I also have mustard I wanna clean....

I'm a bit surprised there is any mess in with the Papaver somniferum seed. How did you collect it? I just upend the dry heads in a paper bag and the seed falls out without any detritus. Otherwise I can only suggest a sieve.

If that is the only way I must but a smaller sieve ;P

Here you can see a band on whatever it is, and some reddish colored bits mixed in towards the bottom. All I did was turn them over, but the plants were infested with aphids? Though not the heads? Idk what it is, maybe it's still edible?

I usually just they the heads dry and then shake them over a bowl. Some debris does get in there but I find that window screening from Home depot is the perfect size to let the seeds through and not the chaff.

Wash them one poppy at a time with a very small brush and be sure to remove the stem. It is bitter.

I don't really understand your response, Emerogork. Why do you recommend washing the poppy heads? They are completely dry when the seed is ripe and holes open up in the top of the pod to release the seed. If you get them wet the seed will clump together and you are then going to have to dry it all over again. You only need to upend the pod in a paper bag. The stem isn't involved in the process at all, except as a handle to hold the pod upside down.

This is seed from Papaver somniferum shaken straight from the pods onto a sheet of paper and then put into a jar for storage. No other treatment is necessary if the seed is fully ripe and dry.