1/22/2019 DEMYSTIFYING SILICA GEL FOR EFFECTIVE MICROCLIMATES JANUARY 22, 2019 RACHAEL PERKINS ARENSTEIN A.M. ART CONSERVATION Did you know that the internal surface area of a teaspoon of silica gel beads is equivalent to that of a football field? This amazing property makes silica gel a relatively low-cost method for protecting collections on display and in storage from inappropriate or fluctuating environments. But not all silica gel is created equal. • Are you curious as to why silica from preservation vendors is more expensive than other desiccants or gel from commercial vendors? • Have you found loose silica beads or cartridges and pondered why it no longer seems to be “working”? • Interested in guidance on how much to use for your application? Whether it comes in sachets, cartridges or loose beads, the manner in which it is installed and cared for will greatly affect its efficacy. This webinar will focus on understanding the different types of gel, why it matters which you use, and how to calculate appropriate amounts for use in a vitrine or storage cabinet. The basics of appropriate preservation environments, creating a safe microclimate and how to monitor the environment within will be touched on. N.B. This version of the presentation contains additional information that was not included in the live webinar on January 22, 2019. C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 1 1/22/2019 Access the presentation at: https://www.connectingtocollections.org/effective-microclimates/ C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 1 1/22/2019 OUTLINE • OVERVIEW OF AGENTS OF DETERIORATION, TYPES OF DAMAGE & THE NEED FOR ENVIRONMENTAL CONTROL • WHAT IS A MICROCLIMATE? • HOW DO WE CONTROL MICROCLIMATES? • WHAT IS SILICA GEL? • USING SILICA GEL EFFECTIVELY • CALCULATING AMOUNTS • PLACEMENT • MONITORING • RECONDITIONING • STORING I’m pleased to be able to talk to you today about silica gel and how we can use it to meet some of the environmental needs of our collections. While serving as a member of the Connecting to Collections Care Professional Development Working Group I volunteered to present this topic as I was spending a lot of time working with my museum clients correcting misunderstandings about silica gel and how it can be effectively used. For those of you who already have a sense of collection care basics, I hope that you’ll stick with me while I first review some introductory material on deterioration and environmental control. This foundation is important in understanding our environmental needs and whether they can be fulfilled by using silica gel in a microclimate. Then we’ll get into the nitty gritty of silica gel types and formats and how to use it properly in common museum applications. I hope that after this presentation, even if you feel that using some of the equations isn’t your thing, that you will be able to ask good questions of a preservation vendor in choosing a gel for your particular application. POLL #1: Are you using silica gel… • In storage cabinets or microclimates • In exhibition vitrines C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 2 1/22/2019 • Both • I’m not using silica gel but want to know more C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 2 1/22/2019 REVIEW OF ENVIRONMENTAL ISSUES C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 3 1/22/2019 Types of Deterioration Chemical Mechanical Biological http://protectheritage.com/Lisbon2011/wp-content/uploads/2011/12/Linden-frinal-corrected-reduced-file-size.pdf Our goal, as collection care and preservation professionals is to extend the life of the material in our care. I find the way that the Image Permanence Institute discusses deterioration to be useful in understanding what we are concerned about. IPI uses three broad categories: • Chemical • Mechanical • And Biological Chemical deterioration refers to the reactions occurring within the object. This occurs naturally and inevitably as an item ages but can be sped by environmental factors such as temperature. Examples include change of color in photographs, fading of dyes, degrading plastics or foams, weakened textile fibers, yellowed and embrittled books and paper and corrosion of metal artifacts. Mechanical refers to physical damage such as cracking, warping, delamination, slumping. Cracking like that seen on this wood sculpture is an example of mechanical damage caused by fluctuating relative humidity. Biological damage means i.e. mold/fungi or insects and vertebrate pests. These biological factors that act on art can be heavily influenced by the environment. Mold growth requires periods of sustained high humidity