What are the goals?
An artifact storage chamber will be constructed out of an empty cardboard box. Temperature and humidity will be measured over the course of a week. The measurements will be inserted into a special online “Dew Point/Preservation Metric” calculator designed to express and visualize the relationship between temperature, relative humidity and dew point to the effeteness of a storage system. Based on the results of these readings a data table will be prepared and the results potted in a series of graphs. An understanding of how the variables of temperature, relative humidity, and dew point influence each other is essential to managing storage environments.
- What is an artifact storage box?
- What is the relationship between temperature, relative humidity, and dew point?
- Did the temperature, relative humidity, and dew point remain fairly constant over the 5 day recording period?
- If the dew point were close to the air temperature inside of the storage box, what would this indicate about relative humidity?
- What is mold?
- Were there any days when the risk of a mold outbreak was high?
- When the mold risk was high what were the temperature, relative humidity, and dew point readings?
- What appears to be the relationship between temperature, relative humidity, and dew point when the mold risk inside of the storage box is high?
- What is artifact mechanical damage or deterioration?
- Were there any days when the risk of mechanical damage to the artwork and/or artifact was high?
- When the risk of mechanical damage ot the artwork and/or artifact were high what were the temperature, relative humidity, and dew point readings?
- If there were days when the mold and mechanical damage levels were high what steps could be taken to reduce or lower the levels?
In the world of artwork and museum artifacts preservation preventing material stresses and/or premature deterioration by mold are profoundly influenced by environmental conditions inside of the storage chamber. A proper environment can prevent damage, and an improper environment can cause damage. Temperature, relative humidity, and dew point are very important factors in preventing or increasing both stress induce premature artifact destruction and/or deterioration by mold.
Molds are forms of fungi found indoors and outdoors all year round. Outdoors, molds live in the soil, on plants and on dead or decaying matter. Another common term for mold is mildew. Mold growth is encouraged by warm and humid conditions, although it can grow during cold weather. There are many thousands of species of mold.They can be in any colour, including white, orange, green, brown, or black. Most fungi, including molds, produce microscopic cells called “spores” that are spread easily through the air. Live spores act like seeds, forming new mold growths (colonies) with the right conditions.
Molds do not require liquid water to grow. They only require relative humidity levels from 65% to 99% at the surface on which they grow. If the humidity is kept low enough, it is possible to prevent mold growth. Maintaining relative humidity below 50% inhibits mold and mildew growth, dust mite infestations, and bacteria all of which can have adverse affects on artworks and artifacts.
Air temperature is a measure of the heat content of the air and relative humidity is the ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air can hold at that temperature, expressed as a percentage.
A psychrometer is an instrument commonly used in laboratories to measure relative humidity. It is also referred to as a wet and dry bulb thermometer. This instrument consists of two similar thermometers that are mounted side by side. The dry bulb has its bulb exposed to the air. The wet bulb is wrapped in an absorbent material such as gauze, which is immersed in water and serves as a wick. When the web bulb is taken out of the water, it cools by evaporation of the water. The amount of evaporation, and consequent cooling of the thermometer, depends on the humidity of the atmosphere the drier the atmosphere, the faster the water evaporates.
Dew Point measures the absolute moisture content of the air. Therefore, it determines how much moisture to add or subtract (humidify or dehumidify) to achieve the appropriate relative humidity in a storage environment. The primary function of the online “Dew Point /Preservation Metric” calculator used in this science fair project is to express and visualize the relationship between temperature, relative humidity and dew point. The calculator integrates temperature and relative humidity (RH) values to estimate the rate of mold buildup and basic structural material decay that will occur in a storage system.
Mechanical stresses caused by fluctuating relative humidity and temperature can causes as much damage to artifacts and artwork as mold. A change in temperature can expand or contract metal, stone and other inorganic materials. All objects come to temperature equilibrium quickly, rarely taking more than 24 hours. In a mixed collection of artifacts, temperature change does not damage as many objects as significantly as relative humidity fluctuation. A change in relative humidity may cause warping, splitting, and dimensional changes due to moisture absorption.
A Preservation Metrics (PM) can be used to predict mold outbreaks or the risk of mechanical damage to artifacts and artwork. Determining the mold and mechanical deterioration risks for the homemade artifact storage box will be based on the results generated by a preservation metric.
- Any required diagrams/pictures (Pictures speak a thousand words!)
Digital photos can be taken during the investigation process also the following sites offer down loadable images that can be used on the display board:
- What materials are required?
Empty cardboard box, two thermometers, string, tape, small piece of fabric gauze, distilled or de-ionized water, rubber bands, Styrofoam sheet, seashell, (or animal bone, dry leaf, etc), old photograph or watercolor painting, and a computer with Internet access.
- Where can the materials be found?
Artwork and artifacts such as seashells, animal bones, dry leaves, old photographs, etc along with an empty cardboard box are readily available. All of the other items for this project can be purchased locally at most major retail (Wal-Mart, Target, Dollar general, etc) discount department stores. The Tri-fold cardboard display board and a Styrofoam sheet are available for purchase from an art & crafts supply store.
- Construct a psychrometer by attaching two thermometers firmly to a small board or sturdy Styrofoam sheet. The bulbs of the thermometers should stick out past the end of the board.
- Wrap gauze around the bulb of one of the thermometers, and tape or tie it in place. Wet the wick gauze with distilled or de-ionized water placed in a small cup. See illustration below.
- Use clean hands to do the assembly. Any dirt or grease on the wick gauze or thermometer will interfere with accuracy.
- Avoid using tap water to saturate the wick gauze or to wet the bulb. It could contain certain salts or other substances that will hinder uniform evaporation.
- Tape the psychrometer assembly to the inside of a dry empty cardboard box. Place the small cup inside the box containing distilled water and suspend the end of wick gauze into the water, so that it and the thermometer bulb are both wet.
- Place a piece of artwork and/or artifact (seashell, animal bone, dry leaf, etc) in the box.
- The entire setup should appear as shown below.
- Take an initial reading before sealing the box. The dry bulb thermometer reading should remain constant. The wet bulb thermometer reading should stop changing within two or three minutes after it is saturated with water. When the wet bulb reading is stable, write down both the dry bulb and wet bulb readings.
- To figure out the relative humidity inside the storage box, subtract the dry bulb reading from the wet bulb reading, then use a table similar to one shown below. NOTE: Do Not consult this table if using thermometers with the Celsius scale instead search for a table on the Internet design to be used for metric humidity measurements.
- Be sure to keep one thermometer completely dry and make sure that other thermometer remains wet at all times.
- Using a computer with Internet access link to the “Dew Point/Preservation Metric” calculator website at http://www.dpcalc.org/
- The calculator will appear as shown once it is accessed and displayed on the computer screen.
Graphics courtesy of the Image Permanence Institute at Rochester Institute of Technology
- Move the onscreen sliders for temperature and relative humidity that corresponds to the readings taken inside the storage box.
- Record the storage environment in the box based on the data generated by the calculator in a table similar to the one shown.
|Day/Time || Air Temperature||Relative Humidity (%HR) ||Dew point ||Mechanical Damage (%EMC) ||Mold Growth Risk|
|1/|| || || || || |
|2/|| || || || || |
|3/|| || || || || |
|4/|| || || || || |
|5/|| || || || || |
- Take temperature and relative humidity readings at regular intervals over the next five days. Enter the results into the calculator and record the data generated in the table. The data from the online calculator can be downloaded and printed by clicking on the onscreen “Export” button.
- Using sheets of graph paper or a computer equipped with Excel® visually display the data in the table by plotting a series of line graphs for temperature, relative humidity, dew point, and per cent of mechanical damage similar to the graphs shown.
- A possible project extension is to compare the environmental storage conditions inside of a commercially manufactured artifact storage box to that of a homemade storage box, following the same procedure outlined for this project.
Terms/Concepts: Temperature; relative humidity; dew point; Preservation Metrics; mold; mechanical damage; artifact storage box
References to related books
Title: The Kids' Book of Weather Forecasting
Author: Mark Breen and Kathleen Friestad
Publisher: Williamson Books ISBN-13: 9780824968236 andISBN: 0824968239
This fact-filled book is arranged into eight chapters, and guides the reader through the observation process. Instructions for keeping weather log and the importance of detailed, accurate records is explained. Directions for making and using simple weather instruments are found throughout the text including instructions on how to make a psychrometer.
Title: Weather Words and What They Mean
Publisher:Holiday House, Inc. ISBN-13: 9780823409525 and ISBN: 082340952X
Links to related sites on the web
Title: What Exactly Is The Dew Point?
Title: Make Your Own Psychrometer
Title: Mold & Moisture: What Are the Facts?
Title: What Temperature and Humidity Combinations Generate Mold?
Title: Initial Processing of Archaeological Materials
Title: How temperature and Relative Humidity affect Collection Deterioration Rates
NOTE: The Internet is dynamic; websites cited are subject to change without warning or notice!