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Subject: CAL/NCPTT environmental conference

CAL/NCPTT environmental conference

From: Charles S. Tumosa <cst>
Date: Friday, January 9, 1998
In September 1997, the Conservation Analytical Laboratory of the
Smithsonian and the National Center for Preservation Technology and
Training sponsored the "Symposium: New Guidelines for Collections
Environments". Summaries of this conference appeared in NCPTT Notes
(Nov 1997) and elsewhere. The undersigned felt that the "findings"
presented required comment. The following note was submitted to the
NCPTT for inclusion in an upcoming issue of NCPTT Notes. They
refused to publish it. We felt that this information should be
disseminated. The note that follows is as submitted to NCPTT.
Unfortunately, the figure cannot be reproduced here.

    About New Guidelines for the Museum Environment

    The November article, "Towards new guidelines for collections
    environments", reported the "findings" of an invitation only
    conference, "Symposium: New Guidelines for Collections
    Environments". The "findings" require comment. We were not
    invited to the conference but our work was discussed and
    interpreted by the attendees. Significant differences of opinion
    exist among the attendees, us, and others who were not invited.

    The "findings" state that one must determine and quantify the
    risks posed to the collection by environmental settings and
    fluctuations. Unfortunately, there was no mention of, or
    reference to, any means to do so. It is easy to talk about "risk
    management" but *not* easy to determine the nature and
    significance of the risks. Very specific recommendations for
    environmental settings abound, but are rarely based on solid
    evidence. Early recommendations included tight control of
    environmental fluctuations simply because no one knew how much
    variation was safe. The often specified +5% RH was acknowledged
    by Thomson to be "based more on what we can reasonably expect
    the equipment to do than on any deep knowledge of the effect of
    small variations on the exhibit." [1, p.114] That fact has been
    forgotten or ignored. Acceptable RH and temperature fluctuations
    can now be quantified [2].

    The last three "findings" are the most problematic.

    The symposium guidelines state "A well-controlled environment
    with humidity fluctuations of plus-or-minus five percent is
    considered the safest environment". Why? No solid data or
    evidence supports this narrow range and ample evidence permits
    wider tolerances. Anecdotes or appeals to personal expertise are
    not suitable for setting guidelines. Cycling within a moderate
    RH range (such as 35 to 60% RH) has no permanent effect on the
    physical stability of objects [2]. Objects have survived quite
    well for hundreds of years in "uncontrolled" environments when
    extreme changes (such as severe dryness caused by central
    heating) were avoided. Tight RH tolerances do not necessarily
    improve chemical stability, either. Reducing both temperature
    and humidity (within a safe range) increases chemical stability.
    Cycling to cooler and drier conditions during winter can be
    significantly better for the collection even though exceeding
    the typical +2F and +5%RH range. This can be true even if the
    environment is slightly warmer and more humid in the summer!
    Carefully planned seasonal cycling is *not* a concession to
    energy costs that may compromise the safety of the object, but
    rather an improvement in the overall strategy of preventive
    conservation. Controlled cycling has fundamental benefits. It is
    a myth that any cycling compromises the safety of collections
    and that avoidance of cycling is always ideal. Tighter
    tolerances do not necessarily guarantee a "safer" environment.

    Other factors must be considered [2], even at 70F and 50% RH.
    Objects such as diseased bronze or salt infested ceramics are
    exceptions to a 50% RH setpoint (as well as the range 35 to 60%

    A report on the symposium stated that the participants "thought
    that a well-controlled environment within standards now
    generally used (70 degrees Fahrenheit and relative humidity at
    50 percent, plus or minus 5 percent) was the preferred choice
    when possible" [3]. If one "flatlines" despite the costs and
    problems, these "standard" setpoints of 70F and 50% RH are not
    optimal. No data or research supports these values. For
    instance, 68F and 40% RH is chemically and mechanically better
    for virtually all museum objects, and is still within the range
    of human comfort.

    The preoccupation with a "flatlined" environment and arbitrary
    setpoints discourages collections managers from taking modest
    steps to upgrade the environment. If taken seriously, the
    avoidance of cycling would make it impossible to transport most
    objects, to put objects into cool or cold storage or to remove
    objects that are already in it! Both experimental evidence and
    practical experience, for example, show that appropriate cold
    storage conditions are better than the general museum
    environment for photographic collections, despite the "cycling"
    of removal for exhibition or study. Photographs can be subjected
    to such cycling safely and with no damage [4].

    The "finding" that relaxation of the "usual" standards will not
    likely lead to great cost savings is false. Millions of people
    set their home thermostats back in winter to save energy. The
    Ayres study [5], which is often cited and misinterpreted as
    supporting this "finding", only considers differing tolerances
    around constant setpoints, i.e. flatlined environments. The
    study has no relevance to environments in which the SETPOINTS
    are changed or allowed to drift within a safe range. Seasonally
    changing temperature and RH setpoints result in the greatest
    savings. Other design aspects of the study also preclude its
    usefulness in the present discussion.

    Theoretical, experimental, and practical evidence prove that
    seasonal setpoints save substantial amounts in construction,
    maintenance, and energy costs. Museums themselves provide the
    best evidence. A midwest museum maintained 50% RH throughout the
    year and sustained $3,000,000 in damage caused by condensation
    in the winter. In 1978, Thomson cited an "extra 14% on the basic
    structural cost solely for humidification to 50%" [1, p. 113].
    Estimates for the proposed National Air and Space Museum annex
    show millions of dollars in increased construction costs for a
    "flatlined" building. Less rigid tolerances also allow one to
    use simpler, more reliable environmental control systems.

    The figure shows energy costs for Smithsonian buildings (as well
    as for a private home) versus the yearly RH range. The tightness
    of environmental control, not the type of construction or
    efficiency of HVAC systems, is the primary factor determining
    cost. In fact, the newer, "more efficient" buildings designed to
    be "flatlined" are the most costly! The same trends are found in
    the book "Museums Environment Energy" edited by May Cassar, and
    in data from other institutions. A museum in the midwest
    constructed an addition and upgraded its HVAC system to
    "flatline" the environment. The museum increased its size by
    30%. Its energy costs more than doubled. Another museum was
    doubled in size and upgraded to "flatline". The energy costs
    quadrupled! The new additions and new equipment were more
    "energy efficient". One can hardly claim that "relaxing the
    usual standards will not likely lead to great cost savings."
    Money and effort wasted on inappropriate environmental control
    would be much better spent on other aspects of collections
    management and preservation.

    The conference did not achieve its goal of clarifying the issue
    of guidelines for collections environments.

    For further information, we may be contacted by phone at
    301-238-3700 ext.118, by e-mail at CST [at] CAL__SI__EDU or by regular
    mail at Smithsonian Institution, CAL/MSC MRC534, Washington DC


    1.  The Museum Environment, G. Thomson, 1978, Butterworths,

    2.  "The Determination of Appropriate Museum Environments", D.
    Erhardt, M. F. Mecklenburg, C. S. Tumosa, and M.
    McCormick-Goodhart, in The Interface Between Science and
    Conservation, British Museum Occasional Paper Number 116, S.
    Bradley, ed., 1997, The British Museum, 153-163. Also references

    3.  "Research Vistas", D. O'Connor, Smithsonian Institution
    Research Reports, 90 (Autumn 1997), 2.

    4.  "The Allowable Temperature and Relative Humidity Range for
    the Safe Use and Storage of Photographic Materials", M. H.
    McCormick-Goodhart, Journal of the Society of Archivists, 17(1)
    (1996), 7-21.

    5.  "Energy Conservation and Climate Control in Museums, A Cost
    Simulation under Various Outdoor Climates", J. M. Ayres, J.
    Druzik, J. C. Haiad, H. Lau, and S. Weintraub, The International
    Journal of Museum Management and Curatorship, 8 (1989), 299-312.

        [Figure. Energy costs as a function of RH control for the
        Washington, DC area Smithsonian museum complex. Data for the
        year 1993.]

Charles S. Tumosa
Marion F. Mecklenburg
David Erhardt Mark H.

                  Conservation DistList Instance 11:59
                  Distributed: Friday, January 9, 1998
                       Message Id: cdl-11-59-001
Received on Friday, 9 January, 1998

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