2.Weight(heavyvs.lightanddifferencesinspecificgravityand surface area). This separation is best done with a box fan, an air column or aspirator (see equipment section). These work bypassing a stream of air past the seed allowing the light (often unviable) seed to be blown out of the seed lot. This method will also remove any light chaff that remains within the seed lot.
3. Shape (round vs. non-round). This separation can be done with a spiral separator (round seeds will roll faster than flat or non-round seeds).
4. Surface Texture (rough, smooth or pointed). A flat piece of roughed-up cardboard works well for this separation. Round seed will roll to the bottom when placed at a slight angle while flat seed will be “caught” on the roughed cardboard. Also a velvet roller works well (see equipment section).
5. Color: This separation is most often done by hand-picking although there are color separation devices; they are not commonly used by small-scale seed producers.