What does UV light do to your print?
Ultraviolet light is electromagnetic radiation and has a wavelength of 10 nm to 400 nm. Whilst generally invisible it is present in sunlight and is produced from electric arcs, tanning lamps and black lights as examples. UV light as we know causes sunburn when we expose ourselves and this is basically what is happening when printed images are exposed to light. The UV light fades different parts of the image overtime.
There is 2 basic UV concepts that relate to the printing and framing industry and they are UV stabilisation and UV protection but before I discuss this understanding the UV spectrun is important.
- UV light is split into 3 main wavelengths.
- UVC 100-290nm - these wavelengths are mainly stopped by the ozone layer and do not cause a problem.
- UVB 290-320nm - these are the wavelengths that cause sunburn and the reddening of the skin.
- UVA 320-400nm - these are the wavelengths penetrate more deeply and cause greater problems and in the case of skin most cancers and ageing.
- UV Stabilisation. In basic terms this is when an additive is added to liquids to neutralise the effects of the free radicals produced by the UV light. There are generally 2 accepted processes by which this is done:
- UV Stabilised Inks: Inks have a "secret" additive from the manufacturer to assist in the neutralisation of the free radicals which break down the molecular structure of the ink. This applies to dye inks and the dye sublimation style inks used in processes like HD Aluminium which unlike prints and canvas there is another layer of protection over the HD Aluminium has no further protection and is totally reliant on the stabilisers in the ink. To date no independent lab testing has been done on these style of prints and all claims of longevity are from the suppliers and manufacturers only.
- UV Stabilised Lacquer: The lacquer used to coat and protect canvas, contains stabilisers which again neutralise to the free radicals from the UV light. The problem with this style of UV protection is it has a limited life because once all the stabilising molecules are all used by the reaction with the free radicals produced by the UV light, there is no protection left from a UV point of view for the image. This doesn't allow for the fact that UVA wavelengths will penetrate the lacquer and be working on the ink molecules which is why the best form of UV protection is a filter as discussed below. The image will fade at different rates as different areas of protection are used but until you place it next to a new one it is hard to notice the damage until it is too late.
- UV Filter or Glazing: This concept involves placing a filter known as glazing on or over the print to stop the UV light. There are two main types of filters used on framing photography:
- Glass: There are a number of glass options when it comes to framing, with the most common being float glass or soda lime glass. Generally a lower cost option and is the industry standard for framing. Float glass will block about 40% of UV light which basically equates to blocking all of the UVB wavelength but not much pf the UVA wavelength. There are a number of better quality glass options and they come with an associated price but they can go up to the Tru Vue Museum Glass® which blocks 99% of ultraviolet light. Float glass is the Paul Arnold standard unless higher quality is requested.
- Acrylic. Again there are a number of options here and they all offer varying rates of UV protection from around 70% to 99%. The advantage of acrylic it stops not only the UVB rays but also the more damaging UVA rays. The Paul Arnold standard is the museum grade of 99%.
So in short what does all this mean for you the consumer. Here is a summary in terms of quality for finishes: (Remember all components used are are of the highest standard and the comparison is relative to the other products listed)
Prints: Printed as per the specifications here . UV stabilised inks are used and the highest quality papers but prints need glazing to protect them form UV light and other contaminants.
Canvas: Canvas has the image printed directly onto the canvas and coated with a UV lacquer. This is the industry standard and basically when it comes to archival quality and longevity would be one of the lower rated products as it only stops UV light by way of stabilisation not glazing.
HD Aluminium: This is a dye sublimation process by which heat and pressure are used to infuse UV stabilised inks into a layer that is placed on the aluminum during manufacturing. Therefore the only UV protection is the stabilisation in the inks. The process does not meet industry standards for archiving artwork and has not been tested by professional laboratories. On a side note we have tested claims of this product and we liken it to womens nail polish - It will chip easily as it is simply layers on top of the metal. We do not recommend this product as it is inferior to other methods of displaying an image.
Framed Images: A framed print using UV stabilised inks printed to the correct standards to promote longevity. The print is then protected by float glass which blocks some of the UV light. Therefore the high quality UV stabilised ink is further protected by blocking the incoming UV light. This protection can be increased by using higher grades of glass or acrylic which are available on request.
Acrylic Mounts: In terms of archival longevity these are one of the highest quality options available. Not only is the print printed as per previously mentioned standards, but it is then mounted between museum grade acrylic blocking 99% of UV light and an opaque acrylic back for protection. In other words you can view an image in utmost clarity knowing all the harmful UV light is blocked from damaging your print.