Water ratio for a percolator

Coffee preparation techniques besides espresso like pourover.
BaristaMcBob

#1: Post by BaristaMcBob »

Is the water ratio for a percolator basically the same as for a pour over? That is, something in the order of 1:15 to 1:17?

Nunas
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#2: Post by Nunas »

Anywhere from one to four teaspoons per cup/mug of water, depending on how strong you like your coffee. But...OMG...does anyone still use a perk? I thought they went out with buggy whips, the Edsel and hula-hoops :lol: I have not used a perk since camping as a teenager (I'm in my 70s :wink: )

BaristaMcBob (original poster)

#3: Post by BaristaMcBob (original poster) »

Haha - yeah, a perc is not as cool as a Chemex - but it makes a good brew, turns itself off, and keeps the coffee warm. You can even put it on a timer. You wonder if anyone still uses one - whereas I wonder why everyone isn't using one :)

All you need is the correct grind and water volume - which is what I'm looking to find out. I try not to think in terms of "scoops" or "mugs" since those units are non-standard. I normally do all my preparation in grams and mls.

jpender

#4: Post by jpender »

I bought a percolator about six years ago to play around with. I'd read that they can make good coffee.

Given how they work I think it makes a little more sense to think of them as an immersion brewer rather than a percolation brewer like a Chemex. That is, the liquid in the grounds will be at the same strength as the free liquid you drink. In a Chemex the liquid trapped in the grounds is closer to being fresh water. That would affect the ratio you choose, assuming you have one in mind to start with. Basically you'd just use a ratio about 2 less than a pour over ratio, to account for the retained water of roughly 2 grams per gram of dry grounds. In other words, if you like it at 1:15 with a Chemex then maybe try 1:13 with a percolator.

My own percolator brews didn't turn out very well. I'm not really sure why. After brewing with it for a little while I donated it to Goodwill.

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yakster
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#5: Post by yakster »

Perc pots work great at altitude where water boils at a cooler temperature, I hear.

Because of the recirculation, the coffee is usually well extracted so you may end up using less coffee than normal.
-Chris

LMWDP # 272

BaristaMcBob (original poster)

#6: Post by BaristaMcBob (original poster) »

I get what you're saying, but did you mean 1:17 in your example, not 1:13?

jpender

#7: Post by jpender »

Let's say you have a pour over that's 1:15, e.g. 10g of coffee and 150g of water. About 2x10g of water is retained in grounds so you have about 130g of water in the cup.

If you make an immersion brew and want it to be the same strength, and you get the same extraction percentage, then you'll want the dissolved solids in 130g of water just like with the pour over. But in the case of immersion that includes the water in the grounds too. So you'll want 130g of water total, or 1:13.

BaristaMcBob (original poster)

#8: Post by BaristaMcBob (original poster) »

Does it, though? With 150g of water going in, I would get 130g of liquid coming out, regardless of whether it's a pour over or immersion.

DamianWarS
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#9: Post by DamianWarS » replying to BaristaMcBob »

both immersion and percolation have trapped liquid in the coffee bed called interstitial fluid but the TDS of these trapped liquids are different. Scott Rao wrote a blog of some of the differences between these brews and how extraction works with them.

when it comes to extraction with immersion there is an initial concentration gradient that over time will balance itself with the rest of the water and it will all be of the same strength, this is called diffusion. Convection and agitation can help speed this process up but if you were to check the TDS of the top of a french press and the TDS at the bottom of a french press where the grinds are they will be pretty close. The bottom probably will be slightly higher but over enough time through the process of diffusion, it will balance itself through the entire french press. This is like dropping a few drops of food coloring in water, first, you distinctively see the color swirling throughout the water but over time the entire water will become the same colored hue and that's pretty much how immersion works

with percolation it's different. clean water is constantly poured over a bed of coffee, washing away coffee solubles and then repeating it with more clean water. if you were to check the TDS of percolation after the brew the TDS of the cup will be far greater than the TDS of the interstitial fluid in the coffee bed because the solubles should be depleted and the TDS should be very low.

although the yield for both percolation and immersion may be the same (150g in, 130g out) the extraction is different. with percolation there is 20g of water trapped in the coffee bed at a much lower TDS than the cup, with immersion, there also is 20g of trapped liquid in the coffee bed but at the same TDS (or very close to) as the cup. So in practice, you should calculate the TDS of the brewed weight with percolation but with immersion, you should factor in the total water weight when calculating TDS for example:

EDIT: Please note the EY% formula I used here is simplified and it does not factor in the added weight of TDS. Please do not use this for calculating EY%, it's stated here to demonstrate extraction differences between percolation and immersion brewing only.

Percolation
EY% = TDS x brew weight / dry coffee weight

Immersion
EY% = TDS x total water weight / dry coffee weight

if TDS is 1.5 then....

Percolation
EY% = 1.5 x 130 / 10
EY% = 19.5%

Immersion
EY% = 1.5 x 150 / 10
EY% = 22.5% :shock:

so you start with the same weight of coffee, use the same amount of water, and end up with the same weight in the cup but the immersion has a higher extraction than the percolation. So to balance this, you add more coffee to the immersion.

Extraction Goal = 19.5%
1.5 x 150 / 19.5 = new dry coffee weight
new dry coffee weight = 11.5

Immersion
EY% = 1.5 x 150 / 11.5
EY% = 19.5

another way of doing it would be to use less water, instead of using 150g of water for the immersion use 130g. your yield would be lower (aprox 110) but the EY would be matched with the percolation (it's in fact the same equation of the percolation)

EY% = 1.5 x 130 / 10
EY% = 19.5

So we moved from a 1:15 ratio to a 1:13 ratio.

this is not perfect as it assumes the TDS of the interstitial fluid of percolation is 0 which may be very low but it should be more than 0 but this is the justification of why you would go from 1:15 to 1:13 with immersion to get the same extraction of a 1:15 with percolation.

with a percolator it's not clean water going through the coffee bed it's recirculated water and I think I would agree that this would make an effect similar to diffusion that the strength of the coffee bed will remain the same as the strength as the brewed coffee because any trapped liquid in the coffee bed would be the same strength as the brewed coffee (since it's just the brewed coffee recirculated) so if you do 1:15 with a pourover 1:13 may be justified with a percolator.

jpender

#10: Post by jpender »

BaristaMcBob wrote:Does it, though? With 150g of water going in, I would get 130g of liquid coming out, regardless of whether it's a pour over or immersion.
That's true. But if the extraction is the same then the strength will be lower for immersion because the dissolved solids are also in the liquid trapped in the grounds. With percolation that liquid is closer to being like water. On the other hand, if the strength is the same then it means the extraction was higher in the case of immersion. To get the same strength, extraction, and beverage mass you need to up dose and only slightly increase the water amount. You can do the math or just adjust the ratio by 2. It's going to be a ballpark sort of thing no matter what because you can't nail the extraction. The theory of extraction is just an approximate model anyway. And the character of the extraction -- the ratio of extracted compounds -- is different even if the overall extraction is equal.