I have been thinking on the rerunning of heads and tails and have a question on the concept. I get that the congeners and other by products make the heads tails undesirable in a finished product. But if these compounds are so tough to separate in the first run, what would make it easier to pull the good alcohol out of subsequent runs. Does the additional alcohol in the next wash make the residual alcohol left in the feints easier to extract. Probably thinking too much but trying to make sense about all the processes and the chemical basis for each. B.

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Really these compounds are not that tough to seperate on the first run. Now if you dump them back in for the next pass through the still then there they come again and you still need to cut them out and throw them away that time.
If your collection the first pass through was not that good or you smeared the cuts then you may indeed get something from the next pass that you want to keep but-but-but ******** heads are heads and tails are tails no matter how you slice it. So if proper cuts and collections are made theres really no gain (IMHO) by running them through again, of course if thats what you want to do you certainly can."

From my read, it's just not that exact - the demarcation line is not always clearly defined between the various phases of the distillation run, and while similar, most runs are always a bit different - so one run it might be well segregated, another where some smearing happens and you want to clean it up, or a strip run, etc...

I have had a real porker I just tossed in the solvent jug, where others I thought were gonna end up that way aired out and were better, yet, I reran them any way to clarify it. Mostly because I was rushing in the first run. As heeler has indicated on a cleanly cut batch, heads/tails are just that. Some tails might be used for blending for a flavor profile (from a pot run).. all depends. ... This is the natural part we scientists just marvel at