In a previous post I introduced you to Blue Wool cards and discussed how you can use them to quantify light exposure without having to invest lots of money in expensive light meters. In this post I will show you how you can use Blue Wool cards to protect your paper based collections and collectibles from to being exposed to too much light. As before, the information in this blog post applies to baseball cards, comics, posters, paper art prints, as well as philatelic stamp art. As a reminder, Blue Wool cards include rows/stripes of pigmented fabric that are calibrated to indicate cumulative exposure to different amounts of light. Over time, starting with the top stripe, and working down, each stripe begins to fade based on increasing amounts of light exposure. An indication that a stripe has begun to fade can be used as an indication of a particular amount of light that the stripe has been exposed to. In this way, a Blue Wool card placed next to your paper based collectible can be used as an indication of how much light your collectible has been exposed to. This knowledge alone is valuable, but when combined with one other piece of information, Blue Wool cards can be very cheap and powerful tools in the hands of those interested in paper conservation and preservation. As I have mentioned, each stripe has particular pigments/dyes that are known to fade in a similar manner to that of known historic items. For example, the 5th stripe from the top is know to mimic the light fastness of of the colors used in many modern 20th century stamps. Thus, the amount of time it would take the 5th stripe fade, is the same amount of time it would take for a 20th century stamp to fade when exposed to the same amount of light. The amount of time it takes to cause a stripe to show evidence of fading can be analogized to that of filling of a "light bucket," with each exposure to light acting to fill the bucket with an added quantity of lux (a measure of the amount of visible light per unit area at the surface of an object where the closer a light source is to an object, the higher the lux will be). It is known that the light bucket of the 5th stripe from the top will overflow after about 32 Megalux hours of cumulative VISIBLE light exposure. Lower intensities of light will of course take longer to fill the light bucket. Confused, sets use the chart below to help explain the light bucket concept further. What the chart shows is how much LUX different amounts of typical light emit. VISIBLE Light Condition Light at Surface of an Object (Approximate) Direct Bright Sunlight 100,000 lux Shade in Direct Bright Sunlight 10000 lux Direct Bright Sunlight in a room 5000 lux Halogen Lamp 700 lux Typical Fluorescent Room/Office Lighting 300-500 lux Typical 100 watt bulb at a distance of 3 ft 100 lux Museum Lighting 50 lux for sensitive materials (i.e. stamps) Wax Candle at 1 ft 10 lux Full Moon 1 lux Effects of Indirect Sunlight Thus, exposure of the 5th stripe of the Blue Wool cart to the 10,000 lux of indirect full sunlight, 8 hours a day, over 1 year (365 days) would cause the 32 Megalux bucket represented by this stripe to be filled with 10,000-lux x 8 x 365 of lux, or equivalently about 29 Megalux, an amount of illumination that would be just short of causing visible fading of a modern stamp. Effects of Office or Room Light The analogy above can be extended to understand the effects of any lighting condition. Lets consider the cumulative exposures to light that would occur in a typical room/office illuminated by bright fluorescent lamps (500 lux), in which case, with 8 hours of illumination each day for one year, a modern stamp would be exposed to (500 x 8 x 365) or 1.5 Megalux over one year. At this rate, the 30 Megalux bucket of the modern stamp would begin to overflow/fade after about 20 years of cumulative illumination (30 Megalux = 1.5 Megalux x 20 years) under normal office or room light. Using a similar calculations, when exposed under 50 lux of illumination (proper museum lighting), even moderately lightfast materials like modern stamps would evidence fading in about 200 years. If 200 years seems to you to be very far in the future, consider the Declaration of Independence, which is displayed in the National Archives under light conditions that are much less that 50 lux, and but for this low level of light would long ago have faded from existence. Hopefully you will by now understand how it is that you can use Blue Wool cards to protect your paper based collections and collectibles from to much light exposure. By placing a Blue Wool card next to your collectible, you can monitor how much light it has been exposed to. Assuming you know what the light fastedness of your particular treasured item is, you can anticipate whether or not it has reached a point when if will begin fading and protect it, before it does so, by removing it from the light. BUT, before you quickly conclude that 50 lux, 200 lux, or some other amount of VISIBLE light illumination is an acceptable amount of light you can expose your collections to because the calculations above show that it would take hundreds of years before they would show signs of fading, I advise you to wait for my next post on "What Is a Safe Amount of Light Exposure - Part 3". For those of you that can't wait - the answer is very simple, there is NO safe amount of light exposure for paper based collections.
