable value and importance, people are now more cautious when it come to restoring a painting. They will think about it a lot more than they would in the past.