A small overview
When you look at a picture, you want to view it undisturbed. Because hardly anything can be as disturbing as reflections in the glass surface. Therefore, glass is of enormous importance in framing. It stands between the picture and its viewer. Its tasks are manifold, ranging from protection against dust and contact to UV protection for the picture.
But not all glass is the same. The market offers a variety of different glasses with different properties and prices. Basically, there are mineral glasses - also called real glass - or glasses made of plastic such as acrylic glass. We offer only high quality acrylic glass. Besides the material, the surface has a great influence on the properties. Cheap glossy glasses often reflect strongly, and frosted glasses make colors look duller. Only high-quality interference-optically anti-reflective glass - also known as museum glass - offers an almost reflection-free view with the best color rendition. But these glasses are also very popular in private homes. We explain what's behind them.
What is museum glass?
Museum glass is the synonym in German-speaking countries for interference-optical anti-reflective glass. The glass is completely transparent and the image can be viewed true to the original. "Anti-reflective" glass is thus the optimal solution for unclouded art enjoyment and meets the highest demands. We have been observing a steady trend towards anti-reflective glasses for years. The best-known manufacturers are SCHOTT with its Mirogard series, Groglass with its Artglass series of mineral glasses, and Tru Vue with its Optium Museum Acrylic® acrylic glass, among others. But what is behind the term interference optical anyway?
Reflection-free due to counter-propagating light waves
In interference optical antireflection coating, the base material (usually real or acrylic glass) is coated with a large number of invisible layers of metal oxide only a few μm thick, each of which reflects a different waveband of light.
They prevent reflections by the physical effect of destructive interference of light waves. Depending on the length and energy of the reflected waves, the light waves traveling in opposite directions cancel each other out. Similar to an eyeglass lens, the glass surface remains smooth and reflections are reduced to less than 1% by the coating. The glass is completely transparent and the image can be viewed faithfully. "Anti-reflective" glasses are the optimal solution for unclouded enjoyment of art and meet the highest demands. The prerequisite is lighting at an acute angle. Windows opposite the picture are not ideal.
Another advantage - high UV protection
Papers are particularly sensitive to light, especially UV light, which can cause severe damage in the long term. Even despite LED lighting, which is free of UV radiation, high UV protection of the glass is still very important.
The museum glass that we use has such protection. While normal glass blocks only about 45% of UV light, Optium Museum Acrylic and Artglass AR 99 Protect protect over 99%.
MIROGARD becomes ARTGLASS
Our previous glass manufacturer SCHOTT has stopped the production of its Mirogard series. Therefore, as soon as our stock is depleted, all frames will be delivered with the respective comparable glass from Artglass. Artglass is the product line of the Latvian glass manufacturer Groglass, which is now the leading supplier of anti-reflective picture frame glass in Europe. The quality of Artglass is at least equal to that of Mirogard. The colors of the residual reflection correspond to those of Mirogard. You as a customer even benefit from a higher UV protection.
The following grades are available (the respective number stands for the UV protection in %):
· Artglass AR 70 replaces Mirogard
· Artglass AR 92 replaces Mirogard Plus
· Artglass AR 99 Protect replaces Mirogard Protect
The main difference between SCHOTT Mirogard and Artglass by Groglass is the coating process. While SCHOTT coats its glass in a dipping process and then bakes it in the oven, Groglass vaporizes its glass using the so-called sputtering process. Here, the metals are vaporized by plasma in a vacuum chamber and then deposit as a wafer-thin layer on the glass and bond indissolubly with the surface.
Groglass says its advantages are lower energy consumption and more stable quality due to fewer coating defects. The surfaces are mechanically and chemically tested for resistance. The advantages of Artglass are higher UV protection and very good maintenance properties due to a very smooth and insensitive surface.