Storing pastel paintings layered on a shelf, in a large drawer, in print
racks or bristol board folders can be a problem especially when you
need to go back through the stack to find a certain piece.
Use glassine or tracing paper to cover the pastel. The artwork must be lying flat with the pastel side facing up. Cover the piece with either kind of protective paper and use drafting tape (3M, no 230C) to keep it attached to the pastel work.
A tab with the name, size and other pertinent information can help locate a work without having to sort through every piece. The tab can be either a pH-balanced piece of paper laid over the glassine and allowed to protrude or it can be attached to one edge of the glassine for each painting, much like you would do with a school notebook.
Using the thinnest version of pH-balanced foam core board or other non-acid or archival board in the layering process, along with glassine, helps keep the weight of unevenly stacked or slightly different sized paper more evenly distributed. Use interleaving boards that are all the same size and slightly larger than the largest painting paper you are storing. Interleave each piece wiith glassine and board or use the board every 2, 3 or 4 pieces.