Gail,
I have always preferred to glaze our paintings when they travel for several reasons. Obviously, it protects them from being touched at a loan location you may not be familiar with, even though you read and believe everything written in their facilities report. As a conservator, I am interested in minimizing vibration during transport especially for paintings on canvas. I believe that gazing the painting with acrylic helps to dampen vibrations, especially if the painting is also backed with a sheet of inert foam attached to the backing board that just touches the back of the canvas. However, few curators like to view a painting through the traditional acrylic sheet material because of the glare it produces. Therefore, we used to allow the borrowing site to remove the acrylic for exhibit (if they requested to do so) so long as they replaced it before shipping it back to our museum.  
 
About two years, everything changed with the creation of Optium Acrylic. This is a very good non-glare acrylic sheet material. When properly lit with normal gallery track lighting, the Optium nearly disappears, even up close. Used in a historic house setting such as a room with some table lamps at eye level, some points of light are reflected by the Optium, but they are not disturbing and one can usually find a viewing point that eliminates them. Another advantage is that the microclimate created around the painting between the glazing and the backing helps to stabilize humidity changes, even without silica gel. Going a step further, a tightly controlled enclosure can be created by "encapsulating" the painting by covering the backing-board with Marvelseal extending around the edges of the painting and taped to the front edges of the Optium, inserting Artsorb behind the backing-board before the enclosure is sealed. 
 
We now glaze all our paintings before they travel and require the borrowing institution to purchase the Optium Acrylic as one of the conditions for loan. None have requested to remove the Optium and the paintings look terrific on exhibit. Another benefit is that we are slowly securing Optium for some of our most important paintings that we can choose to use in our own museum buildings to further protect our paintings from pointing fingers, environmental fluctuations, dust and pollution, and vandalism.  Cost is around $35/sq foot plus $20 for boxing and $25 for shipping.
 
No, I do not own stock in the Optium company and they are not paying me anything. I just like their product. For distributors, Google "Optium glazing."
 
Richard L. Kerschner
Director of Preservation and Conservation
Shelburne Museum
PO Box 10, Route 7
Shelburne, VT   05482
(802) 985-3348 x3361
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