Well I have been considering one for a while and have just pulled the trigger. Let's see how it plays:)

Woohoo! Way to jump in;

Welcome to a new "day"! This thread has got your back! Because you are the first to come to the dark side I will do everything I can to help the you get there. Where?

Being able to define your God-shot via refractometry and hitting it consistently.

SUPER MEGA BYE BYE GOD-SHOT SECRET: The dark side no longer has mysterious, random God-shots! Waaahaaahaaa:/ Once you can define your God-shot via refractometry and hit it consistently; the term is no longer necessary and productive other than to define an ideal personal recipe for a coffee bean and age on your gear with your refractometer. I'm sorry for taunting the god shots btw; they taunted me first;/

The focus returns to bringing out the best in the fruit, defining your god shot (dose, brew ratio (beverage:dose), EY% and TDS%), repeating it consistently and letting the technique and equipment disappear and become habit;) Bye bye God-shot and good riddens

Apogee wrote:<image>THE SECRET REFRACTOMETRY FORMULAS!!!

So you don't have to buy the $50 VST coffee tools pro for iOS EY% app (which I love and highly recommend). Simple calculator will do. Save $50! However you calc it. Test it and then don't change it*

Secret Refractometry Formulas:

Espresso & Drip EY% = TDS * brewed coffee weight / ground coffee weight

Immersion EY% = TDS * brew water weight / ground coffee weight

TDS = Brix * .85 (at room temp)

Tom,

Before anyone goes crazy about it, I think it's worth highlighting that the actual Brix to TDS conversion isn't that straight forward. As it's been mentioned, the relationship of Brix and TDS is not linear. I recall that someone has done some work in the past and by using the 0.85 factor, you could get deviation as much as +/-0.16 TDS% (which could easily mean +/- 0.32% EY for a typical 1:2 brew ratio) - across the TDS range of 0-20%. For home use and for consistency checking purpose, that probably doesn't matter so much.

Apogee wrote:Being able to define your God-shot via refractometry and hitting it consistently.

What is God shot exactly??? I can't recall ever having a Godshot anymore in the past 2 years. Has my palate got numb from all the supposedly god shots? I do have a coffee refractometer and while I have good shots, but none of what I'd call a god shot.

With everything at room temperature; error drops far below impact of other factors. Tested over 200 shots against VST, and manual refractometer and filters; the refractometer model or sample technique just didn't matter (as long as both were at room temperature for the reading). There were slight differences in TDS and EY% but consistently slightly different and always having the same peaks and valleys to guide behavior.

However you need to get to EY% and TDS to feel accurate. I recommend going there, including spending $1000k on the VST refractometer, syringes, filters and case if this is what you need to silence the voices. I did. It's awesome. As always. Find the shortest path your comfortable to lock down accurate measurement. Test it and don't change it*

Apogee wrote:That document is incorrect. I bought the refractometer and filters from VST (who I love btw! Their baskets are worth an easy .5%) and tested both ways. Check out the testing done referencing the Atago refractometer if you need by Socratic I believe. Mostly though, stop reading web pages, buy a refractometer and test for yourself.

I've owned a VST refractometer since the Lab I was introduced. I currently own a VST Lab III. I've used VST refractometers and CoffeeTools for years on a wide variety of coffees, roast levels and brew methods.

The document is not incorrect. It uses a tighter definition of accuracy than yours. For purposes of calculating extraction yield, the accuracy required to measure the TDS of brewed coffee is far greater than the accuracy required to measure the TDS of espresso. You might get useful relative results (not necessarily absolute results) measuring espresso with a cheap Brix meter, but you won't get useful results for brewed coffee.

Can you provide us with your test results? Did you compare the measurements using brewed coffee?

I read the Socratic studies. First, the Atago Coffee-PAL isn't a cheap Brix meter. It uses technology similar to VST, though with less expensive components that aren't as accurate or repeatable. Your Brix meter isn't even close to these devices in terms of accuracy. It's designed for measuring sugar water. So you're comparing apples and oranges. Second, there were a number of flaws in the procedures Socratic used in the first study. They corrected some, but not all of the flaws in a subsequent study. Third, they never answered the question about who supplied the Atago refractometer (i.e., was it an off the shelf model or did Atago provide it knowing that it would be used for testing?) The studies are moot at this point, at least in the US, because the Atago Coffee-PAL is no longer available for purchase in the US. Do some Googling on Atago and VST patents, then draw your own conclusions about that.

My point is that it's fine to say that your cheap Brix meter is OK for relative measurements of espresso. I'd certainly agree with that. It'll tell you when your espresso is stronger or weaker, and you can use a rough conversion of the reading with VST CoffeeTools to determine if changes that you make increase or decrease the extraction yield. You can correlate various extraction yields with sour, bitter or balanced taste. But your extraction yield measurements won't compare with measurements made with accurate refractometers. It won't mean anything to say, "I got 20% extraction yield by doing thus-and-such." When Matt Perger and I say 20%, we're talking about the same extraction yield.

And since greater accuracy and repeatibility are required for brewed coffee, even relative measurements won't be reliable. Brewed coffee may not interest you, but it does interest others. So it's not right to make blanket statements about the accuracy of your Brix meter. You might mislead some readers into buying a piece of equipment that's not suitable.

As for filtering espresso and other unfiltered brew samples, you would need to test a wide variety of coffees and roasts to convince me that a constant factor can be used to adjust for the undissolved solids.

samuellaw178 wrote:What is God shot exactly??? I can't recall ever having a Godshot anymore in the past 2 years. Has my palate got numb from all the good shots? I do have a coffee refractometer and while I have good shots, but none of what I'd call a god shot.

What is your definition of a God shot via refractometry?

Bean
Drink type
TDS
EY%
Brew ratio
Time

I'm going to disagree with everything Peppersass says and move on.

I have tested side by side with differences less than .2% consistently. Same peaks and valleys; identical.

Refractometry is no longer expensive technology, the accuracy of the Milwaukee is far within the variances of other factors.

This is beginner's refractometry. I couldn't care less about comparing to Perger. I cared about defining my god-shot for any given coffee and hitting it at will.

Any perceived differences in refractometry did not impact my results. Money remains better spent on the coffee and grinder. Find the way you like to calc EY%. Test it and don't change it*

Peppersass wrote:When Matt Perger and I say 20%, we're talking about the same extraction yield.

Hopefully you are both using the default CO2 and moisture values in the VST app, or one of you might actually mean 19.3% or 20.7% relative to the other

samuellaw178 wrote:Before anyone goes crazy about it, I think it's worth highlighting that the actual Brix to TDS conversion isn't that straight forward. As it's been mentioned, the relationship of Brix and TDS is not linear. I recall that someone has done some work in the past and by using the 0.85 factor, you could get deviation as much as +/-0.16 TDS% (which could easily mean +/- 0.32% EY for a typical 1:2 brew ratio) - across the TDS range of 0-20%. For home use and for consistency checking purpose, that probably doesn't matter so much.