Peter,
thanks for the update! Your experience with the filtering is exactly what I was afraid you'd go through. I've never made my own bitters, but I make tonic syrup and a cold-infused coffee concentrate, and both require many filter passes -- easily the worst part of the process. I use a combination of sieves and coffee filters (usually dirtying 3-4 sieves and using over a dozen filters) and while I have a routine, it's still incredibly involved and messy.
one hint that may or may not apply to bitters: BEFORE I begin infusion, I sift my solids through a sieve and discard any fines that fall through the sieve. For something like the tonic, this is a godsend as it's these fines that REALLY clogged up the coffee filter after infusion. By leaving those out, I'm left with only large pieces of cinchona bark, which a sieve easily takes out. If the ingredients for your bitters are ALL finely ground, then you're out of luck. Or if the grind is mostly fine, then sifting out the fines will be too wasteful.
I read
this thread and was tempted to get a similar setup, but it was very costly and, once I discovered pre-sifting, wasn't worth it. I also looked into various micropore cloth filter bags and such, but couldn't find food-safe specimens.
as for doling out bitters, I highly recommend investing in a few eyedropper bottles. The 1- or 2-oz sizes are perfect. I get incredibly tilted shaking bitters out of a dasher top, so every time I buy a new bottle, I decant it into an eyedropper bottle. I just find the dasher tops time-consuming and inconsistent.
in either case I think of 3 drops as being equal to 1 dash. I measured 9 drops into a 1/8 tsp (0.625ml) teaspoon and it was only half full, tops. I also tried 3 very hefty dashes from a Fee's bottle (relatively wide opening compared to, say, Angostura) and even that was less than a 1/4 tsp (1.25ml) teaspoon.
I've seen claims that a barspoon is roughly 1/4oz / 7.5ml / 1/2 tbsp, but not only is this untrue of any of my barspoons, but none of them match each other either.
if your bitters are relatively mild and you'll need a lot, all of what I said is unnecessary nittery, but I feel that for many commercial kinds of bitters, slight imprecision results in a wildly different result, given how concentrated they are.
Last edited by Mr. Farenheit; 12-14-2013 at 01:38 AM.