Refractometer 411

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Sorry for the serial posts, but one more thing. For those not on a budget, I highly recommend the Vee Gee BTX-1 refractometer. I bought it because it was touted to be easy to read. Indeed, this is the truth.

Edit: Amazon currently has a decent price.

 

A feature of Sean's formula (or any reasonable refractometer formula) is a Wort Correction Factor (WCF). Sean recommends a default value of 1.04, but suggests changing it if you're expecting attenuability significantly higher or lower than the batches in his test data. (Though he doesn't say how to derive the substitute factor, other than maybe by collecting lots of data and backing into it. Don't hold me to those exact words, but that's the gist.)

But...since BrewCipher actually does predict attenuation, I leveraged that fact to compute a recipe specific recommended WCF for use in his formula.

From the popup comments in BrewCipher...

"This is the recommended Wort Correction Factor. It will be used if nothing is entered for Override Wort Correction Factor.

This (recommended) Wort Correction Factor (WCF) is computed using the expected attenuabilty from the recipe. The formula that calculates this recommended WCF was derived by VikeMan, using two pieces of data... First, Sean Terrill's work, which found that a WCF of 1.04 is a good center for worts with an average ADF of 81%. Second, that a pure sucrose solution would require no WCF, i.e. a factor of 1.0.

WCF accounts for the fact that sugars/dextrins other than sucrose have a different refractive index than sucrose. Therefore a refractometer's Brix reading must be adjusted if the wort contains sugars/dextrins other than sucrose. (And they all do.) The WCF is used to apply this adjustment.

This recommended WCF calculation is not necessarily endorsed by Sean, whose shadow I merely walk in.

If you are uncomfortable applying this WCF derived using expected attenuability, you can apply an override. Sean Terrill's recommended default (based on the worts he tested) is 1.04."

 

You could be right. The point is, though, that, in order to get a reasonably good approximation of sugar content (the important number), you need to factor in OG. Vikeman's comment notwithstanding, we tend to use FG as if it's meaningful by itself.

 

I guess I'm out of touch. I wasn't aware of this. Looks like I need to do a bit more reading.

 

I pour a bit of distilled water on the lens, then wipe off with paper towel.

 

I soak up the beer with a paper towel. Then wipe very gently with a wet paper towel. Then soak up the water with a dry paper towel and allow whatever is left to air dry. Takes about 10 seoconds.

 

I give it a quick rinse under running water and let it air dry.

 

Keep an eye on http://www.homebrewfinds.com/ its a great place to find deals in the homebrewing world!

 

I actually do that.. Wipe it off on my shirt, or with my finger. I'll dunk it in my bucket of starsan to rinse it and toss it on the table.

 

There's really no need to sanitize it. The pipette, definitely, but not the refractometer.
...unless, of course, you dip it directly into the wort, post-boil.

 

Oh I know that. I'm not sanitizing it at all.. There's just a bucket of starsan there, and it cleans the crap off the lense easy enough and within reach. Just getting the sticky wort off the lens.

 

StarSan is not a cleaner, though it will clean that sticky bit of wort off the lens just fine. But you really don't want to put organic material in your bucket of StarSan.

 

Again, I know it's not a cleaner, but it's just easier when I'm out on the patio brewing to dunk it in there to get wet to wash the stuff off. As for getting stuff in the starsan bucket, ehh it's no big deal. I dump it out after every brew day just about anyways. I don't leave it around for days on end. I have a bucket I mix in the garage that I have sealed and used distilled water in that I keep around for small things like airlocks and things I use to do hydro readings and samples.

Point is, I just use whatever wet I can get to wash the shit off of it, and I have never deliberately "cleaned" my refractometer. Just get the beer off and put it away.

 

I do the same exact thing, StarSan then wipe it off on your shirt and forget about. I usually do 2.5 gallons of StarSan so I don't think the .0001% of "organic matter" will make any difference. It amazes me how anal some people are on brew days. My motto is clean as best you can and don't F it up (over think the process).

 

i have taken to using a refractometer for everything, including FG readings. I use BeerAlchemy for my brewing app, and the corrections for FG seem to be a little dubious (although the pre-fermentation corrections seem to be spot on). I found my corrected hydrometer readings were 4-5 points higher than my refract. Interestingly, for my latest batch, Sean's calculator matched up within 2 points of my estimated manual corrections.

 

I got a digital refractometer for Christmas and it's great. No more having to figure out where to read the blurry line on an analog one.