Cleaning a “Giant”

  • Posted by: Maggie Bearden
  • Posted Date: January 6, 2014
  • Filed Under: Conservation

CleaningBlog1    How to remove unoriginal varnish and overpaint from a 17th-century oil painting?  Step 1: Obtain a graduate degree in art conservation; Step 2: Carefully perform cleaning tests using a range of organic solvents, gel systems, and aqueous methods; Step 3: Choose a system that can be safely administered without causing harm to the underlying original paint layers.

The removal of degraded coatings and discolored overpaint has long been a  controversial topic in the history of restoration.  Today, conservators have access to a wide range of materials and solvents and are equipped with a substantial background in chemistry.  Restorers of the past were limited by what they had access too, which unfortunately included the use of harsh chemicals and concentrated acids and bases (such as lye and ammonia).  Modern professionals have access to a wide range of materials and solvents, and conservators are armed with a substantial background in chemistry.

cleaning blog2     Concepts such as pH, conductivity, and solubility are always taken into consideration during testing.  Problematic pigments and other components can also be sensitive to different cleaning procedures.  So PLEASE think twice before grabbing your bottle of Windex® when you are thinking about cleaning a painting!!

The cleaning process has really involved two major steps, removal of the yellow varnish followed by the removal/reduction of discolored overpaint.  Blues, whites, and lighter tones tend to suffer the most dramatically when covered with a thick, yellow veil of varnish as demonstrated in Figure 1.  Below the varnish, the conservators also encountered multiple layers of restoration “glazes” that had been hastily applied across the entire surface.  Several other figures had been treated in a similar manner during previous restoration campaigns, notably the standing solider on the left side ofthe painting.  In Figure 2, it is possible to get a sense of how broadly the overpaint had been applied; in many areas the original drapery pattern and the folds of the cloak were entirely hidden or poorly misinterpreted by past restorers.

While some areas possessed large amounts of varnish and overpaint, others simply suffered from blanched varnish.  “Blanching” occurs when the varnish has become significantly degraded and no longer exists as a continuous film.  Microscopic air pockets begin to form within the film and between the varnish and the paint.  This makes it difficult to read the paint beneath as the varnish is no longer effectively saturating the surface.  Conservators decided to leave small areas of the blanched varnish intact for students, scholars, and visitors to get a sense of how degraded the varnish had become (see Figure 3).   By December, the conservation team had been able to successfully clean the bottom half of the painting, moving onto the top half after the New Year.CleaningBlog3


  1. Comment by Emily W. — January 10, 2014 @ 12:40 pm

    It’s really cool how you made your images superimposing the detail shot on top of a more overall view of where it is in the painting. FYI the “graduate degree” link appears to be broken.

    Hope you guys are having fun!

  2. Comment by Andrew Not Warhola — January 23, 2015 @ 11:34 am

    I occasionally buy thrift shop oil paintings, and just to see what would happen, I DID use Windex® on two of the less than $10 paintings I have. In the long run, there may be damage, but for something to hang that looks nice, it worked just fine. I sprayed them down thoroughly with Windex® let them sit for just a few minutes and sprayed them again with warm water, as a rinse. I gently patted off any excess water. Amazingly, the surface dirt, which is probably mostly nicotine stains, immediately dripped off. They look OK to me, and I looked at them through one of my camera lenses.

    Again, I did this to two no-name artist’s oil paintings, I would never do that to anything of great value. But I did it just to see the results.

    Yes, I am that person that when you tell them not to do something, that defies all logic and does it. Sometimes with disastrous results, and sometimes wonderful results. This time the results seemed good.

  3. Comment by Kristin de Ghetaldi — June 15, 2015 @ 9:24 am

    Hi Andrew,
    Glad to hear that this worked out for you. I happened to have recently finished a long and lengthy job for a private client for whom this was NOT successful. Perhaps better safe than sorry with things of value….as was the case with the Cortona painting no doubt!

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Last Modified: January 6, 2014