Refractometer

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Refractometer

Postby Bowhunter » Mon Jan 20, 2003 6:54 am

I am interested in purchasing a refractometer and would like to know all the pros and cons on its useage from those of you who use one. I understand it measures in brix.
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I use one

Postby dartedplus » Mon Jan 20, 2003 8:17 am

i use one that i got on ebay for about $12. yes it measurers in brix, but i have a chart to convert that to SG. most of the ones on ebay were used by mechanics to measure the amount of antifreeze in autos, these are fine, just make sure you get one that has the scale up to 32, mine only goes to 18 which is the equivilent of SG 1.064, so if i brew anything higher, it is off the scale.

one downfall is that once there is alcohol in the solution, you need to use some formula to figure out the SG, which Mesa said he would forward to me but hasn't yet (hint, hint)

it is nice to be able to just put a couple of drops on it and be able to check the SG without filling a tube and using the hydrometer

ed
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Refractometers...

Postby Mesa Maltworks » Mon Jan 20, 2003 12:49 pm

I began using refractometers for all gravity measurements when I was a homebrewer. I always hated that I had to loose such a "big" amount of beer to take daily gravity readings. After I returned from the UK, I at least had a mini-hydrometer to use (around 1/2 the size of the typical hydrometer), but I still wished for a better device. Enter the refractometer ! The sample size is tiny, so it was an answer to my prayers.

Prior to the onset of fermentation, the readings may be converted directly to Plato (Brix/1.04=Degrees Plato). You can loosely convert plato into SG by multiplying by 4, but this is not completely accurate since the relatinship between SG and Plato is not linear and the higher the SG, the less linear the relationship becomes. Conversions from Plato to SG are most accurately done using a computer program that has factoring algorythms in it to account for this deviation.

Once fermentation has begun, the readings cannot be used directly to assess fermentation progress. This is because of the way they work, by using the refraction of light to gauge sugar content in water. Once fermentation has begun, alcohol is present which effects the refraction causing a misread. There are conversion calculations available that are accurate enough for home brewing use, but they are laborious to use manually. It is best to take the calculations and enter them into a spreadsheet program such as Lotus or Excel to cut down on time and errors. They can also be entered into a programmable calculator, although I have not tried it. If anyone wants these calculations, I can post or forward them upon request.

Another reason I like them is that they are easier to read than a hydrometer. In the pro-brew setting, I have had my assistants take gravity readings on a daily basis using both devices. Rarely ever did their measurements differ when using a refractometer, but when using a hydrometer, the readings differed frequently. I solved the hydro misreads thru training, but I still prefer refractometers for consistency.

I use refractometers currently in my brewery, but I no longer use the manual equations for conversions. I use ProMash to do this for me and have found it to be even more accurate than the manual calcs. I have not seen the Beer Tools product for brewing management, it may have such a conversion built in as well. I recently downloaded a Brix to Plato converter that runs on my Palm Pilot but have not used it yet to compare it's results.

Remember, Brix scale hydrometers come in different ranges due to their primary use which is in the fruit juice industry. Make sure to purchase one with a 0~32 Brix range so you can cover the complete spectrum of beer and wine starting gravities. Also, it has been a while since I've seen one that wasn't, but make sure to get one that is ATC (automatically temperature compensated) so that you don't have to adjust the readings based upon the sample temperature via manual calculations.

Eric
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BUSTED !!!!....

Postby Mesa Maltworks » Mon Jan 20, 2003 12:55 pm

Whoops ! Sorry ED... I thought I sent the formulae for refractometer conversions to you, but evidently I didn't. I will dig them back up and do so. I will have to e-mail them though because the forum does not have the ability to display exponential figures. What format do you want it in ? I use MS-Word.

Post back and I will come through... I promise !

Eric
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word is fine

Postby dartedplus » Mon Jan 20, 2003 2:20 pm

ms word will be fine, please send to edthedart@netscape.net, there is a possibility that you did send it and I didnt get it, sometimes netscape sucks
thanks eric
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The formulas

Postby jeff » Mon Jan 20, 2003 6:47 pm

If you have a moment to post the formulas, I might be able to incorporate them into the tools at this site. Any help is appreciated, thanks.
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Regression Formulae for Refractometer Use....

Postby Mesa Maltworks » Thu Jan 23, 2003 7:21 am

Regression Formulae for Refractometer Use
After the Onset of Fermentation

NOTE: Since the forum cannot display exponents... Where a number is displayed after an abbreviation (EX:R2) it is indicating either to square the value or cube the value (EX:R3)


1. Alcohol By Volume

ABV=(277.8851-277.4(SG)+0.9956(R) +0.00523(R2)+0.000015(R3)) X (SG/0.79)

2. Specific Gravity

SG=1.001843-0.002318474(OG)-0.000007775(OG2)-0.000000034(OG3)+0.00574
(R)+0.00003344(R2)+0.000000086(R3)

Accuracy: .2
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Many thanks!

Postby jeff » Thu Jan 23, 2003 10:05 am

I can see where obtaining a result by hand would be impractical to say the least. Thank you for your assistance, I will see what I can do to implement an easy to use tool for performing these calculations; since refractometers are gaining more popularity among homebrewers.
--
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