London ( CNN ) -- There are few people in the world lucky enough to form a close relationship with a Leonardo da Vinci painting . New York-based conservator Dianne Dwyer Modestini is one : She spent hundreds of hours lovingly restoring `` Salvator Mundi , '' da Vinci 's newly rediscovered painting of Christ . And , says Modestini , when she finally had to say goodbye to the painting it was like enduring a painful break-up . `` I 'm quite serious , '' she said . `` It was a very intense picture and I felt a whole slipstream of artistry and genius and some sort of otherworldliness that I 'll never experience again , '' she said . She describes suffering separation anxiety and depression over losing the painting , and with it her connection to the enigmatic painter who was its author . For art historians , the lengthy and emotional process of conserving a great masterwork is both a privilege and an overwhelming responsibility . `` People say , 'How can you touch it , it 's so scary , ' '' said Modestini , who is Senior Research Fellow and Paintings Conservator for the Samuel H. Kress Program at the Conservation Center of the Institute of Fine Arts , New York University . `` I was n't frightened of it in those ways -- that it 's one of 16 paintings , it 's worth x amount of dollars -- because I would have been paralyzed , I would n't be able to work like that , '' she continued . Of course , when Modestini started work in 2005 , she did n't know she was dealing with the first da Vinci painting to be discovered in over 100 years , worth , according to some estimates , around $ 200 million . The painting , now authenticated , revealed its identity little-by-little during the conservation treatment . Modestini started the process using solvents to clean off some of the murky varnish and over-paint that was concealing the painting 's true identity . Within just a few hours during her first session with it , she was able to see the work much more clearly . `` It 's very mysterious , the things that happen to paintings , '' she said of the over-paint job . `` People forget or they begin to doubt the original opinion of the person who originally said it was by Leonardo and particularly if it 's been badly repaired . They might not understand what 's underneath -- it happens to pictures all the time , '' she continued . The next step was to take the cracked painting apart and piece it back together again , a procedure that took about a year . `` It is quite a delicate process , '' said Modestini . `` It has to be very precise . '' Then , she had to make re-touches to the badly damaged areas , refining Christ 's eyes and lips . It was a particularly difficult and lengthy part of the process because , she said , she had `` to make the decision of what to touch and what to leave alone . '' `` I wanted ( to be sure ) that none of my restorations had impinged on the original , that I had not done too much , because old pictures have to look old -- if you take out every crack , every spot , every anomaly , they can easily look like a reproduction , '' she said . Larry Keith is the Director of Conservation at the National Gallery in London and responsible for the conservation of da Vinci 's `` The Virgin of the Rocks , '' which is in the gallery 's collection . This treatment involved cleaning off the layers of yellow , foggy varnish , applied in a previous restoration process , `` to allow the picture to saturate properly so you can see the full total range of thematic relationships that are there in the painting , '' said Keith . The process of cleaning this particular painting took 18 months , he said . It is is now on view at the National Gallery as part of the exhibition `` Leonardo da Vinci : Painter at the Court of Milan '' along with `` Salvator Mundi . '' He agrees that the job of conserving such a masterpiece is an honor few are lucky to have . `` It 's wonderful to see the picture in a different light and conditions and over the course of a treatment , you do get very close to a picture , '' he said . As to whether he felt close to Leonardo da Vinci while working on the painting , he said : `` I suppose you do , in as far as anyone can get close to Leonardo . '' `` There 's a certain mystery at the core of him I think , but it 's true , you 're in very close contact for a long time and it 's a very privileged role , '' he concluded .
Two recently restored paintings by Leonardo da Vinci on view at London 's National Gallery . To restore such a painting is a fraught privilege . Process requires time , care and attention to detail . Conservators develop strong bonds with paintings they restore .