Should You Rinse Your Paper Filters Before Brewing?

Should You Rinse Your Paper Filters Before Brewing?

We put the question to the test.
by Maciej Kasperowicz | July 22, 2020

If you go a-searchin’ for pour over recipes on the internet, you’ll find plenty that tell you to rinse out your paper filters before brewing, because you don’t want your coffee to taste like paper. Since I brewed my first Clever Coffee Dripper a decade ago until some time last year, I rinsed basically every filter I brewed with. And then, hearing some chatter on coffee Twitter that rinsing was falling out of style, I tried brewing a Kalita Wave without the rinse, and realized I couldn’t taste paper at all!

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For this article, however, I thought some more thorough taste-testing (or as thorough as is possible under social distancing) might be required. So, I did some brewing and tasting with my Wave, while taking the thicker-filtered Chemex along for the ride.

Putting Rinsed Filters to the Taste Test

I tried a similar taste test on both the Kalita Wave and the Chemex, using white (aka oxygen-bleached) filters for both. First, I tasted the water itself. I poured the same amount of water I would use for a representative batch (that was 320 milliliters for the Wave and 560 milliliters for the Chemex) through the filter and set it aside in a mug.

Then, I poured the same amount of water through the already rinsed filter. I only have one Wave and one Chemex, so in order to get the coffees to a similar temperature for tasting, I poured off a tiny bit of the more recently poured water into a cupping bowl and let it sit for a while. Since a smaller mass of liquid will cool faster, that smaller sample eventually cooled to the same temperature as the first sample, which was hanging out in the mug.

For both the Wave and the Chemex, I couldn’t taste a real difference in the water poured through the dry filters and the water poured through the pre-wet filters. Since I couldn’t taste the difference in the water itself, I found it pretty unlikely that I could taste it once we got some tasty coffee solubles in that water. Still, I wanted to taste for sure, and check a few other things as well.

Even if rinsing out paper filters (or at least these two particular kinds of paper filters) doesn’t affect flavor, it’s still possibly wrong to say that it doesn’t affect brewing. First of all, we often think of the rinse as having a double function of pre-heating the brewer, so it’s better able to maintain its brew temperature throughout.

Secondly, even if using unrinsed filters doesn’t increase papery flavor, we might expect having a rinsed, wet filter to change something about the amount of resistance the filter provides and how our pour over flows through.

As far as temperature, I was surprised to find that pre-heating didn’t make a significant difference in either the Wave or the Chemex. I used an instant-read thermometer to measure the temperature of the slurry (the mixture of coffee and water) throughout the brew and found the readings pretty much the same. I guess the act of pouring hot water during brewing warms both brewers enough.

To test flow rate, I tried to pour as similarly as possible whether brewing with or without a pre-rinse. With the Chemex, the filter acted pretty much exactly the same, with the batches all finishing draining within five seconds of each other. For the Wave, the pre-rinsed filter did let the coffee through a little faster (around 15 to 20 seconds, to be exact).

I once again got the coffees to cool to a similar temperature and tasted them against each other. The Chemex brews were pretty much indistinguishable and there was certainly no paper-taste to be found. For the Waves, I could actually taste a difference. The coffees brewed with the unrinsed filters didn’t have any flavors that I could recognize as papery, but the rinsed filters did taste noticeably different — a touch fruitier and brighter. I’m pretty sure, however, that this was due not to any papery taste getting in the way, but rather due to that 20 second difference in brew time. Indeed, when I poured a little quicker into an unrinsed filter, those fruit notes came back.

So, I’m officially done rinsing white pour over filters. Do I want to do these experiments again when I’m back in an office and can have my co-workers set up some truly blind tastings to make sure? Absolutely. Am I going to buy some brown Melitta filters and run separate taste tests on those? Yup. But I see no reason to recommend you rinse out your bleached Kalita filters or Chemex filters. Save a few seconds to think about something pleasant!

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