INFS 423 Preservation of Information Resources

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1 INFS 423 Preservation of Information Resources Lecture 4 Deterioration by Light Lecturer(s): Prof. Harry Akussah & Mr. Michael Allotey Contact Information: mallotey@ug.edu.gh, hakussah@ug.edu.gh School of Information and Communication Studies Department of Information Studies 2018/2019

2 Lecture Overview Last week, I led you through some of the factors that could influence negatively the longevity of documents and how to control and monitor temperature and humidity. In this lecture, I will introduce you to light as a factor of deterioration, the damages it can cause to your documents and how to monitor and control it. Slide 2

3 Lecture Outline The key topics to be covered in the lecture are as follows: 1. Defining Light 2. Sources of Light 3. Composition of Light 4. Types of Artificial Lights 5. Damages Caused by Light 6. Monitoring Light 7. Topic Seven: Control of Light Slide 3

4 Reading List Akussah, H. (2011). Preservation of Documents. Department of Information Studies, Legon, NAB Superior Services. Gorman, G. E., & Shep, S. J. (2006). Preservation management for libraries, archives and museums. London: Facet Pub. Adcock, E.P. (2000). Principles for the care of handling of Library Materials. Washington, D.C., IFAPAC. Swartburg, S. G. (1983). Conservation Library. A Handbook of use and care of traditional materials. Connecticut: Greenwood Press, Feather, J. (2004). Managing preservation for libraries and archives: current practice and future developments. Aldershot, Hants, England, Ashgate Publishing. Slide 4

5 Topic One DEFINING LIGHT Slide 5

6 What is Light (Radiant Energy) Light can be defined as radiant energy from either the sun or from artificial sources. Lighting should be adequate for comfortable reading and work. However prolonged exposure can cause damage to documents. Damage from light is irreversible, and cumulative. Therefore the quantity and quality of light that falls on documents must be controlled. Slide 6

7 Topic Two SOURCES OF LIGHT Slide 7

8 Sources of Light Natural Light Artificial Light Example: Sunlight Moonlight Example: Light Emitting Diodes (LEDs) Fluorescent Lamps Incandescent Lamps etc. Slide 8

9 Topic Three COMPOSITION OF LIGHT Slide 9

10 Composition of Light Ultraviolent Radiation Sunlight = 40% Fluorescent = 2-12% Infra-red Radiation Heat component (Incandescent) Visible rays Slide 10

11 Ultraviolet (UV) Rays Primary source of UV rays is Sunlight and fluorescent lights. UV rays are not visible to the human eye but most damaging to documents. Responsible for photochemical deterioration - Fading, color changes, brittleness, cracking and delaminating and break up of the bond to bond holding of documents are all results of degradation caused by UV rays. Slide 11

12 Infrared Rays Infrared rays are not visible but are felt as radiant heat. Infrared radiation causes temperature to rise and materials to become heated; this accelerates the rate of chemical activity and lowers relative humidity. The major sources of infrared rays are sunlight and incandescent bulbs. Slide 12

13 Visible Rays This the part of light spectrum that we actually see as light. Although not as damaging as UV rays, high levels of visible light is still damaging to documents. Slide 13

14 Topic Four TYPES OF ARTIFICIAL LIGHTS Slide 14

15 Types of Artificial Lights Light Emitting Diodes (LEDs) Tungsten-Halogen (Quartz-Halogen Lamps. Fluorescent Lamps Incandescent (Bulb)Lamps High Intensity Discharge (HID) Lamps. Candle Slide 15

16 Light Emitting Diodes (LEDs) LED is a chemical chip embedded in a plastic capsule. several LEDs are sometimes combined to produce a single light bulb. They give off very small amount of UV rays They are the most energy efficient on the market today Slide 16

17 Fluorescent Lamps The most common source of UV rays after natural light. Slide 17

18 Incandescent (Tungsten) Lamp The normal light bulbs found in homes. They give off very little UV rays and their warm colored light is much safer for paper-based documents. Slide 18

19 Tungsten-Halogen Lamps These are small and efficient light sources. Depending on the model, they give off significant levels of UV radiation and heat. These lights should not be installed inside enclosed spaces and should always be shielded. Slide 19

High Intensity Discharge (HID) Lamps They are similar to fluorescent lamps and require some time to light up completely after they are turned on.

