[ashcroc]

21.7 certainly sounds like ambient temperature. Try it outside to confirm your suspicions. It'll be a lot lower this time of year if it is.

 

[Scotford]

not sure you need to worry about measuring/recording the TDS of the water

I always take a water tds reading when refracting so you know what pitch in what country you are playing on. Differing tds counts will give you different extraction rates.

I keep my water at the shop to around 50ppm total tds at max specifically for this reason.

Evenness evenness evenness.

 

[Phobic]

That makes sense in a commercial environment where you're controlling the TDS of the water you use, in a home environment when using bottled water with a consistent TDS it's a bit over kill though

not sure how controllable/consistent TDS in plumbed in filters systems are in the home though.

 

[MWJB]

I always take a water tds reading when refracting so you know what pitch in what country you are playing on. Differing tds counts will give you different extraction rates.

I keep my water at the shop to around 50ppm total tds at max specifically for this reason.

Evenness evenness evenness.

50ppm is 0.005%TDS to put it in perspective.

If you're brewing with 500ppm water your coffee won't taste great whatever your extraction, assuming most folk are under 200ppm the TDS of the water isn't a significant issue.

You zero with distilled/DI water because it is known datum. Your coffee refractometer isn't the right tool for assessing TDS of your brew water.

 

[Scotford]

50ppm is 0.005%TDS to put it in perspective.

If you're brewing with 500ppm water your coffee won't taste great whatever your extraction, assuming most folk are under 200ppm the TDS of the water isn't a significant issue.

You zero with distilled/DI water because it is known datum. Your coffee refractometer isn't the right tool for assessing TDS of your brew water.

Not entirely the point I was making. More of reducing variables to a more manageable level.

50ppm total tds water with extract differently to one with a 125ppm tds giving two different EY% readings.

 

[MWJB]

Not entirely the point I was making. More of reducing variables to a more manageable level.

50ppm total tds water with extract differently to one with a 125ppm tds giving two different EY% readings.

Sure, but the effect of brew water TDS is more of an accuracy aspect (to a point that is overkill in terms of meaningful results) more than one of consistency, with similar TDS water brew to brew, same coffee, managing your variables should be keeping you to +/-0.5%EY, or less, for 2/3 of your brews.

 

[the_partisan]

Does anyone have experience in mixing a reference solution? I get the slight feeling that my readings are higher than it should be - since I'm tasting the coffee is somewhat underextracted at 1.35% TDS and 20.7% EY.

 

[Mrboots2u]

Does anyone have experience in mixing a reference solution? I get the slight feeling that my readings are higher than it should be - since I'm tasting the coffee is somewhat underextracted at 1.35% TDS and 20.7% EY.

Few points and questions

Are you following the vst protocol for measuring? And coffee tools

? Just coz it's 20 percent doesn't mean it will be tasty btw ...

What are you using for a reference solution .

What's your data for the brew ? Dose ? Bec weight etc ?

Lastly describe the taste as opposed to under and over extraction, how does it stack up v the tasting notes ?

 

[GlennV]

Does anyone have experience in mixing a reference solution?

Yes. Add 24.9g of pure cane sugar to 975.1g of distilled water (so 1000g of soln). This should read as 2.00 tds at around 20C.

 

[MWJB]

Does anyone have experience in mixing a reference solution? I get the slight feeling that my readings are higher than it should be - since I'm tasting the coffee is somewhat underextracted at 1.35% TDS and 20.7% EY.

If it is 20.7% it probably isn't under extracted with a conical burr grinder. However, if the extraction is uneven, there may be elements of under-extracted flavour at a nominal extraction. Are you stirring your pre-wet/bloom?

The coffee may play a part, if I have a natural/honey process that tastes great at 18.5% I don't beat myself up trying to nail 20%, likewise if a Kenyan tastes good around 21% I see no reason to reduce extraction, unless I get any lingering, unpleasant bitterness in the last sips.

I just brewed a cup at 20.6%EY that had under-extracted flavours too (unripe fruit, sherbet almost fizz on the tongue, background of dryness)...I suspect it was uneven.

 

[the_partisan]

If it is 20.7% it probably isn't under extracted with a conical burr grinder. However, if the extraction is uneven, there may be elements of under-extracted flavour at a nominal extraction. Are you stirring your pre-wet/bloom?

The coffee may play a part, if I have a natural/honey process that tastes great at 18.5% I don't beat myself up trying to nail 20%, likewise if a Kenyan tastes good around 21% I see no reason to reduce extraction, unless I get any lingering, unpleasant bitterness in the last sips.

