samuellaw178 wrote:May be the sludge is contributing to the increased 'perceived strength' on the Espro Press. My TDS reading for Press is 1.2-1.25% so the 'heaviness' definitely does not come from strength (alone)

TDS contributes very little to mouthfeel & the tactile perception of strength/body, with any press pot you pour out the coffee with oils & other particulates suspended in the brew, you can feel them but they're not dissolved & not counted towards TDS. In a vac pot, the oils are suspended in the immersion phase but significantly filtered out by the bed of sunken grinds (as well as any other filtration) in the top chamber, during drawdown, so the mouthfeel is usually lighter even when the %TDS is higher.

samuellaw178 wrote:4 minute includes the drawdrown. What grind size do you use for that 45 sec steep time? I reckon I could do drip grind too, just by adjusting the steep time. Another thing to do.

I play with different settings within the Electric Perk to Drip range on Bunnzilla. Currently I'm grinding just a little coarser then drip.

What filter are you using? Cloth? Paper? Stainless mesh? The stainless mesh will get you closer to a Press Pot brew mainly because you'll end up with sludge in the pot & cup. I use the cloth filters which keep out the sludge but do allow the oils through unlike the paper filters.

MWJB wrote:TDS contributes very little to mouthfeel & the tactile perception of strength/body

This is a new revelation to me, I'm glad I started the thread.

JohnB. wrote:What filter are you using?

The Vac Pot is a Cona Size D. I'm using the glass rod filter that came with the Cona D. Works quite well actually considering how simple the construction is. One interesting observation - I get less sludge on the finer grind, than with a coarse grind. But I'm not trying to replicate French Press on the Vac Pot. Cloth filter is something I would love to try one day, but it seems to need a little more attention in maintenance than the others.

Did you weigh the beverage, as I suggested?

Yup..that's how I get the water evaporation and ground/water retention.

For the 3 minute steep, these are what I get:
Coffee : 35g
Brew Water : 560 g
Final Brew weight: 495 g

Vac Pot Top globe immediately post brew : 410.5g
Vac Pot Top globe weight (cleaned & dried) : 324.2g
Water Retention+coffee ground(35g) = 410.5-324.2-35 = 51.3

495+51.3 = 546g (14g evaporated)

For this brew, final tds was 1.365%.

Edited my previous post where I had stated my drawdown time was in the 2:25 range. That is actually the total contact time which includes steep time & drawdown. Shouldn't post before the morning coffee has taken effect!

This thread made me start using my Yama stovetop siphon pot for daily brewing... and order a new Hario TCA-5. At least I resisted the halogen heater for now



After a bunch of trial and error, I'm using a 600:41 brew ratio aiming for 1.3% TDS and 20% extraction with timing identical to John's. With the water in the upper chamber at the appropriate temperature, I dump in the grinds, give it a good stir with an Aeropress paddle, wait 45 seconds, give it a second stir with some spin, and aim for a sub-1:30 drawdown. I get the final brew weight by weighing the entire pot and making appropriate subtractions. I get the diluted beverage weight by weighing the carafe and subtracting its weight. My water loss ratio is indeed about 1.5 g/g dry weight coffee, which in VST parlance is more like 1.8.

My Yama pot retains about 60 g of water in the bottom chamber, based on the averages of a few tests. This is only 10% of the brew weight and gives an inconsequential 0.3% extraction calculation error at the strength I prefer. If I were brewing one cup, the error would double, so I will keep it in mind and measure the Hario pot as well.

It was enlightening seeing how easily you can overextract a siphon pot brew. I was originally using more typical two minute brew times and having to grind really coarsely to get anything drinkable. With the 45 second brew I get very consistent results using the same grind I use for two cup V60 brews. These are by far the best results I've ever obtained with a siphon pot.

I'm interested in the dynamics of what's happening in the top chamber during the drawdown. As Mark mentioned, there is sometimes a significant TDS difference between the slurry and filtered coffee after compensating for dilution. I haven't really made enough measurements or found any consistencies yet, and it's often negligible.

Bob_McBob wrote:I'm interested in the dynamics of what's happening in the top chamber during the drawdown. As Mark mentioned, there is sometimes a significant TDS difference between the slurry and filtered coffee after compensating for dilution. I haven't really made enough measurements or found any consistencies yet, and it's often negligible.

It's got to be ~11% increase on top of slurry concentration in top chamber & before hitting the retained brew water in the lower chamber.

Bob_McBob wrote:It was enlightening seeing how easily you can overextract a siphon pot brew....

....I'm interested in the dynamics of what's happening in the top chamber during the drawdown. As Mark mentioned, there is sometimes a significant TDS difference between the slurry and filtered coffee after compensating for dilution....

Exactly! I am really surprised that my brew overextracted by that much, using fairly similar parameter for other method. The drawdown must have something to do with it. It's probably similar to espresso process? Forcing the coffee liquid through the coffee bed formed, bringing more dissolved solids as they go down. The drawdown is probably not just a filtration process as we thought it to be.

MWJB wrote:It's got to be ~11% increase on top of slurry concentration in top chamber & before hitting the retained brew water in the lower chamber.

Mark, you seem to already have a grasp on what's going on. Sorta like 'been there done that' for you. Have you figured out what's happening there?

samuellaw178 wrote:Yup..that's how I get the water evaporation and ground/water retention.

For the 3 minute steep, these are what I get:
Coffee : 35g
Brew Water : 560 g
Final Brew weight: 495 g

Vac Pot Top globe immediately post brew : 410.5g
Vac Pot Top globe weight (cleaned & dried) : 324.2g
Water Retention+coffee ground(35g) = 410.5-324.2-35 = 51.3

495+51.3 = 546g (14g evaporated)

For this brew, final tds was 1.365%.

OK. So, let's compute the %TDS prior to dilution using this formula:

(Final %TDS x Final Weight of combined Beverage) / Initial Weight of Beverage

Assuming the water retained in the lower globe is 100g, the Initial Weight of Beverage (i.e., pre-dilution beverage weight) is 395g. That gives us a pre-dilution TDS of 1.71%.

Using inputs of 35g of coffee, 395g of beverage and TDS of 1.71%, the VST software to computes the extraction yield to be 24.28%. More over-extracted than you thought.

While the strength of the diluted beverage is right where you want it, the cup will probably have that muted bitterness we talked about before.

If you updose to 44.7g and increase the total water to 590g (includes 100g retained in the lower globe) and adjust the grind so that your draw down time remains the same, and use the same 3 minute steep time, you should get an extraction yield of 20.02%. I calculated that using the same 1.71% TDS and 395g of pre-dilution beverage so that you'll get about 1.35% TDS after dilution.

With both extraction yield and %TDS in the middle of the range, the cup should be well balanced and of medium strength. It would be really cool if you could try this recipe.

Note that the VST software computes the Brew Water weight to be 470g, which is pretty close to the actual 460g, but not exactly the same. It also computes the weight of the spent grounds to be 108g, so the retained water is 73g. Subtracting 14g for evaporation would give us 59g, which is pretty close to your 53g. Not sure why the numbers don't match exactly. Could be some error in your TDS measurement or perhaps the default parameters used by the VST software for CO2 and moisture figure into the discrepancy.