Efflorescence on oil paintings

Here's an interesting question I received from a retailer, about oil
paintings and efflorescence.  I talked to the manufacturer of the
paint, so I know that a paper was published about 1997 regarding the
problem.  I also got a solution from the manufacturer, but not a
clear answer as to why the problem occurs. It seems to happen
without regard to weather, geography, brand, local environmental
conditions, and so on.  Here is the question, sanitized to protect
the identity of all the players:

   "Are you aware of any significant efflorescence problems starting
    to occur with oil paintings[?]  We have two customers with
    significant problems.  They are [name of manufacturer] users.
    [The manufacturer is] aware of the problem and says it isn't
    necessarily brand specific and is happening around the country.
    I'd like another sources input, i.e., yours.  I'd be happy to
    call you on my dime if you have the time."

According to the manufacturer, this occurs with thickly painted oil
paints with little or no medium.  It will not happen if the paints
are thinly applied, with a medium, and are varnished.  The solution:
wipe the painting off with a minimum of odorless mineral spirits,
and oil out using a thin painting medium (alkyd or oil). Let the
medium sit for about 30 seconds, then wipe it off.  The
efflorescence should not reappear.

Any thoughts from the assembled experts?  We would appreciate your
help.

Mark D. Gottsegen
Chair, ASTM D01.57
Associate Professor
Department of Art
UNC Greensboro
1203 NC 62 East
Climax NC 27233-9183
336-707-3647
Fax: 336-334-5270
mdgottsegen [at] earthlink__net
<URL:http://www.thepaintershandbook.org>


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                  Conservation DistList Instance 20:1
                  Distributed: Saturday, June 24, 2006
                        Message Id: cdl-20-1-006
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