Cleaning seed

What does "Properly cleaned seed" mean?

I guess it could mean removing the 'chaff', the other parts of a flower around a seed, but I think when it says that in plantfiles, a lot of the times they're talking about seeds that are in a fruit, like a tomato or blueberry. If they aren't "properly cleaned", any fruit mush that's left around the seed could mold easily and ruin them.

Okay! Thank You.
You can not clean chaff from all seeds can you?
I am having a hard time with Sweet Basil, Bachelor Buttons - to name a couple.

Some seeds are nearly impossible, and after a certain point removing every bit of chaff is pointless. I seem to remember critterologist describing collecting Basil seeds somewhere, I'll see if I can find it.
Batchelor buttons / Centaurea / Cornflower isn't too hard, as long as the seeds are developed fully and good and dry. Of course it helps to know what they look like - I could see crumbling a dried flower and wondering which part is a seed. It's like a tiny cylinder with a fuzzy white tuft at one end. Ther might be a picture on PF. I'll be back...

Okay, plantfiles has great pictures of Centaurea seeds:

http://davesgarden.com/guides/pf/showimage/85230/

And critterologist's post about Basil seeds. There's a link to her article about Basil there, too.

http://davesgarden.com/community/forums/p.php?pid=4077024

There is a whole forum about Saving Seeds here, I bet it gets busy this time year, too.

Those bachelor buttons might be easier to find than the gomphrena. I saw the pics on PF but when it gets right down to it the little cotton like pieces start looking like the dried flower.
Thanks for all your help.
Honey

Most daisy type flower/seeds have a little tuff attached to the seed and should be left on the seeds, this is natures way of blowing the seeds further away from the parent plants, like a little parachute type idea, other seeds are smooth either round or egg shaped, some flat some plumpish, all different sizes, I find to remove the chaff it is best done on a large piece of newspaper, on a flat surface, keep the seeds in a group, give a slight blow by mouth and some chaff will blow away from the group of seeds remove this with your hand, then repeat, after maybe half a dozen blows (depending how much chaff you start with) the seeds are as clean as you will get them, for seeds that are in a berry or like Holly etc, lay the berries onto kitchen paper to dry out a bit, then squeeze them from the outer pulpy berry, and dry the seeds some more, after that, you can normally rub off the excess pulp, remember, some plants need the seeds to be planted right away or they die when left for long periods of time. the library has good books on seed propagation and will give you so much advice on collecting, cleaning and most important, storing your gathered seeds. good luck with it, it is a cheep way to get new plants. WeeNel.

Thank you much. I will be making a trip to the library.
Honey