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Home Brew Forums > Home Brewing Beer > Beginners Beer Brewing Forum > Why no adjustment
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Old 03-30-2012, 01:21 PM   #1
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Default Why no adjustment

When taking a refractometer reading once alcohol is present, it is necessary to use the OG and the refract reading to apply a correction factor to arrive at the correct SG reading. I assume this is because the optical properties of the wort/green beer are changed by the presence of *some* alcohol.

Why is a similar correction factor not required when taking a hydrometer reading?

Given:
OG 1.055
SG 2 weeks 1.030

May well have the same actual SG but render a different apparent reading due to less alcohol present as:

OG 1.040
SG 2 weeks 1.025

Am I missing soimething? This is a scholarly question.

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Old 03-30-2012, 01:38 PM   #2
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There are no optical qualities to adjust for in a hydrometer since it doesn't rely on optics for a readings.

It's only measuring the change in buoyancy of the hydrometer. A solution with more sugar will make a hydrometer float higher than one with less sugar.

The alcohol DOES change the properties in that a solution can have enough alcohol to make the hydrometer drop BELOW 1.000! That's less than pure water.

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Old 03-30-2012, 01:40 PM   #3
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Because of what they each measure. As you know, a refractometer measures the sugar in water by refracting light. That is why a refractometer is not susceptible to temp changes. A Hydrometer on the other hand measures solids in wort/beer by gravity. The alcohol has less weight then water. Hydrometers on the other hand are susceptible to temp changes. You can't take a hydrometer reading (accurately) with wort at over 70 unless you correct for the temp.

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Old 03-30-2012, 01:45 PM   #4
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Are you asking why you don't have to correct a hydrometer reading after fermentation has commenced? The way you worded this is very confusing...

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Old 03-30-2012, 01:49 PM   #5
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This is why I'm not convinced to buy a refractometer due to the correction factor needed to read when alcohol is present. Being new at this, I guess I'd rather keep it simple and not add a possible error factor when using the correction for alcohol being present.

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Old 03-30-2012, 02:00 PM   #6
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Quote:
Originally Posted by mtbcoach View Post
This is why I'm not convinced to buy a refractometer due to the correction factor needed to read when alcohol is present. Being new at this, I guess I'd rather keep it simple and not add a possible error factor when using the correction for alcohol being present.
In my personal opinion a hydrometer is practically a necessity, even for most advanced brewers. It's dead simple for both OG and FG readings.

However, I've personally had good results using my refractometer for all readings after comparing to my hydrometer.

I find the refractometer to be a VERY useful tool DURING the brewing, when I don't' want to wait for a large sample to chill to testing temp. I can draw a few milliliters of hot wort in a pippette and chill under cold water in a few seconds and take a reading. I can use that information for calulating if there are any adjustments necessary, like extending the boil, topping off, adding extract, or whatever.

It's also just plain faster and easier than chilling the amount of wort necessary to take a hydro reading. I wouldn't say a refractometer is a great tool for the beginner, but if you are already using a hydrometer, and want to make brewday a little shorter and easier, then IMO it's worth the money as a convenience upgrade.

For reading FG gravity it's less useful due to the conversion process, and also because it's just about as fast and easy to pull a sample using a thief since the temp is close perfect for a hydrometer.
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Old 03-30-2012, 02:31 PM   #7
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There is no correction with a hydrometer as all a hydrometer does is take a reading of the density of the solution it does not care if it is wort , alcohol or piss for that matter. A refractometer on the other hand measures the amount of light refracted over the lens and alcohol bends light at a different "angle" than a solution without so that is why correction is needed. simple answer.

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Old 03-30-2012, 02:35 PM   #8
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Quote:
Originally Posted by Homercidal View Post
In my personal opinion a hydrometer is practically a necessity, even for most advanced brewers. It's dead simple for both OG and FG readings.

However, I've personally had good results using my refractometer for all readings after comparing to my hydrometer.

I find the refractometer to be a VERY useful tool DURING the brewing, when I don't' want to wait for a large sample to chill to testing temp. I can draw a few milliliters of hot wort in a pippette and chill under cold water in a few seconds and take a reading. I can use that information for calulating if there are any adjustments necessary, like extending the boil, topping off, adding extract, or whatever.

It's also just plain faster and easier than chilling the amount of wort necessary to take a hydro reading. I wouldn't say a refractometer is a great tool for the beginner, but if you are already using a hydrometer, and want to make brewday a little shorter and easier, then IMO it's worth the money as a convenience upgrade.

For reading FG gravity it's less useful due to the conversion process, and also because it's just about as fast and easy to pull a sample using a thief since the temp is close perfect for a hydrometer.
I agree. And when a refractometer is most useful is when you're fly sparging a small grainbill.

The reason is that you don't want to oversparge- you want to stop when your runnings are no lower than 1.010. A refractometer makes that very easy.

I still use my hydrometer often, as the refractometer is not a replacement for it. It's like with cooking- adding on omelette pan doesn't replace a traditional skillet but instead gives you another tool to work with.
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Old 03-30-2012, 05:11 PM   #9
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Yup. Thanks. I do not plan on using the refractometer once the cap is on the pail. Hydrometer. It was very helpful with the accompanying calculations in tweaking the DME addition to get me to my desired OG. (I'm doing PM presently) Also, I noticed the line is clearest when the wort is not cloudy. Gotta find a simple filter to put over the eyedropper.

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Old 03-30-2012, 05:53 PM   #10
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I just want to add flame to the fire!

I haven't used my hydrometer in years. I just use the refractometer for everything and use the correction factor. However, I do still have a hydrometer...somewhere.

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