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Wednesday, July 24, 2013

The Truth About Optical Brightening Agents

Optical brighteners are organic compounds that by themselves are colorless, but when added to a substrate (such as canvas and paper) they make colors appear brighter and give them a pop. The way they do this is that they change the visible wavelength of the light being reflected off the surface and this makes it appear brighter.
        Visible colors are determined by the wavelength of light that is reemitted from the canvas after it is absorbed and OBA’s alter the natural refractive properties of a canvas.Adding OBA’s can enhance the colors visible on a surface by making more of ultraviolet (UV) light is reflected in a visible color spectrum. When invisible ultraviolet light hits a substrate it has a wavelength of 300-400 nm and when it leaves a canvas enhanced with OBA’s it leaves in the visible spectrum of 400-500 nm.
This means to a printer that the inks they use will have more of a pop and vibrance then the canvas or paper would naturally have. Altering canvases in this way means that you can use a canvas that does not have great reflective properties and enhance them, instead of using a high quality canvas that does. This makes cheaper canvas’s that can rival or even exceed the color qualities of more expensive, well-designed substrates.
While this sounds like a great advancement in the field of printing, OBA’s tend to fade from a substrate over the years and lead to yellowing. After the fading there is a much poorer quality paper or canvas that has lost the chemicals that made it appear so good. Instead of having your original high quality print, with great colors, instead you have a poor quality print with incorrect color composition and a yellowed surface.
This is why one should look for rolls made with little or no OBA’s, although they generally carry a much higher price tag, they keep their appearance through the years. In addition, advancements in the industry have led to canvas and papers that look almost as good as OBA enhanced papers. Your prized photos will keep their great colors and remain as they are for years to come.  
Our Eco-Solvent/Solvent is OBA free and can be viewed here, Eco-Solvent Canvas . The vast majority of products that are sold contain some OBA brightening agents, however, as that is what the industry usually uses.