brew troubleshooting...a ramble and a riddle

First off, a riddle:

You have an old time balance scale (see pic) and 8 balls of all the same size...no difference except one weighs less than the others. You can use the scale twice, no more. How do you definitively figure out which ball weighs the less? Answer at the very bottom:



So, I have a dry stout that tastes sour...kinda plastic-like...very unappealing. I used irish yeast and was afraid I had a bad yeast ester thing going on, but it was too strong a taste. So I took it to the LHBS to give them a taste. They picked it up as well and said most likely culprit was water chemistry. I also have a Nalgene bottle that I keep filled up with pre-boiled water that I didnt think to mention while at the shop.

Spoiler alert: I have three scenarios to check: 1) brew with pure RO water and build up a profile 2) brew with straight tap water 3) water isnt the problem, its the nalgene that is throwing the off-flavor. I plan on making two half batches using 1 and 2, if neither are the problem, it's curtains for my nalgene bottle.





















Answer to the riddle:
you pick 3 balls for one side of the scale, 3 for the other. If they weigh the same, you put the other 2 balls on the scale, one to each side.
IF they do not weigh the same, you take the three from the lighter side, pick 2 and weigh them. If they are different, you found the lighter. If they are the same, the one you didnt put on there is the culprit.

Can't help with the nalgene because Ive never used it, but I like the riddle

If you can detect a plastic taste in a dry stout, then I think I need to have my taste buds replaced.

-a.

tangent... but *you* started it.

You told the riddle with eight balls but you could have asked with nine balls and 2 weighings.

Or did you think the number 9 (3 squared; essential) would have made the puzzle obvious whereas 8 (being 2 to the 3; irrelevant) would be misleading?


Actually, the riddle gets kind of impressive with big numbers. Example: Find the the one imperfect ball out of 27 in 3 weighings. Or find the one imperfect ball out of 81 in 4 weighings. Or find the one imperfect ball out of 243 in 5 weighings. It's a tertiary sort rather than a binary search. Each bit ("trit"???) of information gives you one of *three* possible outcomes (light, heavy, even) as opposed to the binary sort's two (on, off). You can in n weighings you can have 3 to the n power of outcomes, which significantly begins to outperform the standard binary 2 to n power of outcomes. The binary outcomes are amazing enough (just think what your computer does with 0s and 1s) but a tertiary (0, 1, -1) would leave it in the dust.

Imagine someone asking you to find the one single misweighted ball out of 59,000 and you telling them you could find it in only 10 weighings. (Of course the scale would have to be large enough to hold 19,667 balls in a cup and then be sensitive enough to measure the difference in weight between 19,667 normal balls and 19,667 balls where all but one are normal...)

Click and Clack did a similar riddle on Car Talk a month or so ago. I didn't get it right then either..........
Not sure from your post: are you using city tap water? If so, are you treating to remove chlorine and chloramine? Other posts I've read indicate that a plastic band-aid like flavor can be due to chloramine.
If you're OK there, then having the water tested by Ward Lab(or another reputable lab) is a good idea, and the only sure way of knowing what you have to work with.