Climate and Textile Storage

The use of acid-free corrugated cardboard boxes and acid-free tissue paper have been found to be an effective means to protect antique textiles against inadvertent exposure to light, abrasion, and soiling. The isolation of textiles in this manner can also reduce the spread of an insect infestation while simultaneously mitigating against fluctuations in temperature and relative humidity. The Smithsonian Institution museums try to maintain their collections at 45% RH + 8% RH and 70o F + 4o F. This is not always possible, but the procedures to interleave and to separate individual textiles with acid-free tissue, to roll on acid-free tubes, and to pack in acid-free boxes has reduced damage enormously to textile collections in the Northern part of the United States.
However, the United States is divided into different climatic zones by gardeners and by building engineers.  The stability of textile collection also requires some considerations as to climate - and hazards.  These geographical hazards are not entirely controlled by environmental measures and certain traditional precautions based on climate are advised. Textiles have susceptibilities due to climatic conditions. The proper storage for a textile collection must consider the outside climate where the collection is located and the ease of retrieval!
Deserts
Dusty - even sooty interiors, whether due to an urban setting or to a wood-burning rural one, indicate the need for a protective covering.  Washable cotton sheeting (a fine percale count) trap dust before it reaches the antique textile; this is preferable to plastic or paper which transfer dust to the textile.  Technically, low humidity, desert conditions will make natural fibers more brittle.  If this low humidity is combined with intense sunlight and ultraviolet light, natural fibers will also degrade faster than in a more Northern exposure.
Cool, Humid Climates
... are conducive to mildew growth.  When warm humid air meet cold surfaces like window panes, the condensation of water from the air occurs.  Some hygroscopic surfaces like fabrics may dampen enough to support microbial activity.  Some interior areas are more likely than others to be affected: bathrooms, unsealed basement crawl spaces, unheated attics.  Exterior walls are more susceptible to these problems than interior walls.  In fact, a musty odor or evidence of mold or mildew may indicate a structural shortcoming of the home or building: problems with wall, inadequate moisture barriers or insulations, and/or problems with the roofing or gutters (drainage).
For nominal or non-structural problems, an increase in air circulation coupled with an increase in temperature will reduce the relative humidity in a closed interior space.  However, textile storage in such a climate should avoid closets or furniture chests placed in a susceptible location.  Compacted fabrics, like rolled carpets, should be unrolled, inspected, and removed to a drier location if necessary.  Overpacked, cramped conditions may promote damage to collection of uninspected textiles.  More air circulation and more air relative to the number of textiles per drawer is beneficial to the stability of the fabrics.
Because wool and hair fibers (cashmere, angora, mohair, and alpaca) are worn more in a cooler climate, dust in the home will be laden with wool lint.  Wool-eating insects can live on such lint, and prefer high humidities.  House cleaning (vacuuming) and clothes brushing are important.  If these garments are not seasonally stored with insect repellent (i.e. if they are worn in the summer), the drawers or shelves should be cleaned (wet wiped and dried).  Volatile scents (like cloves) used elsewhere as microbial deterrents for cottons or linens will not affect wool-eating insects; any scent will be less effective at lower temperatures.
Tropical (Warm Humid) Climates
... are conducive to insect growth.  Cockroaches actually find corrugations in cardboard attractive; silverfish and booklice eat the starchy components of paper.  Isolating fabrics in boxes can create microclimates, damper inside the box than the air outside it.
Reducing food sources or potential sites for infestation becomes more important the further south - or warmer the climate.  Excess paper and cardboard should be avoided.  Repellents may be used to deter insects and mildew.  Traditional methods include the use of vetiver (found in the US in some scented soaps), black pepper, and cloves.  These are used in various forms as sachets (i.e. not direct contact but as aerial scents) to protect cottons in the tropics.  Wool textiles are protected by paradichlorobenzene (PDB) fumes.  However, this chemical may be injurious to health.  Wool carpets and other woolens should be sealed hermetically to isolate the PDB odors, as well as the textiles.
One major open-air national museum in the tropics has successfully stored its textile collection for a century in tin-chests made of galvanized metal.  In the rural United States similar construction is found with metal footlockers or oversized popcorn canisters. Just as they keep foods from going stale, these tin-chests are proof against insect entry and do not absorb excess moisture.  Of course, such a storage system would be hazardous where condensation is a problem.
Cool Summers, Cold Winters
This sort of climate found in the north-eastern United States and in the upper mid-western United States, has been studied most extensively by museum conservators and scientists.  Most museum oriented textile storage methods and materials were designed for such a climate, once the interior spaces are protected by humidified heat and air-conditioning.  Textiles and costumes are most often interleaved or rolled with acid-free tissue paper and placed in acid-free boxes to protect against abrasion, handling, light, and dust.  The papers and boxes act as a humidity buffer during dry winters.  Insect attack may be isolated by boxing; prolonged periods of below freezing weather reduce the external insect population that might pressure interior spaces.  Microbial problems are deterred by the mild summers or by remedial air-conditioning which can reduce relative humidity inside such buildings.  Such storage does not, however, mean that insect damage to soiled woolens or neglected carpets will not occur.  Complacency - the tendency to forego house keeping (vacuuming, wipe-down cleaning) - may lead to irreparable damage despite a neat appearance.  Annual or semi-annual examination is a requisite and happy requirement to safeguard heirloom textiles in this climate as much as in any other.

 

USDA Plant Hardiness Zone Map

 

Range of average annual minimum temperatures for each zone

Zone 2 -50° to -40° F
Zone 3 -40° to -30° F
Zone 4 -30° to -20° F
Zone 5 -20° to -10° F
Zone 6 -10° to 0° F
Zone 7 0° to 10° F
Zone 8 10° to 20° F
Zone 9 20° to 30° F
Zone 10 30° to 40° F
Zone 11 above 40° F

References:
Ballard, M. “Climate & Conservation,” Book of papers, Textiles Specialty Group, American Institute for Conservation, 1992.

Lstiburek, J. and J. Carmody Moisture Control Handbook john Wiley & Sons, 1994.

Mecklenburg, M.”Determining the Acceptable Ranges of Relative Humidity And Temperature in Museums and Galleries: Part 1, Structural Response to Relative Humidityhttp://www.smithsonian.org/mci/english/learn_more/publications/reports.html
Mecklenburg, M. “Determining the Acceptable Ranges of Relative Humidity
And Temperature in Museums and Galleries: Part 2, Structural Response to Temperature
,” http://www.smithsonian.org/mci/english/learn_more/publications/reports.html

Mecklengburg, M. and C. Tumosa, “Resolving the Conflict between Building Preservation and the Proper Temperature and Relative Humidity Requirements of Collections,” 2003 http://www.smithsonian.org/mci/english/learn_more/publications/reports.html

Updated: July 2009