People believe that UV Filtering means 100% protection from Ultraviolet radiation (UVR), period. Most do not know or understand that UVR is a segment on the Electromagnetic spectrum i.e, a range of electromagnetic waves. Maximum Filtration should occur across the entire UV spectrum, not a single point.
UV Filtration at its core is the amount of UVR filtered — However it is essential to note that UV filtering as a concept in preservation framing is comprised of 2 components. In this regard we must look at UV filtering as both:
Referring to UV filtration, it is imperative to know at what point in the spectrum 99% filtration occurs and where it begins to drop off. The best filtration is where 99% filtration occurs as close as possible to the visible light spectrum which starts at 400nm.
For example, Acrylite OP3 acrylic as used in all Gorilla Frames preservation frames, blocks 99.9% @380nm, then drops to 99.5% @ 390nm and so on. The goal is to achieve maximum filtration up to the edge of the visible light spectrum — filter above 400nm and you begin to filter out visible colors — begin filtration too low and you let UVR through to your artwork.
To put things into perspective, 99% UV filtration at 200nm will do little to protect your artwork, as 100% of UVR in the 200nm – 400nm range will endlessly bombard and damage your artwork.
The combination of deception and ignorance, from framers and manufacturers affects you in two ways: