Also, before I get shoot, here's my method for measuring TDS.

Measured boiled water and coffee(post grind) with.0.1g scale.
Check the temp with calibrated thermometer (boiling water)
Brew the coffee (depends on whether it's French Press or Vac Pot)
Post filtration, give the solution a shake before taking out sample
Sample is filtered by 45um syringe
Measure dried tube weight (with miligram scale 0.1mg resolution)
Put the sample into tube and measured.
Dry the sample in tube with air & heat (95C)
Make sure the sample is completely dried by further drying (to ensure no reduction in weight after the extra steps)
Calculate TDS using excel (dried coffee residue/original coffee liquid weight*100% = TDS)

samuellaw178 wrote:Hi Mark,

With all due respect, I did. TDS, measured. It's in the post before.

I've also mentioned retention is lesser than 2g/g for siphon. It's in the text you quoted.

The 'picking up TDS' part is interesting. I would love to discuss that, but let's get the context/ambient straight first.



The variables are not new to me, which I have also implied in my posts. I know extraction yield is driven by grind,steep time,temp,brew ratio,agitation - all which are posted in my previous posts. And again, as I mentioned, I drink espresso mostly, I can't tell for sure my brew is weak or not - because naturally it's weaker than the espresso strength I am used to. That's the reason for the whole measurement exercise, so that I know which direction I have to move the extraction (because my palate is calibrated for espresso).

I know you may have not meant the tone you'd come across. To me, it sounded quite offensive because you had made yourself sounded like the absolute authority with a derogative tone and as if I know nothing (but all the information I had already posted if you do read).

My suggestion for a more productive discussion(not ended with the thread locked), it will help if you read your message before you post it, also it will also help immensely that you have read CAREFULLY what was posted before. Because, simply, I believe most of the people here are putting their great effort and forming their thoughts carefully before they let it out, so that HB stays as a place for high quality discussion. I know I do. That's also the reason I love and have stayed here at HB for so long even if I don't post (unless I've got something significant/important to share).

And your tips/guides posted are noted. Thanks, I do appreciate them.

Apologies, you did mention these factors, I missed it. I don't mean to appear "offensive", trouble is, for the pertinent information (brew water, beverage weight dose weight & %TDS), it's best if we can see it quickly & clearly...I appreciate there are a lot of thoughts flying around & a lot you want to say. As with many posters here, I guess we (I, in this case) don't always have enough time to fully dissect & disseminate & give as much time as it deserves...so again apologies, I don't mean to appear curt, or condescending, just time is an issue.

If you want your extraction yield measurements to have any kind of parity with the CBI method, weight the brew water at tap temp. Presumably your coffee beverage sample is allowed to cool to room temp & weighed before dehydration?

Peppersass wrote:The dilution doesn't change the extraction yield. What's happening is that only 460g of water is being used for brewing, not 560g.

Actually, referring to the tables in the OP's earlier post, 560g of water are used for brewing-i.e., in direct contact with the grounds-while an additional 100g of water remains behind in the globe. These variables (brew water vs. water in globe) are listed separately at the top of the two tables.

samuellaw178 wrote:Also, before I get shoot, here's my method for measuring TDS.

...give the solution a shake before taking out sample
Sample is filtered by 45um syringe
Measure dried tube weight (with miligram scale 0.1mg resolution)
Put the sample into tube and measured.
Dry the sample in tube with air & heat (95C)
Make sure the sample is completely dried by further drying (to ensure no reduction in weight after the extra steps)
Calculate TDS using excel (dried coffee residue/original coffee liquid weight*100% = TDS)

This is a side question, but I'm curious about your method, specifically the choice of temperature for drying. How large a sample and how long does it take with that nice piece of equipment?

Also, have you verified that your method is consistent and had any way to check accuracy?

Eastsideloco wrote:Actually, referring to the tables in the OP's earlier post, 560g of water are used for brewing-i.e., in direct contact with the grounds-while an additional 100g of water remains behind in the globe. These variables (brew water vs. water in globe) are listed separately at the top of the two tables.

I don't believe that's correct. Here's what the OP said:

samuellaw178 wrote:A quick calculation : 560g total water, 70g water retention in ground(Usual assumption of twice the ground mass, for vac pot it's lower), 100g water retention at bottom globe.

He provides a calculation of resulting beverage thusly: "560-100-70", which is starting water less the water retained in the lower globe, less the water retained in the grounds. That means 460g of water comes into contact with the grounds. The chart confirms this by showing that with retention of 70g of water in the grounds, 390g of brewed coffee flows back down into the lower globe. Add the water retained by the grounds, and you get 460g of water flowing up into the upper chamber and 100g staying in the lower globe. The total is 560g, but only 460g is used for brewing.

The VST software roughly confirms these brew parameters, though it comes up with 75g of water retained in the grounds instead of the OP's caclulation of 70g (i.e., 385g of coffee flowing back down to mix with the 100g of water left in the lower globe.)

MWJB wrote:If you want your extraction yield measurements to have any kind of parity with the CBI method, weight the brew water at tap temp. Presumably your coffee beverage sample is allowed to cool to room temp & weighed before dehydration?

