For all types of glazing, if you’re not using a mat we’ll recommend a spacer to keep the glass off the art.
It’s the cheapest option but has the most disadvantages. It should only be used on pieces that have little monetary or sentimental value and you don’t care if they fade over time. People say “but my piece doesn’t hang in direct sunlight” when we recommend a UV filter. However, halogen, fluorescent, and other interior light sources contain harmful UV light, just not to the same level as sunlight. Here’s an example of fading caused by UV light.
Conservation Clear glass.
This is, from our perspective, the glass type that should be used on the majority of framed art. It is more expensive than Regular glass but has the highest level of UV protection (over 99%). The glass has a proprietary coating on one side that blocks over 99% of UV light is blocked. I does have the same amount of reflection as Regular glass.
It’s a little misleading because all glass has some amount of reflection but the proprietary coating on this glass does a great job in minimizing reflection – less than 1% light reflection. It also has the added benefit of a degree of UV Protection in that it filters 78% of UV rays. That’s not enough to be conservation quality but it’s better than nothing. The coating on A-R glass is obviously expensive to manufacture because there’s quite a jump in pricing from Conservation Clear.
The king of glass, Museum glass has a coating on each side – one for UV and one for reflection. They’re the same coatings used in Conservation Clear and Anti-Reflective meaning it has all the UV protection (over 99%) and the minimal light refection (less than 1%). Because of it’s 2 coatings it’s the most expensive of the glass options. Here’s a picture showing the reflection difference between Museum glass and Regular glass.
Glass vs Plexiglass (acrylic).
The same types of plexi (Regular, Conservation, Ant-Reflective, and Museum) are also available. I’ll talk about differences between plexi and glass in another post as well as the reasons to use one over the other.