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Nat, Neither is good. Causes of Deterioration Air Quality. Pollution from gases such as ozone, peroxides, sulfur oxide, and nitrogen can come from a variety of sources including photocopiers, vehicle exhaust, and paint. Even seemingly benign sources such as new carpet, cleaning supplies, paint fumes, and emissions from wooden objects can cause damage to paper. These pollutants are absorbed by the paper and form chemicals that embrittle or discolor paper. A chemical air filtration system as well as good air circulation within the building is necessary to minimize pollution damage to the collection. Light Light waves are absorbed by paper molecules causing possible photochemical reactions. Ultra Violet light is more damaging than light in the visible spectrum. Exposure of paper to light causes paper to bleach, yellow, darken, as well as accelerate paper embrittlement. Photographs are particularly susceptible to light damage which causes embrittlement, yellowing, and the fading of color in prints and hand colored surfaces. UV levels for photographs should be kept below 400 nanometers. Tungsten halogen lamps, fluorescent lamps, and mercury lamps are also damaging to paper. Materials should be exposed to light only when in use, since light damage is cumulative and irreversible. 55 lux bulbs are recommended for light sensitive materials and 165 lux bulbs for less light sensitive materials. Recommendations for exhibition lighting is 50-75 lux bulbs. UV filtering glass can be used for library windows or filtering plastic can be placed on ordinary glass windows to minimize sun light damage to materials. Pests and Mold 70 species of pests have been identified as harmful to paper. Most frequently occurring pests are silverfish, firebrats, psocids, and cockroaches. Integrative pest management is imperative to control and deter pest infestation. Mold thrives in dark, moist (over 70% RH), warm areas with stagnant air. Pests are attracted to sizes adhesives and starches and damage paper materials by eating, tunneling, nesting, and excreting. Pests seek to live in a climate of 68-86% fahrenheit and 60-80% RH, with access to food and water. Relative Humidity Relative humidity is the amount of moisture in the air at any given temperature divided by the total amount of moisture that could be held. A higher relative humidity causes oxidation, speeds up damage caused by air pollutants and light, and accelerates embrittlement of paper. High humidity also encourages mold growth and pest infestation, since the presence of moisture creates a more inhabitable environment. RH should remain constant since fluctuations cause materials to expand and contract. Fluctuations in RH can cause structural damage, distortions in paper, and weaken media attachment to paper surfaces. Ideal is humidity between 45 and 50% Mould will start to grow at around 60% relative humidity, and if the humidity fluctuates more than 10% in 24 hours or the temperature is too high, the items in the collection will become stressed, which will accelerate the deterioration process. Temperature Heat functions interdependently with humidity. High temperatures encourage mold and pest activity. Stable temperatures are recommended with a maximum of 10° F fluctuation. Ideal is temperatures between 18 and 20°C. These are tidbits from my National Archives of Australia Manuals. Why Australia? cuz they really battle these element constantly. Best, Dario @ www.vintagemovieart.ca Restoring Hollywood one Poster at A time Steven Yafet wrote: I appreciated every single comment about the effects of light (natural and otherwise) on posters. Very educational.
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- Re: [MOPO] Blackouts and thank you Dario Casadei
