New answers tagged boil
There are a bunch of factors to consider here. To name a few: As you mention, zero to very little gravity will tend to increase the utilization rate as there will be less competitive inhibition from wort sugars. Boiling in water alone will mean a higher pH (as malt phosphates, even in extract brewing, would normally react with hardness in/added to the ...
This gunk is what's known as "trub", and it is proteins left over from the hot and cold breaks. The experiment conducted here: http://brulosophy.com/2014/06/02/the-great-trub-exbeeriment-results-are-in/ seems to show that it doesn't really matter whether it's included in the fermenter or not, but most people still remove it/don't add it.
It's hard to tell how fine the mesh is, but I think there'd be a good chance by the end of the boil, the metallic tea bag would be empty. In my experience, hop pellets end up dissolving into a sludge. The particulates are small enough that the tea bag may not contain them. I'd instead go with a fine mesh bag. Re-usable, cheaper, easier to clean.
As long as the total volume of the "tea bag" thing is sufficiently large for the hops and wort to mix freely I am sure its fine. Overall though its generally totally unnecessary to strip all the hop matter out. It will usually settle fine when fermentation is done.
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