I want to know of methods (and devices) of selecting the biggest/heaviest bean and grain seeds from my garden, to re-sow the next season. I would like to hear from people that have done this, how they went about this, and if the results were satisfactory.
I have a few different crops of legumes (green beans, mung beans, peas - might try chickpeas, lentils etc. in future) and grains (maize, might try quinoa in future) that I have grown from heirloom seeds. The main idea with heirloom seeds is to have a perpetual cycle since one saves a few seeds at harvest, to sow again the next season.
Obviously, heirloom seeds are originally obtained from a commercial supplier or, better still, friend - which means the seeds were originally produced elsewhere where the climate, soil and other conditions may have been slightly different and perhaps your own garden might now be slightly less optimal. (I have still obtained satisfactory results until now, so this is not a big worry.)
On the other hand, it should be possible to improve your crops for your own local conditions by selecting seeds with the most desirable traits for resowing the next season, for at least a few generations. (My grandparents and parents were commercial papaya growers that grew their own seedlings for each year's plantation, so I have known about the concept - and practical application, even if not very advanced as judged by modern scientific methods - from an early age :-). )
With some crops (e.g. tomatoes and squash families) I would probably look at the fruits yielded and then take seeds from the most desirable ones. However, for legume and grain crops the part you eat is exactly the same as the seed, so my thinking is that the bigger the seed size, the more desirable.
Obviously, one would not take seed from only one fruit or one plant. Having seeds from a nice overall selection might help to maintain some genetic diversity.
With all this in mind: If I have a container of seeds (maybe 200 - 1000 seeds in total) what is a good way to separate and sort them by size? So that I can keep the biggest (say) 20% and eat the rest. Spreading them on a towel and eyeballing them, picking out some with tweezers, seems to be cheap, but very time consuming, labor intensive, and not very exact. Any better suggestion?
Added: I've also recently sprouted mung beans (for eating) and noticed that some kernels did not germinate; those seemed to be smaller than the successful ones (not a pleasant surprise on the teeth...) So perhaps this might be a consideration for removing the smallest (not completely developed) seeds from a harvest too.