Page 21 - August 2018

Temperature and Relative Humidity
Extreme temperatures and high humidity contribute
signifi cantly to the breakdown of paper and other materials,
so keeping a constant environment in your building is crucial
for preserving historic documents, books, and photographs.
Heat greatly speeds up deterioration with each increase in
temperature of 18° F approximately doubling the rate of most
harmful chemical reactions. Relative humidity is the relation
of moisture in the air to temperature. High relative humidity
causes chemical changes to paper. In combination with high
temperature, humidity encourages mold growth and insect
activity on all types of materials. These high levels of humidity
and temperature also soften gelatin emulsions in photographs,
causing them to stick to other surfaces. Extremely low relative
humidity, which can occur in centrally heated buildings
during the winter months, causes certain types of paper and
books to become brittle. It can also cause emulsion layers on
photographs to crack or peel.
Frequent small changes in temperature and relative humidity
are even more damaging than constant extremes. Because
paper and books easily absorb and release moisture, they
expand and contract in response to daily and seasonal changes
Figure 2. You might have a ledger book like this one from the 1860s in in temperature and humidity. These changes accelerate
your collection. Photograph courtesy of David Bohl.
deterioration, causing paper or parchment to wrinkle, ink to
All of the following preservation techniques will help fl ake, emulsion to crack or separate from the base layers on
slow down the natural processes of deterioration in paper, photographs, and book covers to warp.
ink, photographs, and books. The best temperature for storing materials is between 65° F,
and 70° F and the best relative humidity is between 30% and
ENVIRONMENT 50%. A combination thermometer and hygrometer measures
Where and how you store your Masonic lodge documents, both temperature and relative humidity accurately, and can
photographs, and books can greatly aff ect how long they be purchased inexpensively at Sears or Brookstone. Climate
will survive. This section will help you understand how control equipment as simple as a room air conditioner, a
light, temperature, and humidity can aff ect these collections humidifi er, or a dehumidifi er can help maintain a constant
and what you can do to keep the environment stable and temperature and relative humidity, slowing the deterioration of
moderate. materials considerably. Buildings should be well maintained,
Light and cracks that allow water leaks should be sealed as soon as
Exposure to light, even for a short time, is damaging. This they appear. Doors and windows should be weather stripped
and kept closed at all times.
deterioration is cumulative and irreversible— that is, once
a document has faded, it cannot be restored, and further STORAGE ENCLOSURES
exposure to light will fade it more. For this reason, items in Proper storage can increase the life of Masonic documents
your collection should not be exhibited for more than three and photographs. When planning storage, you should consider
to four months. Light also weakens paper, making it brittle, the size, shape, and composition of the items. Then purchase
or it can cause the paper to bleach, yellow, or darken. boxes, folders, and shelving made of appropriate materials.
Light also causes inks to fade or change color, making Enclosures for Documents and Photographs
the documents and books diffi cult to read. It can also fade To ensure they last a long time, you should store your
bookbindings. Exposure to light can discolor photographs, rare and valuable Masonic lodge charters, certifi cates, and
especially color prints. photographs in protective boxes, folders, and envelopes.
Although all types of light are damaging, invisible These storage enclosures should provide physical support
ultraviolet (UV) radiation is especially harmful to for documents and photographs. Items should be stored
documents, photographs, and books. Sunlight and artifi cial individually or in small groups, and the size and shape of each
fl uorescent light emit high levels of UV energy, so they folder or envelope should match the item in it (see Figure 3).
are the most destructive. Ideally historic documents, Boxes should be able to close properly.
photographs, and books should be exposed to light only Some storage enclosures are made of materials that can
while they are being used. When not in use. They should actually damage the historic lodge documents and photographs
be stored in a windowless room that is lighted with they are intended to protect, so you must choose your boxes,
incandescent bulbs. If your storage area has windows, you folders, envelopes, and sleeves carefully. You may be surprised
should cover them with drapes, shades, blinds, or shutters
that completely block the sun. These simple changes to
your storage area can keep the items in it from fading. Continued Page 30.
Volume 94 Number 6 Montana Freemason Page 21