Mark, all is good.

There is a reason I do that. Taking boiling water's weight prevents unintended evaporation effect. Water density changes as temperature does. 500g room temp water is 500ml and become 550ml(just for argument sake) when boiled. Cooling them down will just get them back to 500ml. Weight stays the same throughout regardless of temp(assuming no excessive evaporation). I can do that (measure tap temp), but I just *think* this is more logical/accurate because I don't have the same operating condition as when the CBI conducted the tests.

For sampling, I used weight not volume because volume is not accurate and weight will be less temperature-dependent. But yes, it was cooled to room temp by the time I'm drying it.

jpender wrote:This is a side question, but I'm curious about your method, specifically the choice of temperature for drying. How large a sample and how long does it take with that nice piece of equipment?

Also, have you verified that your method is consistent and had any way to check accuracy?

That's totally valid here. That's the highest temperature reasonably before it may char or change the dissolved solid in the coffee (since 90-95C is the brew temp). Also, I did some research here before on HB, and I think I see a reference to using that temperature. I would like to get even hotter for faster drying, but am afraid it will have unintended effect.

Sample size is 5g(thereabout). It depends on the accuracy & resolution of the scale. The more sensitive it is, the less sample you can get by. I thought of using my own 0.1g scale, but the resolution is insufficient and I have to use at least 100g sample for that. The miligram scale is able to resolve 0.1mg, and can do so with confidence in +-1mg. So I want my dried coffee weight to be at least 10 times more than that to be measuring something significant. The dried coffee ended up in the range of 60-70mg, which is good enough to get me in the range of fairly good estimate.

It took me about 2 hours total for drying and to confirm it's dried. It's in a tube so takes longer to dry.

I have verified it through taking duplicate sample (twice). Both trials seems to be very very close (1.435% vs 1.427%, and another one I need to check back my notes if that's important).

Accuracy wise, I would think dry and weight method is the gold standard for getting proper TDS (no brix meter or refractometer etc), before VST refractometer takes over. VST is essentially a more sensitive/accurate refractometer that takes refraction information. And that refraction data is correlated to the established dry-and-weigh TDS so that users don't have to go through the drying process every time.

Eastsideloco wrote:Actually, referring to the tables in the OP's earlier post, 560g of water are used for brewing-i.e., in direct contact with the grounds-while an additional 100g of water remains behind in the globe. These variables (brew water vs. water in globe) are listed separately at the top of the two tables.

My bad if it's not clearly presented. My definition of brew water is the total water that I've used for making the Vac Pot, which includes the lower globe retention.

Peppersass wrote:An interesting experiment would be to increase the dose to 41.5g, keeping the brew water and grind the same. That should give you an extraction yield of 20% and TDS of 1.70% -- before the coffee is diluted.

Thanks so much for your comments. You're spot on with the muted bitterness. That's what my dumb palate tasted but doesn't know how to describe.

As for the coffee dosage, if I bump that up with the others held constant, I would expect to see a bit more than 1.7% in the undiluted, and >1.43% in the final cup with extraction yield closer to 20%. Should be a stronger cup but less the bitterness. But from practical point of view, I think I will coarsen the grind size first, then reduce the steeping time, to achieve lower undiluted TDS (will aim for 1.5% range), that gets me closer to 20% yield.

Just curious, did the VST software come up with the 1.7% (for 41.5g dosage calculation) or it was a user-input value?

It's funny, I normally weigh and measure everything, but with the siphon I relax and just use the included scoop for the coffee and brew it in my Yama 8 with the water held in the top for a minute and it comes out great.

I know right, but you're on HB. Fussing with all these is not neccesary, really. I'm going to do a bit more and be done with it, but they're good mostly for my curiosity sake and to see if I can improve the taste a little.

samuellaw178 wrote:My bad if it's not clearly presented. My definition of brew water is the total water that I've used for making the Vac Pot, which includes the lower globe retention.

Gotcha. My bad for misreading. That definition makes the most sense.

Peppersass wrote:He provides a calculation of resulting beverage thusly: "560-100-70", which is starting water less the water retained in the lower globe, less the water retained in the grounds. That means 460g of water comes into contact with the grounds. The chart confirms this by showing that with retention of 70g of water in the grounds, 390g of brewed coffee flows back down into the lower globe. Add the water retained by the grounds, and you get 460g of water flowing up into the upper chamber and 100g staying in the lower globe. The total is 560g, but only 460g is used for brewing.

The VST software roughly confirms these brew parameters, though it comes up with 75g of water retained in the grounds instead of the OP's caclulation of 70g (i.e., 385g of coffee flowing back down to mix with the 100g of water left in the lower globe.)

I'm following now. Thanks for the breakdown.

I have two regrets about the brewing class that I took in last November: 1.) the coffee lab's siphon brewer was out on loan for a film shoot (random); 2.) the VST was out on loan (probably to one of the roaster's commercial accounts). As a result, I only got to take notes on the trainers preferred siphon recipe. And I have zero experience with the VST. Sounds like the VST hardware and software could be an 8-hour class on its own.