Ultimat offer two upgrades for glass
This is identical in appearance to standard glass, but has a UV coating on one side of the glass, which prevents harmful UV rays from passing through to the artwork. As a result, the artwork is preserved from light damage for longer. Normal glass will reflect about 50% of UV light, whereas Conservation Glass reflects 98%.
Simply put, optical glass is the clearest picture framing glass available.
Not to be confused with terms such as non-reflective, and anti-glare, optical glass is in a different class. Standard non-reflective glass disperses light by having a pitted surface the disadvantage of this is that the quality of the image behind the glass degrades the further the glass is from the artwork.
Optical glass is an optically coated waterwhite float glass. The low iron content (when compared with standard framing glass) allows the true colours of the artwork to show through with no shift and whereas standard glass reflects back 5% of light, optical glass allows almost 100% of light to pass through. The optical coatings are applied to both sides and are identical to those of a camera lens and hence optical glass has a very low reflective quality which can, in certain hanging conditions, have the appearance that no glass is present in the frame!
In essence, just like any other piece of glass, optical glass protects your artwork from the elements, but unlike other types of glass, optical glass allows the full glory of the art to be seen, without colour shift, reflection or distortion.