Sustainable Preservation Practices for Managing Storage Environments Series # 3 - Webinars

Equilibration and Enclosures June 10, 2015 Today’s Presenter • Jeremy Linden, Senior Preservation Environment Specialist, Image Permanence Institute

• Ably assisted by Christopher Cameron, Sustainable Preservation Specialist

Technical Support & Information

• Cable internet preferred rather than wireless or dial-up Need Help? • Participants can use their Contact Lauren computer’s speakers (VoIP) or Parish at telephone. [email protected] • United States Toll: +1 (951) 384-3421 or • Access Code: 598-778-692 585-475-7175 • Audio PIN: Shown after joining the webinar Questions?

Submit questions using the Question Box located in the Go To Webinar control panel. Sustainable Preservation Practices for Managing Storage Environments

• The third series of workshops & webinars • Funded by a National Endowment for the Humanities Education & Training Grant Sustainability Series Presentations are Designed To Provide: • A better understanding of how to balance the need to both preserve collections and reduce energy consumption

• Practical guidelines for managing/reducing any risk to collections that could result from new energy management practices Webinar 5 – Equilibration and Enclosures Today’s Focus: 1. A Few Definitions 2. Thermal & Moisture Equilibration Basics 3. The Basics of Equilibration Behavior 4. The Problem of Dryness and Dampness 5. The Risk to Materials 6. Equilibration and Enclosures – Research Results First, a few definitions… Equilibrium is a state of balance between opposing forces or actions that is either static or dynamic Equilibrium is reached when the material has fully equilibrated to the amount of heat or moisture in the environment Hygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment Hygroscopic materials (those that absorb moisture) experience equilibration as they adjust to the amount of heat and moisture Hygroscopic behavior of thin pine veneer – Institute for in the environment Advanced Architecture of Catalonia Thermal Equilibration Thermal Equilibration is the process of adjusting to the ambient temperature of the environment – materials make this adjustment from the periphery to the core

www.physicsclassroom.com Thermal Equilibration • Most materials adjust to the temperature of a new environment in a matter of hours • The time needed to adjust is influenced by the amount of exposed surface area and the thermal mass of the object – More exposed surface area → faster temperature equilibration – Greater thermal mass → more time to fully equilibrate Thermal Equilibration Studies Show: • It is the temperature level and NOT the temperature fluctuations that are most likely to cause damage – Higher temperatures → faster chemical reactions – Lower temperatures → slower chemical reactions

• Sustained high temperatures have the most significant impact on the stability of the collection materials, not temporary spikes or wide fluctuations in temperature Moisture Equilibration Moisture Equilibration is the process of adjusting to the ambient relative humidity of the air by absorbing or desorbing moisture Moisture Equilibration

• Most materials adjust to changes in RH in a matter of days or weeks • Moisture equilibration is influenced by more variables than thermal equilibration, including: • The hygroscopic nature of the material • Dimensional characteristics and the amount of surface exposure • Temperature also influences the rate of moisture equilibration Moisture Equilibration

• As relative humidity increases, hygroscopic materials absorb moisture from the environment • As relative humidity decreases, hygroscopic materials release (or desorb) moisture into the environment • Moisture equilibrium is reached when the moisture content (EMC) of the material is in balance with the relative humidity of the surrounding air Moisture Equilibration Studies Show:

• Wide and sustained fluctuations in RH increase the rate of mechanical decay

• Avoid prolonged periods of low or high RH – Low RH → Dryness → Increased risk of mechanical damage – High RH → Dampness → Increased risk of mechanical damage and mold growth Dryness • Dry conditions that threaten collection preservation occur in a variety of climates and seasons around the world – “Winter dryness” is common in northern US and Canada – Arid climates may mix normally warm, dry conditions with a “wet” season Dryness Dryness is simply a lack of moisture in the environment, and a function of two factors: – Low absolute humidity (dew point) – Low relative humidity Absolute Humidity / Dew Point • Dew Point temperature is a representation of the actual moisture content of air (absolute humidity) – When the dew point is high, more moisture is present – When the dew point is low, less moisture is present Relative Humidity • Relative Humidity is the percent saturation of air based on the current temperature and dew point • At a constant dew point, as temperature rises RH goes down / as temperature drops, the RH goes up

Preservation Impact of Dryness

• Chemical Decay: POSITIVE IMPACT – Reduction of moisture in the air (and the object) slows the rate of chemical degradation of organic materials and reduces the possibility of corrosion • Mechanical Damage: NEGATIVE IMPACT – Desiccation of collections materials can lead to tightening of joints, cracking of bindings, veneers, and paint layers, and loss of elasticity • Mold Risk: POSITIVE IMPACT • Mold spores won’t germinate in dry conditions Best Practice for Dry Conditions • Keep the environment dry, but not too dry • 30% RH minimum for most collections • 35-40% RH for sensitive materials • 20-30% RH is safe for inorganic material (stone, metal, ceramic) Dampness • Damp conditions that threaten collection preservation occur in a variety of climates and seasons around the world

• In the US, damp conditions are seasonal and regional Dampness • Damp conditions in storage spaces can result from: • Moist, humid outside air, precipitation, open water or ground water • Water leaks, condensate, surface or ground moisture Preservation Impact of Dampness

• Chemical Decay: NEGATIVE IMPACT • High levels of moisture in the air (and the object) increase both the rate of chemical degradation of organic materials and the potential for metal corrosion • Mechanical Damage: NEGATIVE IMPACT – Absorption of moisture by organic materials can lead to swelling, buckling, dye bleed, weakening of fibers • Mold Risk: NEGATIVE IMPACT – Risk of mold increases at 65% RH and above, biological activity increases Best Practices for Damp Conditions • Most damage can be avoided by keeping RH below 55% • Excursions above 65% should be limited to a few days to avoid mold • Be aware that lowering the temperature in a space will raise the RH if the dew point stays the same Summer Humidity Comparison Example: Historic House without forced ventilation -

27,000 cu. ft. air volume - Typically one air change per hour by infiltration

On a summer day, in humid On a summer day in dry Savannah, Georgia, 98 Henderson, Nevada, 1.1 gallons of water will infiltrate gallons of water will in the form of water vapor infiltrate in the form of water vapor

Materials at Risk

The level of risk to an object from dry and/or damp conditions is based on three characteristics: • Nature of the material • or history • Composition Nature of the Material • Hygroscopic materials – which absorb & release moisture • Primarily organic materials – items made from materials that were once living plants or animals - wood, paper, textile, leather, horn, bone, ivory, shell, parchment, etc. • Some inorganics – ceramics with soluable salts, oxidizable metals, calcareous materials, etc. Provenance / History • Materials have a memory • If originally created and housed in dry or damp conditions, objects are less likely to see damage from those continued conditions

Composition • Composite objects – Paintings, furniture, musical instruments • Solid wood or ivory objects – Carvings, statues, masks • Stretched hide or canvas – Drums, vellum-bound IPI Research on Equilibration and Enclosures • 1994-97 – Environment and Enclosures in • 1998-2001 – Effect of Fluctuating Environments on Library & Materials • 2010-14 – Effect of Setbacks in Temp & RH in Collection Environments • 2014-16 – A New Path to Sustainable RH Control Environment & Enclosures in Film Preservation - 1994 Focused on: • Effectiveness of different enclosure figurations • Rates of T and RH equilibration • Practical recommendations for preservation of cellulose acetate photographic film Effect of Fluctuating Temperature and RH on Chemical Decay - 1998

Findings: TEMPERATURE CYCLE PROFILE • Cycling temperature 50°C e r

and/or RH is u t a

r 35°C

not inherently e p m

detrimental e 20°C T • T and RH levels matter

1 Day Effect of Fluctuating Environment Full moisture equilibration takes time (data at 20 degrees C) Materials Enclosures 90% Equilibration

HC Book on shelf One month

35mm Film None Two weeks

35mm Film Metal can Six months

2” data tape Plastic Six months container Effect of T & RH Setbacks - 2010

• Methodologies for Sustainable HVAC Operation in Collection Environments

An investigation into the best methods to ensure that library, , and collections are not harmed by short-term environmental fluctuations made in the name of reducing energy costs and institutional carbon footprints.

T & RH Setback Research • How do you evaluate the impact of short-term fluctuations on collection preservation? • How far can the envelope of “safe” conditions be pushed before real damage is done?

