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Subject: Bread


From: Paul Storch <paul.storch>
Date: Tuesday, April 24, 2001
Erin Quinn <quinne [at] ci__greeley__co__us> writes

>The interpreters at my site are asking whether they can make and
>display "museum" bread to give a more realistic feel in our historic
>houses.  They do not have a recipe for this, so I am not even sure
>what exactly we would be dealing with.  They tell me that you bake
>it like regular bread, but it is then coated with something to
>protect it from pest infestation.  I am hesitant to even proceed
>with it because I can't imagine the protective coating being good
>for being near  museum objects.  So, I am wondering if any of you
>have heard of "museum" bread, what the recipe might be and whether
>it is recommended for use in museums or not.

Erin Quinn inquired about the preparation of "museum bread" for
interpretive use.  I have prepared various types of breads, from
Finnish flat breads to matzos, with everything in between.  I've had
the best success with breads that are not glazed with eggs, as the
interior of the bread tends to shrink slightly away from the glazed
layer, causing delamination.  I agree with Nynne Carl's answer about
drying in a controlled oven, although I use a regular lab oven
adjusted to just below the boiling point of water to drive out the
moisture without re-baking the bread.  I monitor the drying process
by weighing the bread before drying, and at regular intervals
(usually 12 hours) during drying until the weight remains constant.
A one pound loaf usually takes about 3-4 days to dry completely.

Since our Education Department uses the breads for handling by
students, I have to strengthen the dough by resin impregnation in
order to make them last.  Breads that are on display may not require
this extra step.  I would argue that the concerns about "toxic
coatings" are irrelevant here, especially if the breads are prepared
by a conservator in a properly equipped lab.  I use vacuum
impregnation with Acryloid (Paraloid) B-72 in acetone to strengthen
the breads.  I've also experimented with Parylene coating, but the
results are similar and the B-72 method is much less expensive and
easier to do.  The main limitation is the size of the bread that can
be fit into the vacuum chamber and the vessel.  Once the
impregnation is complete, the bread is removed and dried in a fume
hood on a metal rack.  The used consolidant can be collected and
either re-used or disposed of properly.  Once the acetone has
evaporated, the breads do not smell, and there are no VOC's that
will harm objects if the bread is used in a display case.

If the above explanation is not clear or if you require further
information, please contact me off-list.  Thanks,

Paul S. Storch
Senior Objects Conservator/Section Head/Internal Unit Preparation
Daniels Objects Conservation Laboratory (DOCL)
B-109.1, Minnesota History Center
345 Kellogg Blvd. West
St. Paul, MN  55102-1906
Fax: 651-297-2967

                  Conservation DistList Instance 14:57
                  Distributed: Friday, April 27, 2001
                       Message Id: cdl-14-57-005
Received on Tuesday, 24 April, 2001

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