Refractometer 411

http://www.ebay.com/itm/Brix-Refrac...-CNC-Brew-ATC-Twist-Calibration-/190897534780
That one looks like the kind I got, the only difference is mine only outputs brix not SG but brix is the only one you should pay attention to anyway. Its good for a couple reasons that you should look for when getting yours. Easy calibration knob, and auto temperature compensation (ATC). Oh, and 0-32 should be all you'll ever need, some go up to 40 but thats really high gravity.
Looks like the same or similar seller too, I got mine on Ebay.

I think I may get a new one after about 6 years of use, mine seems to be a bit damaged. I've been pretty rough with it over the years and I was always impressed by its durability, but last time I used mine looks like maybe the inside lens cracked or is dirty or something. It didn't obscure the reading and it output right on my predicted OG so I think it still works but I may just replace it.

 

I'll just say I find the spreadsheets that do FG highly suspect. Their readings are generally nowhere near the ones I get from my hydrometer. Hydrometers have their place.

 

http://onebeer.net/refractometer.shtml
This calculator gives me accurate results. Every time I've checked with hydrometer or vibrating u densitometer its been spot on. For OG and FG.

 

Bought it, love it...that said I still use a hydrometer in conjunction:

http://www.amazon.com/Refractometer...&qid=1399345985&sr=8-1&keywords=refractometer

Bought the RF15 because it's made by ExTech...and not a generic knock-off:

http://www.extech.com/instruments/product.asp?catid=17&prodid=226

 

I can't stress enough how easy and nice the easy calibration knob is to use.

 

I will second this. I bought this exact one and I really like it. Only used it on maybe 3 or 4 batches so far but I really like it.

 

This is the site you are looking for. Sean Terrill has done his homework (research). He also had a recent article in Zymurgy, I believe. For low to moderate gravity beers his pre and post fermentation models are excellent at matching hydrometer readings. For a while I measured both just to check; I only use the refractometer now. For big beers the post fermentation model does not work very well, and so I would not trust it with a barley wine, for example. Details can be found on his website.

 

I found a formula a few years ago that uses coefficients with 6 decimal places, second and third powers on the BRIX numbers (pre and post fermentation), etc. I plugged these into a spreadsheet and the numbers I got were always within .002 of the hydrometer values (I verified all of the refractometer readings for my next six batches or so because, as everybody knows, a refractometer is not accurate. Once it became clear that 'everybody' was wrong, I retired my fourth and last hydrometer ). Unfortunately, I lost that hard drive and had no backup. Fortunately, I had printed a chart that I inserted in my notebook, so I can look it up easily.

Lamenting the fact that a refractometer is less accurate with high gravity beers is kind of silly when one considers that specific gravity (the number that the hydrometer gives us) is a poor indicator of sugar content, particularly post-fermentation, and particularly with high gravity beers (surprise!). It's true that alcohol affects the refractivity of the beer, but it also affects the density. We infer the sugar content from the final gravity, without factoring in the original gravity (a 1.010 beer that started at 1.050 has more residual sugar than a 1.010 beer that started at 1.100, for example, but we pretend it's the same). But we're all comfortable with these numbers and we can make predictions based on them, so we use them without giving it a second thought.

Curiously, the formula that I use to convert BRIX to SG accurately replicates the known inaccuracies of the SG as an indicator of residual sugar. But I'm comfortable with these numbers and I can make predictions based on them, so I use them without giving it a second thought .

Ideally, I would limit myself to BRIX (better yet, Plato) and do it correctly - or at least closer emulation of correctly. But the conversation among my circle of brewers is SG-centric, so I stick with that.

 

I decided to stop messing with cheap ones and bought this one. I like it and it is durable.
http://www.amazon.com/gp/product/B004WDRJUU/ref=wms_ohs_product?ie=UTF8&psc=1

 

I know what I'm about to say doesnt help... but Hydrometer all the way man! I broke one refractometer and wrote them off after that.

 

I use both. My refractometer has been consistently reading off on OG pre boil. The whole ATC thing just don't work. I would get like 74% Extract Efficiency when read with the refractometer after the sparge (and yes I mixed the kettle well), and then cool a sample in the fridge and get 86% with the hydrometer. I decided to chill the sample this past weekend before reading it with the refractometer and the numbers were much better (88%).

 

I use the refract and get my readings while mashing, sparging, and I'll take readings from the kettle pre and post, and use a calculator to figure out what I've got.

I also use a hydrometer pre and post as well to make sure everything was reading correctly. I'm usually within 0.002 between the two. Good enough for who it's for..

Mines hard as hell to read, as it's the ATC version that does brix/SG on it. I get damn near cross eyed looking into it sometimes after a few beers.

ATC doesn't do shit though, so I find better values when I pull my sample put it on the glass and let it sit for a couple minutes before getting my reading.

 

Since people are discussing ATC here I thought I'd chime in again.

I take a measured shot glass and grab a sample that's about two pipettes worth of fluid. Throw that sample in the freezer, and swirl it every 2min or so. It gets down to between 60-70° in about 5-6 min. That way I don't have to rely on the ATC...never really trusted it from the beginning.

Anyway, this method has kept my readings between the refract and hydrometer very close.

 

As utahbeerdude said, Sean Terrill's calculator is the one you want. FWIW, his model is also incorporated (with a couple twists) into BrewCipher.

 

I say the same thing too, but aren't you reversed? 1.100 has more alcohol (less dense than water) at 1.010, so it needs more sugar to get to 1.010?

 

I wouldn't say we necessarily pretend it's the same. The more accurate ABV formulae out there (the ones with more factors) adjust for this. e.g. the simple formula will give the same ABV for OG 1.100 to FG 1.050 as it does for OG 1.075 to FG 1.025. Not so for the improved formulae.

 

Your description is consistent with the Sean Terrill formulas for conversion from Brix to OG.

 

The ATC is for compensation of the ambient temperature (i.e., temperature of the instrument), not the wort temperature. Indeed a drop of wort will cool very quickly.

In some online videos I have observed homebrewers taking a spoon and pouring a generous amount of hot wort over the prism of the refractometer. This is a bad idea as this could appreciably change the temperature of the prism. Also, this could potentially crack the prism due to differential thermal expansion.