Monday, 28 January 2013

OUGD404 - Design Principles: Group Colour Study Task

Why do natural colours fade?

UV Filters Do Not Stop Fading, They Help Reduce Fading...

Visible Light is produced within the spectrum of electromagnetic energy that includes radio waves, microwaves, X-ray and ultraviolet (UV) rays.The cause of fading is due to a photochemical reaction involving UV and visible light.

Research has shown (above) that 40% of fading is caused by UV rays.Another 25% of fading is due to heat, with 25% being caused by normal visible light.The remaining 10% cause of fading is from indoor artificial lighting, humidity, and poor dye anchorage.Visible light and UV radiation cause fading and a lack of moisture, especially in the cloth materials used to cover books.

Electromagnetic energy is measured in nanometers (nm.)UV is present from 100-400nm, and visible light is present from 400-700nm.The energy that exists from 100-700nm is thererfore responsible for 65% of all fading. These wavelengths are very damaging to library materials, dyes, papers, wood, paintings, photographs, and even the foods we eat.
  • UV-A rays cause more serious long-term damage. They penetrate and ruin your carpets, fabrics, window treatments, wall coverings, and fine wood furnishings.
  • UV-B rays quickly bleach and burn surface colors.

Due to newer pollution control laws, the dyes used in fabrics, paints, wood stains and coatings available in home improvement centers have been formulated to have a minimal impact on our environment. Unfortunately, some are of these materials are less stable than the dyes, paints, stains and coatings that have been used in the past. That is because the older materials were usually solvent-based. While the water-based products we use today are more environmentally-friendly, they are more vulnerable to fading in time.

UV rays (found either in sunlight or artificial light such as fluorescents) act as a bleaching agent. Through a complex process, UV rays transform the water found in all fabrics into hydrogen peroxide, (a common bleaching agent) that leads to the fading of dyestuffs. High energy photons of light, typically found in the ultraviolet or violet spectrum, can disrupt the bonds in the chromophore (a chromophore is the part of a molecule that is responsible for its color), leaving the resulting material colorless. Extended exposure to UV and visible light often leads to widespread discoloration.

People in the clothing, drapery, carpeting, upholstery and other textile related industries know that after fabrics are exposed to fluorescent lighting for a period of time, the color dyes used in fabrics fade. Have you ever browsed through clothing sections in a department store?The next time you do, look at the jackets, blouses, coats, and sweaters hanging on the racks.If they have been there for any length of time, you can spot the fading. Look along the hanger-line, and notice the amount of fading that occurs there.The same is true of clothing that has been overlapped on store shelves.To see the amount of fading, simply lift up the top article of clothing and look for the effects of fading on the one below it.

NaturaLux™ Filters absorb 100% of the harmful UV rays up to 380nm. That means all UVB and almost all of the UVA is absorbed as well. 81-99% of the UVA found between 380-390nm is absorbed. From 390-400nm, there is an 50-80% UVA absorption rate. This means that your overall exposure to UV from fluorescent lighting is practically non-existent.

NaturaLux™ Filters are designed to reduce the fading process by absorbing the UV and visible light rays that ultimately damages your valuable possessions.

Image: Blue fruit
Vignolini et al., Cambridge / PNASThere's an iridescent blue sheen to this cluster of fruits from an alcohol-preserved specimen of Pollia condensata collected in Ethiopia.
updated 9/10/2012 4:36:56 PM ET2012-09-10T20:36:56
Scientists have found nature's way of creating color that never fades, a technique they say could replace pigments used in industry with natural plant extracts in products from food coloring to security features in banknotes.
Layers of cellulose that reflect specific wavelengths of light — "structural color" found in peacock feathers, scarab beetles and butterflies — make a particularly intense blue in the Pollia condensata plant, scientists say.

Samples of the fruit in plant collections dating back to the 19th century had not lost any shine or intensity, they found.

"By taking inspiration from nature, it is possible to obtain smart multifunctional materials using sustainable routes with abundant and cheap materials like cellulose," said University of Cambridge physicist Silvia Vignolini.

"It is 10 times more intense and bright than any color achieved with a pigment," said Vignolini, who led the study with plant scientist Beverley Glover.

Although the fruit has no nutritional value, birds were attracted by its bright color, possibly as a decoration for their nests or to impress mates, helping in seed dispersal.

"This obscure little plant has hit on a fantastic way of making an irresistible, shiny, sparkly, multi-colored, iridescent signal to every bird in the vicinity, without wasting any of its precious photosynthetic reserves on bird food," said Glover.
And, unlike pigments, structural color does not fade over time as it is not broken down by absorbing light.

"Edible, cellulose-based nanostructures with structural color can be used as substitutes for toxic dyes and colorants in food," said Vignolini. The paper industry is already set up to extract and use cellulose and its processes could also be adapted for security labeling or cosmetics, she said.

"Cellulose-based structures have a really strong optical response and are completely inert in the human body," she said.

Another advantage of the technique is that the desired color can be achieved by adding layers in the structure to reflect different wavelengths, rather than buying new pigment.

Similar research by Peter Vukusic at Exeter University into the structure that creates color in butterfly wings has spawned a pigment-free photonic make-up from French cosmetics company L'Oreal.

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