Why not use the used ones? If you let them dry initially and then rinse them and dry them again they should be fine. The creative soul in me sees the possibilities. And if you used some food color dye as someone suggested or fabric dye even during the second drying phase this could get really really interesting! =) As far as washing it..I would say no. Its obvious to me that its an art piece. I would love to see it in person to awe over it and look at its every detail. =)