Harshness - How much alkalinity is too much?

I agree with Jeff; first thing I thought when I read this was “yeast bite”.

Alcohol has a hotness and a bitterness when young.  Could be part of it; harshness and bitterness are related.  2-3 weeks is pretty quick for trying to drink 8.3% beers.  If you want to know what alcohol bitterness tastes like, take a light lager and add some vodka to it.

I question the level of carbonates in your water.  I think I’d use relatively soft water for the dubble and relatively soft water with added gypsum for the saison.  But it’s not my recipe, so I don’t know what it’s supposed to taste like.

Maybe it’s me, but I think people mess with their water way too much.  If your beer tastes like alka-seltzer, your spreadsheet is leading you astray.  Seems like a big percentage of the beers I tasted at the NHC had this kind of a flavor to them.

So my guess is that you’re getting the combined effects of three or four different things going on at once.

And that’s some serious attenuation, by the way…