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My pre-wet technique was all wet.
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Discussions > Coffee > Machines > My pre-wet...  
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chauncey
Senior Member


Joined: 10 Apr 2010
Posts: 37
Location: Portland, Oregon
Expertise: I love coffee

Grinder: Rancilio Rocky
Drip: Technivorm KBT-741, Coava...
Posted Sun Nov 21, 2010, 10:18pm
Subject: My pre-wet technique was all wet.
 

OK, so I stumbled across something in an unrelated post on Coffeed.com that totally changes everything I was doing, and it never would have dawned on me.

The general advice when using paper filters is to pre-rinse them with hot water to remove any paper taste, pre-wet the filter, heat the cone, etc.

I have been doing this for both Clever and Technivorm, BUT I have been draining the hot water THROUGH the filter, rather than pouring it out the top.  I thought I was being clever (no pun intended) by draining the hot water into my mug to pre-heat it, getting double use out of the hot water.

According to this post, this simple difference was adding 30 seconds to drawdown times on a Clever (and with the larger capacity TV, this difference could be even greater).  He speculates that the tiny floating paper fibers are clogging up the pores of the filters.  You can see those tiny bits floating about, so it may be an issue if they all gravitate to the bottom of the cone.

However, I suspect it is actually the pressure of the hot water rapidly passing through (and the exiting water creating a vacuum) which is compacting the fibers of the filter and substantially changing their permeability and pore size.  Indeed, you can see the filter getting forcibly "sucked" to the sides of the filter cone after the water has drained.  You'll see this makes sense if you think of the different rain protection you get from a highly lofted wool sweater vs. a boiled wool jacket or the reduced air flow you'd get through a fluffy furnace filter that had been flattened with an iron.

The hole-drained prewet is essentially tightening and preshrinking the pores as the fibers are uniformly sucked outward by rapidly flowing water, while the poured out prewet doesn't have this.  This isn't an issue in the second case once the coffee grounds are in the filter, because they act like a buffer that prevents excess vacuum pressure from clogging the filter--water trickles through the grounds at reduced flow rates and pressure, much the way tidal marshlands protect the mainland from a storm surge.

I couldn't believe something this seemingly insignificant as pouring vs. draining would change the brew so radically, but in my own findings it has been the case.    Lengthening your otherwise "standard" brew cycle by 10-15% is a recipe for over-extraction, as I was finding.  

I had been grappling with my extractions--using the standard ratios at suggested grinds was over-extracting--sometimes terribly and I thought I was doing something really wrong.  I kept grinding coarser and coarser trying to lower the extraction rate.  I was upping doses which helped somewhat, but 1) wasted coffee, 2) made a too strong (1.5% or more) albeit balanced brew needing dilution afterward and 3) made it likelier to get uneven extractions unless you agitated stirring/moving the grounds.  Any additional agitation quickly bumps up extraction rates and the more you do, the harder it is to replicate your techniques and results.  I had been chasing my tail on this because this clogging was messing with flow rates, dwell times, drawdown times and effectively kicking my extractions into another range altogether.

Sure enough, it turns out that this filter prewet technique was the big culprit--just changing that one thing moved some of my batches from badly overextracting to almost under-extracting.  Knowing this, I can now move away from my coarser grounds to more standard ratios and tweak my techniques with much finer control and already getting WAY better results.

I thought I would share this because it isn't something I would have ever suspected.  IN a nutshell, if you prewet: Pour your water into your cone with the valve closed, let it soak, then POUR IT OUT, don't drain it.

Hario V60 drippers with their huge opening and vortex are probably affected in a different way since you can't exactly pour out the top of something that drains about as fast as you pour into it.
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JKalpin
Senior Member
JKalpin
Joined: 28 Dec 2008
Posts: 822
Location: Thornhill, Ontario Canada
Expertise: I love coffee

Espresso: Aerobie Aeropress
Grinder: Baratza Maestro Plus
Vac Pot: Yama 5-Cup
Drip: Krups Moka Brew, BraZen
Roaster: Freshroast+8, Behmor 1600+
Posted Mon Nov 22, 2010, 6:56am
Subject: Re: My pre-wet technique was all wet.
 

chauncey Said:

I have been doing this for both Clever and Technivorm, BUT I have been draining the hot water THROUGH the filter, rather than pouring it out the top.  I thought I was being clever (no pun intended) by draining the hot water into my mug to pre-heat it, getting double use out of the hot water.

Posted November 21, 2010 link

Chauncey, the Clever makes a 9 oz mug +/- and the TV makes how much ...40 oz ...??

But the brew time should be about 4 or 5 minutes, with possible over-extraction if it goes on too long.

So how does that work, that you get 4 or 5 minutes, gravity feed, with both 9 oz or 40 oz?  Is it that you grind coarser with the TV?

 
Jerry
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chauncey
Senior Member


Joined: 10 Apr 2010
Posts: 37
Location: Portland, Oregon
Expertise: I love coffee

Grinder: Rancilio Rocky
Drip: Technivorm KBT-741, Coava...
Posted Mon Nov 22, 2010, 7:51am
Subject: Re: My pre-wet technique was all wet.
 

JKalpin Said:

Chauncey, the Clever makes a 9 oz mug +/- and the TV makes how much ...40 oz ...??

But the brew time should be about 4 or 5 minutes, with possible over-extraction if it goes on too long.

So how does that work, that you get 4 or 5 minutes, gravity feed, with both 9 oz or 40 oz?  Is it that you grind coarser with the TV?

Posted November 22, 2010 link

It's hard to compare them exactly because they are brewing different volumes.  Clever  has a much bigger aperture, so the drawdown phase has more to accomplish, but can take less time, while the TV is constantly draining through a smaller hole.  A similar-sized 12 oz batch on the TV might take only 3 minutes and would get less overall extraction than the Clever's immersion.  Inability to slow down small TV batches adequately is why I use the Clever on smaller volumes.

Clever basically gives you a couple more elements you directly control--vigor of initial pour, when to release.

The two do have different drawdown times and brew times--since clever is full immersion from the get-go, it  benefits from shorter overall brew cycle (which is good, because heat loss would start becoming an issue with the longer steep times).   I use the same grind for each method for convenience.  I adjust the grind to optimal for my TV, then accordingly adjust the time at which  I start the release phase  of "steep and release" with Clever.

I therefore think of my Clever as having grind size as a given (i.e. fixed) and a steep time that I can vary, while the TV as having a relatively fixed and steady delivery (all water is released into the cone in X minutes) with an overall brew time which can be altered by adjusting grind, extending the initial time the valve is closed, and how far the valve gets opened.  It is great to have controls at your disposal, but I try to fix as many variables as constants until the ones I'm adjusting aren't achieving the results.
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al_bongo
Senior Member


Joined: 26 Aug 2008
Posts: 455
Location: Scotland
Expertise: I love coffee

Espresso: Starbucks Barista
Grinder: Solis 166/Iberital MC2
Vac Pot: Cona
Drip: Chemex/Melitta
Posted Mon Nov 22, 2010, 7:59am
Subject: Re: My pre-wet technique was all wet.
 

I'm glad you found a solution to a problem you were having. The fibre theory clogging the pores is a simple straight forward theory. It doesn't mean it's true, but it is interesting.

Your theory/theories are, at best, wildly speculative. There is no vacuum created when water runs through a filter unless you are using a syphon. Wet paper sticks to things is a more straight forward explanation.
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JKalpin
Senior Member
JKalpin
Joined: 28 Dec 2008
Posts: 822
Location: Thornhill, Ontario Canada
Expertise: I love coffee

Espresso: Aerobie Aeropress
Grinder: Baratza Maestro Plus
Vac Pot: Yama 5-Cup
Drip: Krups Moka Brew, BraZen
Roaster: Freshroast+8, Behmor 1600+
Posted Mon Nov 22, 2010, 10:53am
Subject: Re: My pre-wet technique was all wet.
 

Chauncy, I concur with you that longer steep time can lead to over-extraction.  In my Krups Moka Brew, where extraction is under pressure, if I brew 36 oz it is completed in 5 minutes and is good, but 40 oz, completed in 6.5 min ...is not good.  In my case, brew time is water-volume-related.

Have you ever tried the two methods of wetting the filter and then filling the filter with water (no grounds) and timing the drawdown time, each way?  If there is a significant difference it will prove your theory.

If there is NOT a significant difference ...well ...you might wonder if it is fines from your grinder.

 
Jerry
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bodum_fanatic
Senior Member
bodum_fanatic
Joined: 19 Dec 2006
Posts: 481
Location: Missouri
Expertise: I live coffee

Espresso: Won't become one of those...
Grinder: Braun KMM30, Krups Fast...
Vac Pot: Never had much luck there.
Drip: Melitta Deluxe 132 made in...
Roaster: West Bend Poppery II
Posted Mon Nov 22, 2010, 3:15pm
Subject: Re: My pre-wet technique was all wet.
 

I've never been sure about the whole under/over extraction time with dry or pre-rinsed filters, though I find it hard to find anything wrong with the logic.  However, my understanding behind pre-rinsing the filters was to remover all the tiny bits of paper dust that could be trapped in the paper fibers from the manufacturing process.  With a full pot of coffee, I've never noticed any difference in taste, but with a little pour over device, there is a noticable difference to me.  Now, the whole deal with the flavor pores that Melitta came out with years ago, I don't know if I buy into that.  Yes, theoretically, the pores should allow more oils through the paper and into the brew.  However, once the grounds are wet, the pores are clogged anyway, and I just do not see how the theory translates to real world.  I've tried very hard to distinguish the difference in tastes between coffee brewed with and without pores in the filters (using both types of Melitta), in brewing different amounts, and I cannot tell.  Looks, smells, and tastes the same.  I did one time, however, pick up some cheap store brand filters that were made of thicker paper than the Melittas, and the steep time in my little pourover was about 20 seconds longer for a 16 ounce serving.  I still couldn't tell that it made that much, if any, differnece in the end result.  There is a point to which I believe the filter to be the least important part of the equation, at least compared to the quality of the water, the coffee, the grinder.
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maney
Senior Member


Joined: 27 Nov 2010
Posts: 4
Location: Chicagoland
Expertise: I love coffee

Posted Sun Nov 28, 2010, 8:31am
Subject: Re: My pre-wet technique was all wet.
 

Interesting food for thought... and experiment!

I've always had what seemed to be rather slow draining with the CCD, using both the brown and white Filtropa filters, rinsed or unrinsed.  I recall that I used to dump at least some of the rinse water out the top, but I think that was only the last bit, when the flow had slowed down.  I got accustomed to balancing the grind and the steep time against a drain that ran two minutes or longer.  Then I got around to trying the Bonmac bamboo filters.  Now I can grind ridiculously fine (11 to 13 on a Maestro, which is on the edge of what the manufacturer stakes out as the espresso range) and it drains in 60 seconds give or take not much.  And that's really drained, with under 50g retained where if there were only 60g left when I stopped with the Filtropa because it was getting on in time I counted it as a good one.  After about 50 brews with the Bonmacs, I'm still not certain I've got it quite dialed in, as I haven't gotten a bitter cup yet.  Granted the results are pleasing enough that I shy away from changing things again... [here comes the first of several cut scenes as stuff happens a.f.k.]

Ah, what's a Sunday morning without a little experimentation.  Ground the same bean I had last evening to the same setting (13), but with a Filtropa brown and backflushing rather than draining trhough the rinse/preheat water.  At two minutes drain time the grounds were still under a thin layer of liquid, and it measured right at 60g retained - good for a brown, not in the same ballpark as the Bonmac.    In the cup, it's much the same.  Breakfast is not the best time of day for making subtle judgements about coffee taste, but I'm not really noticing a big difference from the extra 3/4 minutes of water contact (I started the drain a little earlier, half expecting it would still be slow but not wanting to push too far in case a miracle occured).  Maybe a little more edge that could be due to more (over?) extraction, but it might be the woody note that others are much more bothered by than I seem to be, or perhaps even just the effect of 1/2 day more development (~36 hours since roast versus ~24).  All I can really say is that I didn't find any big, obvious differences.

...okay, there is something in the many-minutes later residual that I might describe as woody, or maybe resinous.  As if I didn't already know it, there's more to this.
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