Hello oldsalt-ga,
Maintaining appropriate humidity levels is very important to the
conservation of your French antique furniture. High humidity levels
can result in swelling, mold growth, softening of glues and
accelerated corrosion of metals. Low humidity levels can dry and
weaken furniture joints, shrink flat wood surfaces, splitting,
cracking, warping, gaps in joints and embrittlement of adhesives.
Most of the information that I found describes a range of relative
humidity levels that is best for the conservation of antique
furniture, as well as recommended temperature levels.
Generally, a safe humidity range appears to be 35% to 65%. The best
temperature range appears to be 68 to 75 degrees Fahrenheit. It is
also recommended that furniture be kept out of direct sunlight.
According to The Regional Alliance for Preservation (RAP),
(http://www.rap-arcc.org/leaflets/pifurn.htm) :
“To decrease excessive dryness during the heating season, keep rooms
with antique furniture cool and use a humidifier to add moisture to
the air – for most furniture, maintain a relative humidity of 35%.
Conversely, the summer’s humidity can also damage furniture. Long
periods of high humidity (above 60% relative humidity) can accelerate
the growth of molds and may encourage wood beetle activity. It can
also expand wood, placing added pressure on furniture glues and
joints. To avoid these conditions, use de-humidifiers; and small fans
can help circulate air and create a more even environment.”
According to the Florida Division of Historical Resources
(http://dhr.dos.state.fl.us/museum/ACS2/):
“To preserve your objects, you should control the humidity level in
your home, keeping it within the accepted RH range of 35% to 65%. If
necessary, supplement standard air conditioning with a humidifier or
dehumidifier.”
Regarding temperature, they go on to say:
“While not as damaging by itself as relative humidity, temperature can
accelerate chemical degradative reactions within a material. For
example, corrosion in a brass mount will proceed much more rapidly at
90 degrees and 50% RH than at 70 degrees and 50% RH. Elevated
temperatures also can cause loss of volatile plasticizers in a finish,
leading to embrittlement and cracking.”
The Henry Ford Museum & Greenfield Village website
(http://www.hfmgv.org/research/cis/furniture.html) states the
following:
“While precise control of temperature and humidity is desirable, it is
not always practical in homes. Therefore, damage should be minimized
by avoiding extremes in temperature and humidity. This can be done by
insuring that furniture is kept away from heat sources such as furnace
vents, fire places, warm lights and direct sunlight.
The recommended temperature and humidity levels for the storage and
display of furniture are as follows:
WINTER - Temperature 70 degrees F
Relative humidity 35%-45%
SUMMER - Temperature 70-75 degrees F
Relative humidity 55%-65%
Inexpensive humidity sensors can be purchased from conservation
suppliers.”
The Association of Art and Antique Dealers
(http://www.lapada.co.uk/care/furniture.html) gives a more precise
recommendation:
“The ideal humidity level is around 50 to 55 per cent and this can be
checked with humidity indicator cards, strips or a garden hygrometer.
The room temperature should be kept as constant as possible, with
central heating left on low at night. Rooms should be kept well
aired.”
This range is also recommended by The British Antique Furniture
Restorers' Association,
(http://www.air-improvement.co.uk/articles/bafra.htm ), The Air
Improvement Centre website):
“Prevention is always better than cure. It is possible to safeguard
antique furniture from dry air damage by investing in a good
humidifier which will help maintain a constant level of relative
humidity in the air during winter heating. Simply placing a bowl of
water or a pot plant near a piece of antique furniture is of little
value in protecting it from the effects of central heating. For a
normal comfortable indoor temperature of 70ºF, aim to maintain 50-55%
relative humidity.”
Specifically addressing French antique furniture, Sparrows Inc., a
U.S. importer of French antique furniture
(http://www.sparrows.com/care.htm), states the following:
“Most of the furniture we sell was crafted in France, which has a very
humid climate. In addition, central heating did not become widespread
there until late in the 20th century. For these reasons, our furniture
is accustomed to higher levels of relative humidity than are common in
American homes. During the heating season especially, indoor humidity
may drop low enough (10-30%) to dry out and weaken furniture joints or
shrink flat wood surfaces, resulting in splitting, cracking or
warping.”
They go on to say:
“There are several possible courses of action to maintain adequate
relative humidity during the heating season. Authorities recommend a
minimum relative humidity level of 45% at temperatures of 68—72
degrees Fahrenheit. To achieve this, you might consider placing open
pans of water near heating units or selecting, installing and using
any of a variety of humidifiers on the market.”
I didn’t find any references to unique care required for furniture
manufactured during particular time periods.
Other relevant references:
Resource, The Council for Museums, Archives and Libraries,
“Conservation of Furniture”, By Ian Fraser, Peter Winsor and Stephen
Ball
http://www.resource.gov.uk/information/advice/conserv07.asp
The British Antique Furniture Restorers' Association, “The Care of
Antique Furniture”, by John W. L. Kitchen MBE, Retired Head of
Conservation, Furniture and Woodwork at The Victoria and Albert Museum
http://www.bafra.org.uk/antique.htm
French Line Antiques, “Helps You Caring For Antique French Furniture”
http://www.frenchlineny.com/index3.htm
French Quarters Antiques, “Caring For Antique Furniture”
http://www.french-quarters.com/history/care.html
G D Blay Antiques, “Care And Maintenance”
http://www.gdblayantiques.com/care.htm
Brighton-Pittsford Post, “Humidity, 'Feeding' and Finding Antiques”,
November 15, 2002
http://www.mpnewspapers.com/nypacollector/features/286614497117663.php
Furniture Care and Conservation, by Robert F. McGiffin
Publisher: Amer Assn for State & Local; (October 6, 1995)
http://www.amazon.com/exec/obidos/tg/detail/-/0942063228/104-4843040-1178308?v=glance&s=books
Smithsonian Center for Materials Research and Education, Furniture
Conservation Training Program, Master Reading List
http://www.si.edu/scmre/fctp/fctpgsdc.htm
I hope you have found this information helpful. If you have any
questions, please request clarification prior to rating the answer.
Best of luck with your furniture.
Googlenut
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