It is necessary to protect pastels under glass to avoid them to be smudged, scratched or to gather dust (I am talking here about soft pastels, not oil pastels).
I have seen two different types of framing styles for pastels. This is a matter of personal taste:
- Frame with a mount: this works well with all sorts of pastel styles. You frame the pastel as you would do for a charcoal drawing or a watercolour.
- Frame without mount: This method is really effective with pastel paintings that use painterly effects similar to oil paintings. You basically use the same style of frames that you would for an oil painting, the difference being that you need a glass.
Think about whether you want to use UV glass or not. It really depends on where the work is going to be hung. UV glass is more expensive and you will need to take that into account when setting your price.
Avoid acrylic sheeting because its static charge could lift the pastel dust. In addition, if you use large thin sheets of acrylic, it will bow and touch the surface of the pastel.
Make sure that the pastel does not touch the glass. Allow at least ¼ inch space between the surface of the work and the inner side of the glass pane. A mount will serve this purpose or, if you want to frame you pastel like an oil painting, you will need to insert a separator between the glass and the work.
A small amount of pastel dust is unavoidable and the best way to prevent this ruining your framing is to create a gutter where the dust can fall and settle out of sight. The illustration below shows a section of a frame sandwich and demonstrate how it is done.
It is recommended to use archival or acid free material for the backing and the mount (acidity can cause discoloration in the long term and damage the paper).
When transporting your work, avoid turning any pastel face-down. Even if you apply fixative to your work and gently tap the back of it before framing, there will always be a small amount of pastel dust likely to fall from the surface of the composition. The last thing you want is having grains of pastel dust on the glass or the mount and have to re-open the frame to clean them.
Finally, Paul Dorrell, wrote an excellent article titled “The Business of Archival Practices”. He suggests putting on a back of any work that can be damaged by UV rays a “Warning Labels” telling buyers not to hang the work in direct sunlight. His comment on this (and he is a seasoned gallery owner) is: “I realize this seems obvious, but not everyone gives thought to these issues.”
The Business of Archival Practices by Paul Dorrell