Watercolours and pastel pictures are framed in different ways as determined by the different methods by which they are created.
Watercolours need to be protected and encased by glazing with a mount that keeps the artwork away from the glass.
Pastels & Chalk pictures are particularly fragile, and require careful handling. It is the artist's job to apply a fixative, should it be required. The application of a fixative can alter the appearance of the picture so as a framer I do not carry out this process. I always use glass when framing pastels as the static created by acrylics or plastics can cause damage. The addition of a 'gutter' mount both increases the distance of the picture from the glass and helps keep the bevel clean, migrating pigments fall behind.