In one of my previous posts about light and its harmful effects, I asserted that exposure of your baseball cards, comics, stamps and other paper based collectibles to seemingly small amounts of ordinary room light can cause fading of your collection. In this post I will show how it easy to quantify such fading without having to use expensive electronic instrumentation. Our discussion begins with the "Blue Wool" cards below, which many museum curators use to estimate the effects that museum lighting has on various pigments, dyes, paints, papers, and other non lightfast materials. The Blue Wool cards comprise a set of horizontally dyed stripes. What is of particular interest about the blue wool cards is that the light fastness of the pigments of the dyes in the stripes can be used to mimic that of many items of history, and value, for example, stamps and art. By placing the cards/stripes at desired locations, the cumulative fading effect of any light in the vicinity of the cards can be visually quantified. It takes about 3 times the amount of cumulative illumination to fade each stripe as the stripe that is directly above it. For example, depending on geographic location, season, humidity, the 3rd stripe from the top will begin to fade after exposure to about 3.6 Megalux hours of illumination, the 4th stripe from the top will begin to fade after exposure to about 8-10 Megalux hours, and the 5th stripe after about 30 Megalux hours. The middle blue wool card above shows a lengthwise left section protected from all light by aluminum foil (Al), a middle section that is not protected at all, and a lengthwise right section that is protected with an ultraviolet (UV) filter. The right blue wool card shows the aluminum foil and ultra-violet (UV) filter removed after the dyed stripes on the card were exposed for 8 months to the light of a south facing Canadian window. Comparison of the middle section of the middle and right card above against the corresponding right section illustrates one point that your beach going experience should have taught you; that exposure to ultraviolet UV light should minimized, which in the case of paper based collectibles can be accomplished via use of UV filters. A more important philatelic observation is this: even when when protected by ultra-violet UV filters, your stamps and paper based collectibles can be damaged by the visible light component of light. This is the reason the right sections of the middle and right blue wool cards above show fading. Why? ... because of something many collectors fail to consider ... that UV filters DO NOT filter VISIBLE wavelengths of light. However, the most important take away is this: although blue wool cards above show that filtering of ultra-violet light does indeed reduce fading and damage, they illustrate that every time VISIBLE wavelengths of light are used to view your philatelic collections (whether or not ultra-violet UV filters are used) fading and/or damage will occur. In fact, each exposure to VISIBLE light will irreversibly and cumulatively add to any previous stamp fading or damage that has already occurred; the additive effects of exposures to such light is known as "reciprocity." This is one of the reasons that the British Guiana looks like it does. But, although I have illustrated that blue wool cards can be used to measure and quantify light exposure, I have not yet shown how it is that you as a collector can make use of them to protect your collections. I'll do so in my next post.
You would think that all museums would be worried about damage to their collections from light. Well you thought wrong. What are these pictures doing here - read my post about the damage that direct and indirect sunlight and indoor illumination can cause to your collections, whether they be art, stamp, comic or baseball card based. Compare the images below the image of the William Gross Exhibit at the National Postal Museum. The National Postal Museum knows there "stuff". Their rarities and treasures are exposed to light only when a person's body is sensed and kept darkened otherwise, which over the lifetime of the stamps being exhibited, will greatly reduce any fading or other damage they might suffer otherwise - your Federal government isn't as incompetent as you may have thought, is it? :lol: Images from "HOW TO KEEP FOR A WHILE WHAT YOU WANT TO KEEP FOR EVER" by Tim Padfield http://www.padfield.org/tim/cfys/phdk/phdk_tp.pdf