• Intentional changes during unoccupied hours • HVAC shutdown • T and RH setbacks • Seasonal set points

Setback Project Elements

• Lab research on T & RH changes in micro-environments at the core of materials • Field investigation with RIT Libraries – short-term setbacks during unoccupied hours • Data analysis & development of a methodology for implementing sustainable HVAC operations Setbacks Laboratory Study: Test Samples • Sixteen configurations studied

Material Housing Book Book on shelf

Photos stack Cardboard box

Matted photos Cardboard box Portfolio box Museum case Paper stack Cardboard box Office metal cabinet Flat-file metal cabinet Profile Temp. RH One-week cycle Decrease at Constant RH adjusted accordingly Four cycles Dew Point

One-week cycle Increase at Constant RH adjusted accordingly Four cycles Dew Point

One-week cycle Decrease in sealed Passive control Four cycles space

One-week cycle Increase in sealed space Passive control Four cycles

Sustained levels over 4- Constant at 21°C 1st month: 30% week period 2nd month: 40% 3rd month: 50% 4th month: 60% Over Twenty Profiles 5th month: 70% 6th month: 80%

Typical Environmental Profile: Constant Dew Point Assembling and Monitoring Matted Photos in Cardboard Box: Temp. Change in Microenvironment Matted photos in Cardboard Box: RH Change in Microenvironment Thermal Equilibration: Enclosure Types

Ambient T Museum Case Cardboard Box Effect of Enclosures: Micro-RH Micro-RH versus Material Core What Did We Learn? . Temp increase at the material surface: . First causes “short-term” desorption . Then moisture diffusion controls microclimate (i.e., ambient RH and Time) . At the core Temp controls moisture . Temp increase promotes moisture desorption (RH increases) . Sudden Temp change causes moisture transfer Testing in Sealed Environment Materials Exposed to Temp. Cycle inside Sealed Space - Micro-RH

Materials “control” their own micro-RH, at which point materials are taking over Field Experiment: Test Samples . Books . Paper stack in cardboard box . Photos stack in cardboard box . Matted photos in cardboard box . Microfilms Collection Environmental Zones

Zone HVAC Operation Week days A Setbacks during 6 hours Cool to 30°C OFF for up to 6 Heat to 13°C hours B No Setback. 21°C ON

C Set backs during 8 hours Cool to 30°C OFF for up to 8 Heat to 13°C hours D Set backs during 8 hours Cool to 32°C OFF for up to 8 Heat to 10°C hours

E Continuous Temp. and ON RH control Zones B and D Macro-environments Book in Zones B and D Microclimates Are Worth Looking Into . Microclimates govern decay . Help to avoid extreme situations . Help the implementation of intentional Temp. and/or RH changes without risk . Equilibration rates needs to be accounted for to assess realistic risks Enclosures and Cabinets Can Prevent Equilibration to the Worst of Summer RH Layers of Enclosure … Each layer is Outdoor permeable to some Climate Building degree, but Envelope multiple layers Storage Room impede the rate at Storage which the collection Furniture objects ‘feel’ the Enclosure worst extremes of Object summer RH Enclosures and Equilibration

• Studies show that enclosures DO NOT significantly block the transfer of HEAT or reduce the time needed to adjust to new temperature conditions • Enclosures or housing situations may act as MOISTURE barriers Enclosures and Equilibration

It has been demonstrated that real-life housing situations – books stacked tightly on shelves, objects enclosed in protective housings – may act as moisture barriers and can slow the rate of moisture equilibration even further. RH Outside (Red) and Inside (Blue) a Book RH Outside (Red) and In the Core (Blue) of Paper in a Document Box Equilibration & Buffering

RIT Wallace Library Seasonal RH Shift 2014-2016 – New Path to Sustainable RH Control • Testing of various RH control strategies to measure the impact on rate of equilibration and the energy implications • Is there a way to control environmental (macro) RH to keep materials from fully equilibrating to extreme conditions? • Single set-point changes, stepped models, etc… Concepts to take away:

• Overall, temperature equilibration of materials is relatively fast; • RH equilibration (at the core) is comparatively slow • Enclosures do very little to impact the rate of temperature equilibration • Some enclosures can have significant impact on the rate of moisture equilibration

The Next Webinar Will Explore:

Building Envelopes and Moisture Control

• Assess the Tightness of your Building • Simple Moisture Control • Air Circulation • Understand & Diagnose Microclimate Problems • Use Dew Point to Identify Ground Moisture • Consequences of Seasonal Building Closure

Next Webinar – July 8th 2:00 PM EST Sustainable Preservation Practices for Managing Storage Environments Project website . www.IPISustainability.org . Includes archived workshop and webinar presentations, reference material, videos, etc. Please take a moment to complete the post-webinar survey that will be emailed to you shortly.