20 High Intensity Discharge (HID) Lamps They are similar to fluorescent lamps and require some time to light up completely after they are turned on. Types: High pressure sodium lamps: Give off very little UV rays Mercury and metal halide HID lamps: Give off very high UV rays and not suitable for indoor lighting. Slide 20

21 Topic Five DAMAGE CAUSED BY LIGHT Slide 21

22 Damage Cased by Light Visible Damage Invisible Damage Slide 22

23 Visible Damage Bleaching: Light has a bleaching action, causing colored papers and inks to turn white or fade. Upon exposure to light, lignin in paper reacts with other components to form acidic compounds which turn the paper brownish. For example, newspapers left outdoors for a day or two provide graphic evidence of this effect. Slide 23

24 Invisible Damage Ultra-violet rays spark off chemical reactions which result in the weakening and the ultimate breakdown of paper documents. Light speeds up oxidation causing materials to deteriorate faster. Light damage is cumulative: brief exposure under relatively high intensity can be just as damaging as extended exposure to low intensity. Chemical reactions initiated by exposure to light continue even after the light source is removed and materials are put into dark storage. Slide 24

25 Activity 1 Take time off your books, go and buy Daily graphic for the day and photocopy of a page of your course book. Expose the two (Graphic and photocopy) to the sun in the compound of your house or workplace for five hours. After the period, observe and describe the changes that have taken place on each of the documents. Slide 25

26 Topic Six MONITORING LIGHT Slide 26

27 Monitoring Light It is possible to measure the level of light in an area. The process of measuring light, while not overly complicated, does require some specialized equipment. It is measured using photometers and UV monitors. Slide 27

28 Measurement of Light Light is measured in the following units: Foot candles Lumen Lux Watts (does not measure light output but the energy efficiency of light) Slide 28

29 Measuring Units of Light Measuring Unit Foot-Candle Lumen Lux Watt Description Measures the amount of light reaching a subject. (Measures the Intensity of light) The amount of light that a light source produces Lux is used to measure the amount of light output in a given area - one lux is equal to one lumen per square meter. (Measures the intensity of light) Measures the amount of electricity consumed by a light source (does not measure Slide 29 light output.)

30 Recommended Light Levels For Reading 30 to 60 foot candles OR 300 to 600 Lux Storage Area 20 to 40 foot candles 200 to 400 Lux For ultra-violet radiation, any level above 75 microwatts per lumen is dangerous and therefore needs to be filtered. Slide 30

31 Instruments for Measuring Light Light Meters Photometers Ultraviolet (UV) Monitors Slide 31

32 Activity 2 Visit a public library or archives close to you. Find out the following: the type of artificial light in use the voltage of the lights whether they have ultra-violet filters. Discuss the implication of your results. Slide 32

33 Topic Seven CONTROL OF LIGHT Slide 33

34 Control of Light Ideally 100% of total darkness should be maintained at storage centers. But this is impossible, thus the following: it is possible to reduce the effects of light by keeping all materials covered or boxed when not in use and by providing only the minimum amount of light necessary for any required task involving documentary materials. Sources of natural light should be cut off. Windows should be sited so as to admit as little light as possible Slide 34

35 Control of Light Storage areas should not have windows Storage area should be lighted with low voltage sources of light All lights should be turned off when storage area is not in use As far as possible, box or wrap valuable documents. Cotton curtains can be used on windows. Slide 35

36 Control of Light Ultra violet filtering materials should be used over fluorescent. Titanium Dioxide should be used. Documents Should not be exposed to flood lights. Avoid permanent exhibitions All light in exhibition cases should be filtered. Slide 36

37 Summary You have successfully completed this Session 4. You have learnt the following: Types of light Composition of light Damages caused by light Monitoring light levels and Control of light intensity and illumination Slide 37

Westinghouse. Lamps 101

Westinghouse. Lamps 101 Westinghouse Lamps 101 Objectives Explain common lighting terminology to your customers Examine color temperature and explain the Kelvin scale List features and benefits of various lamp types, including: