Thoughts on using a double bloom for pour-over

Coffee preparation techniques besides espresso like pourover.

#1: Post by bobR »

I don't claim any of these comments are technically accurate. They are just my thoughts and observations for anyone interested. I was seeing inconsistency in brew time and taste within individual coffee batches (bags). I was being very meticulous with procedures. Then I noticed as the coffee aged the brew time generally dropped but then came back up when I refilled my daily stock from the freezer (into an Atmos vacuum container from the SAME COFFEE BAG). This phenomenon repeated itself. I started to suspect that the degassing was more vigorous at the start and then over 1-1/2 to 2 weeks in the Atmos container dropped some. I guessed that the high volume of degassing even with a regular bloom was both decreasing extraction and interfering with the drawdown rate. Maybe CO2 rising out of the bed was slowing drawdown???

I saw an article by David Train of April Coffee Roasters in Denmark who was using a double bloom technique for competitions in order to "promote a more even extraction". With my normal bloom of 40 seconds with swirl, the bubbling stopped but with my first regular pour I saw a large amount of additional degassing. A fair amount of CO2 seems to be trapped in the coffee cake after the first bloom. I think this is pretty typical. I think that the second degassing can vary based on coffee age and just how much degassing has naturally occurred already.

So I tried a double bloom technique trying to balance between effectiveness and using the smallest amount of water possible to prevent much water from passing though into the cup. So, for 21 grams coffee I started with 40 grams water, swirl. At 35 seconds I added 25 grams water, swirl. At 55 seconds I started the first regular pour. My first regular pour had very little additional degassing. I observed much better brew time consistency and taste over time and the fastest drawdowns (brew times, taking into account the longer total bloom time). I totally realize you can get great results with one bloom (or even no bloom techniques) but I think this very high efficiency double bloom might give better consistency. The inconsistency as I mentioned can come from your coffee aging at home or even the time from roast delivery from the roaster.

I was brewing an Ethiopian Natural coffee from Klatch using a V60. 21 grams coffee, 300 grams water. 2:35-2:40 brew time with the 15 second longer bloom included. Medium-fine grind using a Comandante grinder (17.5 clicks, 35 clicks using red axle).

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#2: Post by MB »

Tried it twice today with nice results. Haven't done a side by side comparison nor enough cups to be anywhere near definitive, but certainly worth continuing. The overall time was more on the first cup, so I slightly loosened the grind on the second cup for a tasty result.
LMWDP #472


#3: Post by MikeTheBlueCow »

I absolutely have done double blooms for very fresh, gassy coffees. However, recently I have just been doing a single 60 second bloom and I feel this might work very similarly. Kubomi, 3-4x bloom. I've had very consistent draw downs. In the end our blooms don't look much different, because you're using about the same amount of water and the same total bloom time - so I might just try doing it your way and seeing if there's a difference to me, but my coffee right now is not very gassy so I wonder if I'll notice anything different. I do find the kubomi prep is very important for me.

bobR (original poster)

#4: Post by bobR (original poster) replying to MikeTheBlueCow »

Yes, any way you can get an effective degassing (bloom) with minimal excess water passing into the cup, the more consistent results you'll get in my opinion. I base the effectiveness on how much degassing is apparent on my first larger pour. I want to see very little if any bubbling. I do use a well in the grounds but not specifically the Kubomi technique. I'll try it and see the difference. I just don't want to go back to wetting the grounds with 2X the water amount and waiting some time period.


#5: Post by MikeTheBlueCow »

So I did just try it and for me, I had an issue with waiting 40 seconds until the second bloom pour because my second bloom didn't drain before my first large pour. I used to do 30 seconds then second bloom pour. I still agree two blooms are typically useful for gassier coffees, but for me it's not needed for the average coffee past a certain freshness, as long as I keep the 60 second bloom.


#6: Post by Jonk »

I have been using the 2 minute total double bloom that Hedrick demonstrated in his Kono video since then. Can't say there's a massive difference in flavor (haven't even tried to compare) but I do like just how consistent the brews seem to be. Even across different beans, grinders and settings it seems to have some equalizing effect.