Darcie's ChalkFX is a specially formulated powder, meant to be used with Top Boss Watermark Ink.
When applied to a chalkboard surface, the image will remain in place until you decide to change it.
Just wipe off the image using a soft cloth, then wipe with a lightly moistened cloth.
You can then re-apply a different image to the chalkboard surface.
Darcie's stencils are meant to produce a "hand lettered" chalkboard look that you can easily change with the seasons.