popeye wrote:Ok, thanks for explaining the colloidal suspension model. That helps me think about it in a new way. However, since TDS measurements at time 0 (And all times) were based off spent pucks (that were dried and re-brewed) doesn't my original question still stand?

Perhaps I am misunderstanding the description of Jim's experiment. But if I understand correctly...

Jim prepared six baskets of identical dose, grind, and tamp, and produced six extractions, stopping them dead in their tracks at varying times: after the first drop (time zero) and then at six-second intervals. The six variously spent pucks were collected and sliced into three layers, presumably equal to the eye, not by mass. At this point we have 18 slices.

These 18 slices were then oven-dried, as was enough coffee to make two more fresh espressos. After drying, the two fresh unspent doses were brewed at different dose-to-water ratios. The eighteen slices were also used to make more espresso, at another ratio, but all of them at the same ratio.

NOTE: I do not understand Jim's nomenclature for expressing these ratios. A ristretto is about 1:1 in dose-to-beverage weight and normale 1:2 and lungo 1:3, per Andy's scheme. Jim, are you going by volume?

The TDS of each of these subsequent extractions was noted. These 18 rebrews were then taste-compared by Jim against the two fresh cups made from the oven-dried 100% unspent fresh coffee.

In light of my (mis?) understanding of the protocol, I am not sure what you are referring to by "TDS for all three segments".

popeye asked:

The TDS for all three segments at time zero (roughly) averages to the TDS for the coffee. Shouldn't this be expected, because all the coffee - minus one drop - is still in the filter basket? In fact, it seems to be a good reality check for the measurements. So is the bottom absorbing the top, or is the dissolved top just in the process of flowing through the bottom? Sorry if i missed something in the description.

Regards
Timo

timo888 wrote:Jim prepared six baskets of identical dose, grind, and tamp, and produced six extractions, stopping them dead in their tracks at varying times: after the first drop (time zero) and then at six-second intervals. The six variously spent pucks were collected and sliced into three layers, presumably equal to the eye, not by mass. At this point we have 18 slices. ... These 18 slices were then oven-dried,

Yes

as was enough coffee to make two more fresh espressos. After drying, the two fresh unspent doses were brewed at different dose-to-water ratios. The eighteen slices were also used to make more espresso, at another ratio, but all of them at the same ratio.

No.

The oven dried puck-parts were brewed like regular coffee: 4 grams to 80 grams of water; I tasted the brew for strength (against the regular coffee brewed at 4, 2 and 1 gram per 80 grams) and measured the TDS. The more the puck part tastes like coffee, the higher the TDS, the less extracted it is.

another_jim wrote:The oven dried puck-parts were brewed like regular coffee: 4 grams to 80 grams of water; I tasted the brew for strength (against the regular coffee brewed at 4, 2 and 1 gram per 80 grams) and measured the TDS. The more the puck part tastes like coffee, the higher the TDS, the less extracted it is.

OK. I'm still a little confused about what happened after the oven-drying.

We have 18 oven-dried slices:

..................T0......T1......T2......T3......T4......T5
Top Layer.....1.......4.......7........10.......13......16
Mid Layer.....2.......5........8........11......14......17
Bot Layer.....3.......6........9........12.......15.....18

The puck from the cup where the extraction was stopped at the first drop is the T0 puck. The puck from the cup where the extraction was allowed to run to 30 seconds is the T5 puck. Each cup's puck was divided into three layers.

So far, I am clear.

When you made the regular brew from these slices after they were oven-dried, did you make 18 cups of regular coffee, with 4g being the actual oven-dried dose added to 80g of water, and then take 18 actual TDS readings?

Regards
Timo

timo888 wrote:When you made the regular brew from these slices after they were oven-dried, did you make 18 cups of regular coffee, with 4g being the actual oven-dried dose added to 80g of water, and then take 18 actual TDS readings?

Yep, those are the TDS readings I report (except I did two series of shots, so there's a pair of lines for each puck section). The horizontal lines come from 4 readings each of oven dried fresh coffee at 4, 2 and 1 gram per 80 grams. The water used was distilled, and had a TDS of around 6. TDS readings are not linear as you can see from the 3 concentration levels of the same coffee; but the three solutions of the unbrewed coffee give a scale for the puck concentrations.

There are two series because the same experiment was run twice?

One thing remains. The colored lines on the graph represent the TDS of the top, middle, and bottom slices of pucks T0, T1, T2, T3, T4, and T5, brewed as regular coffee in a 4g to 80g concentration. The y-axis represents TDS and the x-axis represent the six different pucks in the experiment. But there are seven items represented on the x-axis.

Regards
Timo

timo888 wrote:There are two series because the same experiment was run twice?

But there are seven items represented on the x-axis.

I was too lazy to set the X axis ticks at 6 second intervals, so they are at five. But the line segments run 0 to 6 to 12 to 18 etc. The segments connect the lower readings of each pair and the higher readings.

another_jim wrote:I was too lazy to set the X axis ticks at 6 second intervals, so they are at five. But the line segments run 0 to 6 to 12 to 18 etc.

You will have to change that for the hardcover edition

another_jim wrote:The segments connect the lower readings of each pair and the higher readings.

So the lines connect readings from different pucks belonging to the same extraction-time cohort? The data series were intermingled within cohorts for the graph?

Could you post the raw TDS readings for all 36 slices?

Did you weigh each oven-dried dose after the oven-drying, before brewing the 4g to 80g ratio samples? The 4g is an actual measurement and not an extrapolation from an initial 12g dose?

Regards
Timo