« on: February 21, 2011, 09:48:10 PM »
So, I've been thinking, and trying to tease out variables that have changed since I started getting the astringency. I've done 20+ batches of BIAB without this issue, all of varied gravity, with the same techniques (squeezing, water treatment, decoction mashing, etc). To summarize:
1) Switched to a poly paint strainer bag instead of cheesecloth.
2) Switched to pre-milled grain instead of milled-at-home grain.
3) I used to filter out the hops/break material going from the kettle to the fermenter, but haven't recently. Lately I've just dumped it all in, at the advice of quite a few people who say that it doesn't make a difference.
The possible differences that has made are:
1) More small particles getting into the wort. This seems to be confirmed by me seeing more grain bits floating to the top of the wort before the boil really gets going. I skim as much off as I can, but I can't get it all off.
2) More flour in the grist to begin with, so maybe that contributes to the particulates.
3) Maybe the hops in the colander acted as a filter to strain break material and grain bits from the wort.
So of the variables that I know have changed (not including variables I don't know I've changed) it seems that particulate matter in the wort is the most likely culprit. Does this sound correct?
Maybe squeezing the bag can cause astringency in some cases, and maybe I've just gotten really lucky in the past when I haven't had this problem when squeezing. And if squeezing does cause astringency, would it be because of the excessive particulates in the wort, or is there some other factor to this?
On a side-note, can anyone describe the mesh-size difference between cheesecloth and voile? I know my paint strainer bag is coarser than cheesecloth, but I haven't seen voile, and I know that's what most BIAB guys recommend using.