I just brewed a cup at 20.6%EY that had under-extracted flavours too (unripe fruit, sherbet almost fizz on the tongue, background of dryness)...I suspect it was uneven.

You're probably right. Also I think my little electric grinder combined with a single pour doesn't always give the most consistent results. The drain time seems to depend on how fines are placed maybe? With same grind size I got a drain at 2:30 and one at 3:00, while the 3:00 one was perfectly sweet, the 2:30 had these underextracted notes. The 2:30 came at 20.7% and the 3:00 21.6%.

 

[the_partisan]

Did one more brew, though not same beans, but fairly similar. Using 1 coarser grind setting and 6 pours with 250g total and 20s between each pour, with the last pour coming at 2:10, this time it took _very_ long to drain at 4:50. The refractometer read was at 21.25% EY. Seems I would need to go coarser to hit my target of around 20%. I was quite surprised that it wasn't way overextracted since it took so long to drain. It could also be the very low mineral content water I'm experimenting with. It feels like with a fixed brew ratio, there is some limit to extraction yield.

 

[the_partisan]

For those who weight the brew water, what LRR do you get? Mine doesn't seem particularly consistent - so wondering why this is the case. For 15g/250g brews I get values that range from 2.4-2.7 and the final beverage weight can have a big impact on the final yield.

For example given: BW: 250g, Dose: 15g, TDS: 1.4

If beverage weight is 219g, this will give LRR of 2.33 and EY of 21.4%

If it was 214g, this will give LRR of 2.7 and EY of 20.9% - quite significant difference.

What causes low or high LLR? There is also quite significant evaporation happening during brewing.

 

[MWJB]

Evaporation during brewing isn't significant, it's only a couple of grams & doesn't affect the LLR or gm bev. If you've added 250g total every time, using the same method, that's consistent enough.

+/-0.25%EY isn't really what I'd call significant, less than 0.02%TDS.

Different coffees can hold different amounts of liquid at the end of brew, so can different drip brewers - flat bottomed & flat bottomed V cones hold back more than Chemex & V60. If you want to be absolutely consistent a second pair of scales on a drip stand, under the cup can see you nail gm bev to the gram every time, but personally I let all brews drip out (unless I'm being a bit nerdy) & just accept that some coffees will be different to others. For the same coffee & brewer+/-2g (1% brewed weight) might be typical without intervention, your brew water added will probably be +/-1g?

 

[the_partisan]

I saw on Scott Rao's blog that he mentioned using a settings of "0" for CO2 and H2O when calculating EY. This essentially means EY = Coffee Out * TDS / Coffee In for drip brews.

I noticed that calculating this way reduces the EY calculations compared to default settings in the VST app by 1%. I'm not sure which way is the right way to go?

 

[MWJB]

Stick to one or the other, don't mix them.

I use the VST defaults because we know roasted coffee still contains moisture & CO2.

 

[the_partisan]

Sure but it makes comparing numbers tricky. I asked him now and curious how he'll elaborate on it.

 

[MWJB]

Sure but it makes comparing numbers tricky. I asked him now and curious how he'll elaborate on it.

Not if you're comparing numbers between your own readings via a consistent convention, or, if people state whether they have allowed for non-coffee mass.

VST developed the coffee refractometer, to me it makes sense to follow their protocol. I think at some point fairly recently the moisture aspect was inadvertently overlooked in brewing manuals (one of Scott's books clearly states "dry coffee", which could be interpreted both ways). If your dose is 3% water, you won't know whether that water was brew water, or water held in the coffee when you dehydrate samples, CBI & MIT used Schwartzmann's 1953 method for determining moisture in roasted coffee, also AOAC have an official method for measuring moisture in roasted coffee.

 

[the_partisan]

I find that following this protocol really works for me, if I want to refract:

1. Brew (drip) coffee into a glass carafe

2. Stir

3. Tare the scale with an empty mug on top. I use the therma cup, since it keeps the coffee warm pretty long.

4. Decant into the mug and note the weight.

5. Use a pipette to draw some liquid in, I do this a few times since I reuse my pipettes. Put the pipette aside. The liquid in the pipette will not evaporate.

6. Taste / enjoy the coffee for a while, and then use the pipette to drop a few drops to the metal sides, not directly on the crystal. This will rapidly cool the sample down.

 

[Zephyp]

Can you make your own distilled water with a pan on a stove and ice cubes or does it need to be prosessed in some other way?