Ultrasonic mister for consolidating paintings

Inger Grimstad <ingergrimstad [at] yahoo__com> writes

>I have read a few articles by Michalski and Dignard etc. (CCI) about
>the ultrasonic mister (UM) with great interest!  In theory I think
>the method sounds perfect for consolidation of matte paint, but I
>get the impression the method is not very widely used, and I wonder
>why? If anybody has had bad experiences (or good for that matter)
>with the method, I would be grateful to hear about it!

I have not used the ultrasonic mister yet on object treatments but I
have experimented with both the mister and a disposable nebulizer in
our lab.  I was very pleased with the preliminary results and would
definitely consider using the mister set-up on a future object
treatment.  I believe that this technique may not be more widespread
due to the time it takes to acquire all the supplies needed (e.g.
tubing and nozzles) and, possibly, the time required to set up the
equipment each time for use.  I found that the initial set up was
tricky and the mister was somewhat finicky but the problems were
outweighed by the good results that the technique produced.

Michalski and Dignard in their 1997 article point out several
disadvantages to the ultrasonic mister for consolidation.  First,
"viscous solutions cannot be misted" (p.111) and, second, "not all
solvents work well: solutions in water, ethanol, or mineral spirits
do, but some solutions in fast-evaporating solvents such as acetone
do not" (p.111).  A 1993 article on the "Consolidation of Porous
Paint in a Vapor-Saturated Atmosphere" by E. Hansen, R. Lowinger
and E. Sadoff gives useful background information on the evaporation
time and rates of several solvents.

>From my admittedly limited experience I found that even using the
mister with a B-72 in ethanol solution was trickier than working
with water based solutions.  I found that the ethanol solution
stopped misting and the problem only seemed to be fixed when I used
a fresh batch of consolidant. This indicated to me that the ethanol
had evaporated to a point where the solution was too viscous to
mist.  I thought that this happened surprisingly quickly suggesting
that a solvent like acetone would certainly be unsuitable.

The success of the technique relies on multiple applications (e.g.
4-10) of very dilute consolidant concentrations.  This might be the
main draw back for using this method for your Munch paintings.  The
method was quite time consuming and I would think to consolidate the
entire surface of a very large painting could take an extremely long
time.  If the surface only required localized treatment the
technique might be more appropriate.

Rachael Perkins Arenstein
Assistant Conservator
Department of Anthropology
American Museum of Natural History
Central Park West at 79th Street
New York, NY  10024
212-769-5447
Fax: 212-769-5334

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                  Conservation DistList Instance 13:28
                 Distributed: Tuesday, November 2, 1999
                       Message Id: cdl-13-28-004
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