Yesterday, I packaged up two small pastel paintings to ship USPS Priority Mail to the East Coast. If you sell your unframed pastels through DailyPaintworks (or similar site) you might be interested in knowing how I do this since it has been a successful shipping method for me for national and international sales.
2. Carefully slide the painting into an 8-7/16 x 10-1/4 inch poly sleeve (Impact Images B108).
3. Cut two 9x12 inch pieces of foam core.
4. Remove the protective strip from the flap of the poly sleeve and attach the sleeve (with painting inside) to one piece of foam core. Not show here is a small piece of tape I apply at the bottom edge of the poly sleeve to secure it to the foam core.
5. Cut foam core strips that that will act as a mat (they won't touch the pasteled area) and attach them to the second piece of foam core. When this "lid" is flipped over onto the painting and secured with tape at all four sides, it makes a great protective package. Keep in mind that I work on relatively fine toothed sanded pastel paper and my paintings don't shed much pastel particles/dust. If you work on a coarser tooth with a heavier application of pastel, you may want to eliminate the poly sleeve so nothing touches your pastel in shipment.
Duck brand Stretch Wrap. Then bubble wrap for shock protection, then a plastic bag for waterproofing. Air filled "pillows" go into the Med flat rate box then the painting then more air pillows, seal it up, label and mail. Voila!