Humidification chambers

Pippa Cruickshank <pcruickshank [at] thebritishmuseum__ac__uk>
writes

>We are looking to replace our walk-in humidification chamber for use
>in the treatment of organic materials. ...

Although the walk-in unit in my paper conservation laboratory does
not have temperature control and may be far more humble than what
The British Museum envisions, I have had great success with a space
that was constructed over a week-end with off-the-shelf lumber,
heavy polyethylene sheeting, PVC tubing, and silicone caulk.  While
recognizing that every laboratory is built differently and that any
walk-in unit has to be customized accordingly, I offer the following
general description of the chamber that I use to humidify paper and
parchment objects and consolidate paint.  Perhaps this concept can
be of use to other readers of the DistList.

The unit is 8 feet high x 3 feet deep x 5 feet wide, built into a
niche of that size at one corner of the laboratory.  A simple wood
frame was assembled to give shape and support to the chamber, then
one piece of polyethylene was laid between the fibrous ceiling tiles
and the metal grid that supports them, and a second sheet of
polyethylene was cut to form all four sides of the chamber including
extra height and width so the large open side can drape onto the
floor and extend about 1.5 feet beyond the side of the entry corner.
A third piece of polyethylene covers the carpet-covered portion of
the floor.  All joints were sealed with silicone caulk and/or the
plastic-adhesive strips sold to seal joints around bath tubs and
showers.  Wood lath was screwed along the edges of each plane to
keep the sheeting from sagging.   One vertical edge was not sealed
and can be opened wide so objects, easel, table, tools, and
conservator can be arranged as needed.

While objects are humidifying, the chamber is sealed by pushing a
board of floor-to-ceiling height against the lab wall, about 1.5
feet beyond the unsealed edge.  Foam tape along the edges of the
board compensate for any irregularities in the wall surface and
prevent the board from cutting the polyethylene sheet.  The bottom
of the closing side is sealed by draping the sheet outward and
laying snake weights across the bottom of the entry side.

Humidity can be introduced in two ways.  An inexpensive ultrasonic
humidifier stands inside the chamber, its electrical cord extending
out of the chamber and into an adjacent plug. (Before purchasing an
ultrasonic humidifier, verify that it does not have a sensor that
stops humidity generation when a certain r..h. has been reached in
the immediate area.)  With that one unit, the chamber can reach 80%
RH. in less than an hour--the exact length of time varying with the
setting used on the humidifier.  A PVC tubing port built into the
lower far corner of the entry side allows introduction of more
humidity from a unit placed just outside the chamber.  A small
hygrothermograph attached to one of the wood laths inside the
chamber allows the conservator to monitor conditions.

Lighting comes from two sources: one of the smaller walls is in
front of a floor-to-ceiling window, and artificial light from the
lab comes through the large entry side of the chamber.

Christine Smith
Conservation of Art on Paper, Inc.
2805 Mount Vernon Avenue
Alexandria, Virginia 22301
USA
703-836-7757


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                  Conservation DistList Instance 18:53
                  Distributed: Saturday, May 14, 2005
                       Message Id: cdl-18-53-004
                                  ***