On Saturday evening, I set out on an elusive chase to identify potential taste contamination stemming from my brewing equipment. I taste-tested my pour over brewing kit with boiled, Brita-filtered water.
The results were surprising.
I tested twice: once on a well-used K250 V60 filter and once on a new filter. In each case, I used a Hario Buono pouring kettle, a Copco Fusion boiling kettle and a glass V60. Drinking containers were glass or ceramic. Each pour wetted the entire filter in a circular motion.
Tasters: myself (Nate), my lovely wife and Katherine Hartline of Trabant / Mercanta
Each test used three separate cups:
1. First pour through a dry, room temp filter. Approx. 12 oz.
2. Second pour immediately after first through the same filter. Approx. 8-12 oz
3. Third pour straight into a drinking container as a control. My Hario tended to run out of water about this point, so after about 4 oz of Hario water I topped up from the Copco.
In each case, we observed the surface of the water for visible oils and tasted the three cups (not blind).
For the used filter, the first pour revealed substantial floating oils, a slight coffee taste and a metallic taste. Pour two yielded very little oil, no coffee taste, and a hint of metal. The slight acridity of the metal seemed to balance the sweetness of the Brita. Pour three revealed a distinct metallic taste, somewhere between the first two pours. All three of us preferred the second cup.
For the new filter, results were similar, without the complicating factor of the coffee. Again, we preferred cup two.
What does this mean? Instinctively, I'd suggest it means that a pre-rinse immediately before brewing and minimal dwell time in the kettle are both key factors for minimizing hints of metallic contamination in the brew. While I'd kept brew time minimal before the experiment, I had also been failing to pre-rinse, so these results suggested a change in routine. Since the experiment, I've incorporated a pre-rinse into a couple of brews and found no discernible metal taste.
Of course, these results aren't bullet-proof. For one thing, using Brita water simplified the problem by taking the vexing variable of dissolved solids out of the equation. We also didn't get into the effect of cleaning methods / products or the hairy question of taster's bias, which is a particularly pesky ghost in the machine.
Despite uncovering some new questions, we were able to uncover some reasonably definitive results that changed the way we brew. Here's to incremental improvement!