Have the second "experimental" batch on tap. The first was low Ca, Brewtan B, Irish moss, careful trub separation; the second, increased Ca and none of the rest.
Observations: As had been the case of late, the first batch had turbidity noticeable in the glass without any special effort, while the second appears brilliant in the glass. It is not filtration-level clarity, there is some turbidity apparent using a makeshift light box (card with a slit and LED source behind) -- at 90° this is intermediate between two comparisons, Great Lakes Dortmunder Gold and Miller High Life. The first batch was noticeably hazier than the Dort. Only my filtered beers have been clearer than the second batch, and this is the level of clarity regularly achieved before I started with the BTB. The second batch perhaps shows slightly more bitterness, but I'm not ready to relate this to trub carryover, since the hops were from a fresher lot.
My takeaways:
• Calcium is still the closest thing to magic dust in brewing. If you choose to use BTB, you should be aware of its chelation of calcium and adjust accordingly.
• Further study has taught me that BTB has no inherent antioxidant properties, but only forestalls oxidation through chelation of the catalyst, iron. Since I am using RO water with no iron, this function is irrelevant.
• This leaves Brewtan B's other possible function to consider, that is, its function as a kettle coagulent. This experiment, as with others, indicates no detrimental effects from trub carryover as pertains to clarity of the beer; fermentation may be enhanced, and the jury's still out on flavor.
As for me, in subsequent brews I've been incrementally increasing calcium to levels I have found beneficial in the past. I may use Irish moss and minimize trub just to have cleaner harvested yeast, or not. I see no need for Brewtan B in my brewery, it is not really helpful in achieving clarity (or, in case of my water, even potentially increased flavor stability.) Hopefully I will not see a need to return to filtering. (A yeast that drops better than 2124 would probably clear everything up. Literally.)