Measuring Brew Strength - Optical Refractometer - try it travel thread!

[BoldJava]

I read through the post and can't find a 2nd taker.  Is there one in the house?

My experience.  
1)  I think the refractometer needs distilled water for re-calibration.  My readings were off in comparison to the .85 x TDS.
2)  I have read too much on this, TDS vs Brix, trying to find an entry point.  I will stop here.

In all seriousness, I don't have the background to understand the food chemistry involved -- the TDS meter, let alone compare it to a refractormeter.  I gave it the old college try but came away merely confused.  Thread at http://www.coffeed.com/viewtopic.php?f=17&t=2489 has some good reading, it only I could latch onto it.

As kids, we actually played with mercury (before we knew the toxicity) and would keep it in a vial, adding to it whenever we dropped a glass thermometer. We used to push it around on a glass table, always trying to pick it up.  Impossible. Getting my mind around TDS and refraction has taken me back to "picking up mercury."

Who is next?

B|Java

[gt]

Just curious, what reading did you get on the refractometer (the value)?

[BoldJava]

Just curious, what reading did you get on the refractometer (the value)?

123 on TDS
120 on refractometer
---
118 on TDS
117? on refractomer (increments are tiny and my eyes are not good)

[John F]

123 on TDS
120 on refractometer
---
118 on TDS
117? on refractomer (increments are tiny and my eyes are not good)

Can you imagine if you got 142 and 109.... or even 117 and 117.   


  

[BoldJava]

Can you imagine if you got 142 and 109.... or even 117 and 117.  


 

Yes I can.  You must have been in my chemistry class.

[ecc]

I hope I haven't muddied the water too much already, but can't resist risking adding further mud to the mix with one more try...

Espresso it is easy to see when you are under or over extracting a shot, and it is easy to taste the consequences.  Not everyone agrees as to the perfect extraction ratio, but we can talk about ristrettos, overloading, letting shots go long, etc.  Adding water to it for an americano doesn't change the extraction rate, but does change the strength.  Extraction rate and strength are obviously different.

In brewed coffee things are much harder.  Without measuring everything, and then dehydrating the remaining grounds to get the final amount of mass that got extracted, (and hopefully went into the coffee) it is very hard to figure out how the extraction went.

The refractometer is just a way to back into this observation of the extraction, but we have to know the water:ratio to use the TDS shortcut since we measure the destination (in the cup) rather than the source.  (in the grounds) Although it doesn't read TDS directly, the refractometer may be a better path to TDS in terms of accuracy than the conductivity meter you have that reports TDS directly. I know the SCAA recommends conductivity meters for TDS, but it might be screwing you up more than helping.

[gt]

Was the 120 refractometer reading like the picture below with the blue/white intersection down at the red line?

If so the %TDS was .85 times 1.2 or 1.02% (on the weak side).

[ecc]

Thanks for the image GT!  The meter we have is inverse, the blue covers the lower part of the scale.  The example below would read 5.3 (the red line I think was added by GT to illustrate the reported reading)

The consistency of B|labPartners readings is pretty good.  I aim for readings in the 1.4 - 1.5 range on the refractometer, but I do like brewed coffee strong.  If my tastes didn't coincide with the Bunn chart, I'm sure I would change my palette (not!)

Just to make sure it wasn't knocked around too much in the mail, it  might be interesting to take a reading from tap water.  My city water tested really close to 0.0.  Again, testing to a certain value is interesting, but mainly I use it to compare brewing methods, grinder changes, trying to improve the crap office drip, etc.

[BoldJava]

...
Just to make sure it wasn't knocked around too much in the mail, it  might be interesting to take a reading from tap water.  My city water tested really close to 0.0....

I just ran this and tap water ran just a hair below 0.0.

[ecc]

Bump, last chance for the quantitatively curious!  Try it, maybe your coffee will like it!

[BoldJava]

Refractometer is headed back to Hoosierville.  No March madness this year, http://espn.go.com/mens-college-basketball/team/_/id/84/indiana-hoosiers.

B|Java

[ecc]

I guess the old optical refractometer and the table just don't have the appeal of the ExtractMojo setup. 
Maybe if I mount a slide rule on it...   

Us hoosiers hedge our bets, we still have Notre Dame, Purdue, and Butler in!