Thanks. It's good to get a full report of the workflow you use.

I found it particularly interesting how different waters affect the extraction. It makes sense why some cafes find it so useful when setting up their brew bars. For instance, Counterculture, who have training centers in several cities, use it for that purpose.

I don't own and haven't played with a VST refractometer* but ran across a call for data from David Walsh. If you have a VST and want to participate, you can find the form with links to a blog post to contribute to a data pool that will be shared and could produce some interesting results. The form can be found here.

*I've tried optical BRIX meters, triple-scale hydrometers, and electrical conductivity TDS meters

Do you need to use 1 filter for measure? So you have to spend $1 just for 1 measure?

Peppersass wrote:Also, as I mentioned, it's easy for the tongue to get overwhelmed by strong flavors during a dialing-in session, at which point it's easy to get confused about what I'm tasting and which direction to go. Taste memory is notoriously unreliable, at least for me, and it's easy to forget what something tasted like in the time it takes to prep the next shot. The refractometer provides an unbiased number that can help me cut through the taste confusion.

In this way, I suppose, it is not unlike a sound engineer using a sound pressure level meter.
Human hearing undergoes "threshold shift", where the perception of loud sound is distorted upon constant exposure such that it doesn't sound loud, but becomes the new normal. This leads to the inexperienced sound engineer making it a little louder, getting used to the new loud, then making it louder still, etc. Using a sound pressure level meter allows the engineer to objectively measure the sound intensity instead of relying on his senses which are feeding him shifted readings.

Other senses display this sort of shift - if you've been driving down the highway at 70MPH for a long period of time and get off on an exit ramp, your perception of speed is skewed and you might be going faster than you think.

Our senses are programmed to ignore, or mute, constant inputs. I don't see why taste wouldn't be subject to this as well.

Of course, mineral water and crackers are cheaper...

Viernes wrote:Do you need to use 1 filter for measure? So you have to spend $1 just for 1 measure?

Yes, you use one syringe filter for each espresso measurement. Actually, they cost $1.39 each if you buy the 100 pack. You don't need to use a syringe filter for coffee that's brewed using a paper filter (drip, vac-pot, etc.) VST sells two kinds of syringe filters, one for espresso and one for unfiltered coffee. The syringe filters for unfiltered coffee are $0.99 each in a 100 pack. I don't know what the difference is between the filters because I don't have any of the unfiltered kind (French Press is not my thing.)

The cost of disposables concerned me, too. But I've done some optimization and learned to live with it. The syringe filters are by far the most expensive disposable. I've scoured the web trying to find cheaper syringe filters with the same specs, but it turns out that VST's price is about as good as you can do for that hole size and filter diameter. Smaller diameter filters with the same hole size are somewhat cheaper in quantity, but I've not bought any to test them against the VST filters. The test would be relatively simple (compare the extraction percentage across a range of different coffees and extractions.) But it'll cost me some money to find out because these things are mostly sold in large quantities. I'd hate to buy 100 smaller diameter filters, only to find out that they aren't suitable.

There are three other disposable items: a plastic 5 ml or 6 ml syringe, a plastic 1 ml pipette, and a standard alcohol swab. The syringe is reusable many times, but eventually the markings wash off. Not critical, but that's when I throw them away. The 100 filter pack comes with 5 reusable syringes, and you can buy additional syringes from VST. I found a comparable 10 ml syringe by B&D for pennies apiece that can be reused even more times, though eventually the markings wash off of them, too. I bought 100 of them, so I won't need syringes for a long, long time. I also found a supply of identical 1 mm plastic pipettes that are very cheap as well, and bought 500. The alcohol swabs can be bought at CVS or any warehouse store quite cheaply, and probably much cheaper on the web.

The cost of the syringe filters is a secondary reason why I wouldn't use the refractometer to measure every shot (aside from it not being practical or useful.) I only use one or two syringe filters when dialing in a new coffee. By new, I mean a coffee I've not used before, not a new bag of a coffee I've pulled before. If I've pulled a coffee before, I won't measure the extraction yield again unless the coffee isn't pulling the way it did before.

I don't measure until I get the flow rate pretty close to what the recipe specifies. For example, if the roaster recommends a 19.5g dose producing 32g of beverage in 28 seconds at 200F, I'll use those parameters and adjust the grind until I hit close to 28 seconds. Then I'll measure the extraction yield and taste the coffee, adjusting the parameters until the extraction gets to the 18%-20% range and the coffee tastes well balanced. From there I may tweak the extraction to adjust the balance in a particular direction, and will usually measure it when I hit the taste I'm after. The %TDS and extraction yield become part of the recipe record I store in MojoToGo on the iPhone.

Late to the party on this.. I did a search for extractmojo before I created my thread, but most of the details I've been looking for were here under a different title.

I'm kinda turned off by the thought of expensive one time use only filters. That really puts me off the thought of wanting one. I thought sterile syringes would suffice to draw up and apply a droplet of coffee onto the sensor without skewing the results. If that's not the case, I think I might just pass. It's not a matter of palate training, but objective data is fun to have to contrast against subjective inputs.

Instead of filters, the coffee can be centrifuged and the supernatant used for the refractometer. EBay has numerous used centrifuges for <$100.

In addition to a centrifuge, get a calibrated pipette. Makes measurement that much easier.

TomC wrote:Late to the party on this.. I did a search for extractmojo before I created my thread, but most of the details I've been looking for were here under a different title.

I'm kinda turned off by the thought of expensive one time use only filters. That really puts me off the thought of wanting one. I thought sterile syringes would suffice to draw up and apply a droplet of coffee onto the sensor without skewing the results. If that's not the case, I think I might just pass. It's not a matter of palate training, but objective data is fun to have to contrast against subjective inputs.

No, you must use the filters for espresso. Is not about sterilization, is about to filter the coarser particles that have passed thorough the metal filter.

chang00 wrote:Instead of filters, the coffee can be centrifuged and the supernatant used for the refractometer. EBay has numerous used centrifuges for <$100.

In addition to a centrifuge, get a calibrated pipette. Makes measurement that much easier.

More information about this will be welcome.

The centrifuge separate the coarser particles? Anyone tried this instead the filters?

I knew it had nothing to do with being sterile or not. There's no way I'm adding a centrifuge and the time to spin down a sample in order to proceed. There's only so much geek in me.

I can get IV line filters as well which will do. But I still don't think I'll bother yet.

Peppersass wrote:The cost of disposables concerned me, too. But I've done some optimization and learned to live with it. The syringe filters are by far the most expensive disposable. I've scoured the web trying to find cheaper syringe filters with the same specs, but it turns out that VST's price is about as good as you can do for that hole size and filter diameter. Smaller diameter filters with the same hole size are somewhat cheaper in quantity, but I've not bought any to test them against the VST filters. The test would be relatively simple (compare the extraction percentage across a range of different coffees and extractions.) But it'll cost me some money to find out because these things are mostly sold in large quantities. I'd hate to buy 100 smaller diameter filters, only to find out that they aren't suitable.

You could try to pass a few ml through a regular drip filter and compare that to your original syringe filter. After doing it a few times, you'll probably find that either the readings are very similar, or you will find that there is a constant delta between the two. In any case, if the reading difference are consistent, you will know how to compensate the reading on the VST.

After all, the coffee refractometer relies on the filter of the drip coffee to do the filtering. Why not for the espresso too than.