HOW TO FRAME SOFT PASTELS
You need to frame pastel paintings behind glass, to avoid the painting to smudge. It also protects the painting of dust, insects or anything that could damage the painting. The painting should never touch the glass, as the pastel particles will stick to it.
By making sure the painting does not touch the glass, the artwork will be kept intact. As per the Tucson Pastel Society, you have to “allow at least a 0.125-inch space between the surface of the artwork and the inner side of the glass pane using a spacer or a mat.”
Source: Tucson Pastel Society: https://www.tucsonpastelsociety.org/framing.html
Do not touch the pastel painting. Just grab it from the edges. Even though the painting has been fixed, the pastel painting can still smudge. If you are framing the artwork yourself, when you have your frame with the mount, pick up the painting by the edges and place it facing down on top of the mount that is on top of the glass. It is better if you can have a double mount or some spacer, to allow any pastel particle that might fall, not dirty the mount. Also, the pastel will not be touching the glass. You will need to tape the painting to the mount, so it does not move. Use some archival tape, like a linen tape.
I tend to use 2 mm clear acrylic glazing instead of glass, this is because I carry paintings to exhibitions, and if I need to send a framed painting to a client. With glass, it will never make it in one piece. Plexi-glass is safer to use if you are going to ship the painting than regular glass. I know that the acrylic glazing could make the particles stick to the acrylic, but it is not usually the case for me, but maybe you should stick better to the glass recommendation, more if your artwork will be in your forever place!
Some people prefer to frame paintings with anti-glare glass. This goes with taste- some people think that the anti-glare glass darkens the colours.
Once your painting is framed, avoid putting them in line of direct sun. Also, do not put the painting facing down as the pastel particles can fall into the glass/acrylic.
The colours of pastels can last centuries. Compared to oils, they withstand the pass of time in better shape, as the oil can start to crackle, and colours look duller. If you protect your pastel painting, you can have it for a lifetime and for future generations!