and humidity. Elevated C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 4 1/22/2019 temperatures will speed insect reproduction cycles and some insect pests are known indicators of high humidity as they feed on mold and fungi. Images: Jeremy Linden “Preservation Metrics: A Preservation Analysis Tool for Risk Analysis in Preventive Conservation” http://protectheritage.com/Lisbon2011/wp- content/uploads/2011/12/Linden-frinal-corrected-reduced-file-size.pdf C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 4 1/22/2019 Agents of Deterioration Environmental Agents • Incorrect relative humidity (RH) • Incorrect temperature • Light • Pollutants https://www.canada.ca/en/conservation-institute/services/agents-deterioration.html We often speak about the Agents of Deterioration, which are defined as primary threats to our collections. Probably the best description of these 10 general categories, is available on the Canadian Conservation Institute’s website. Our job is to determine how we can detect, block, report, and treat the damage these Agents cause. Today we are going to focus on one of the Environmental Agents - Incorrect Relative Humidity or RH, as it is a major factor into all three forms of deterioration. Reference: CCI website https://www.canada.ca/en/conservation-institute/services/agents- deterioration/humidity.html#tft2a C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 5 1/22/2019 Incorrect Relative Humidity 1. RH too high 2. RH too low 3. Fluctuating RH 4. RH above or below an object specific critical value https://www.canada.ca/en/conservation-institute/services/agents-deterioration/humidity.html#tft2a CCI breaks down Incorrect RH in four ways. https://www.canada.ca/en/conservation- institute/services/agents-deterioration/humidity.html#tft2a 1. RH too high – High relative humidity is responsible for corrosion of metals, mold growth and mechanical damage of hygroscopic organic artifacts. High RH is generally considered 65% and above. Mold germinates at 70% and above so most guidelines for upper RH limits top out around 60%. 2. RH too low – Organic materials will lose moisture to the ambient environment if RH is too low. Generally, 30% is considered the lower limit. Below that, artifacts may shrink becoming desiccated and embrittled.. 3. Fluctuations in RH – This has been, for many institutions, the most problematic issue in environmental control. When RH fluctuates, the moisture content of the artifact will fluctuate as the piece seeks equilibrium with its environment. This results in expansion and contraction. For artifacts made of multiple materials that react differently to changes in RH, or artifacts that are constrained or under tension, the differing rates of equilibrium can cause cracking, splits and other forms of C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 6 1/22/2019 damage. 4. RH above or below an object specific critical value – There are some types of artifacts that have specific environmental needs based on their materials, composition or condition. For instance archaeological metals benefit from low RH while unstable glass requires a moderate 40-60% RH. So our goal is to prevent extremes, and other times it is to provide a specific set of conditions. Images: eClimateNotebook Graphs: Author’s and IPI’s https://www.imagepermanenceinstitute.org/resources/newsletter- archive/v20/ipi-research-equilibration C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 6 1/22/2019 http://www.conservation-us.org/docs/default-source/hhi/hhisummary.pdf?sfvrsn=2 And we know that we often have trouble doing it. The Heritage Health Index Report published in 2005 was the first comprehensive survey to assess the condition and preservation needs of U.S. collections. And the report documented the challenges that many institutions have in creating appropriate environments for long-term preservation of our nation’s cultural heritage. A quarter of institutions reported no environmental control for their collections. And clearly, even ones that did had seen damage. So you are not alone if you are grappling with these issues. Heritage Health Index Summary report - http://www.conservation-us.org/docs/default- source/hhi/hhisummary.pdf?sfvrsn=2 C2C Care Webinar, Demystifying Silica Gel for Effective Microclimates, Arenstein 7 1/22/2019 The 70/50 Debate https://www.academia.edu/1500445/2010._The_Plus_Minus_Dilemma_A_Way_Forward_in_Environmental_Guidelines The Heritage Health Index Report resulted in a number of initiatives, among them the C2CCare platform we are on now, aimed at providing information to address preservation issues. And, along with that we also have seen