OG too high for refractometer... Advice needed

[Tyler B]

Hello fellow Brewers! I brewed my biggest beer to date but unfortunately gravity was way too high for my refractometer and I don't have a hydrometer.

My work around... Add 125mL of wort to 125mL of water and measure. The 250mL sample measured 14 Plato (1.057 SG after conversion) on my refractometer.

Do you know if there is an online calculator or an equation I can use to calculate my actual gravity? Can I just double the diluted number and call it something like 1.114? Or does the weight of the sugar in the water (vs plain water) completely mess that up?

Ive already pitched yeast so it's too late for any more measurements/data beyond what I have. Thanks in advance, your help is always appreciated!

 

[bruce_the_loon]

There is a dilution calculator at Dilution And Boiloff Gravity Calculator - Brewer's Friend that if you put 250 in the initial volume, 125 in the target volume with 1.057, it returns 1.114. So it does appear to be a direct linear relationship.

 

[Tyler B]

Thanks for the link, Bruce! I saw that earlier and came to the exact same conclusion... Until I found another forum discussion where people said you had to use equal masses of wort and water (not equal volumes).

I was hoping someone could confirm one way or another. I suppose it doesn't really matter because fermentation is off to a good start and I'll have beer in the end no matter what the calculators say.

Interestingly, if you double 14 plato, you get 28 Plato (obviously) which is not equal to 1.057x2 or 1.114. Instead, 28 Plato is equal to 1.120 SG.

 

[VikeMan]

Yes, if you double the total volume by adding water, the gravity "points" are halved. So 1.114 becomes 1.057.

Until I found another forum discussion where people said you had to use equal masses of wort and water (not equal volumes).

If they were talking about SG, they were wrong.

Interestingly, if you double 14 plato, you get 28 Plato (obviously) which is not equal to 1.057x2 or 1.114. Instead, 28 Plato is equal to 1.120 SG.

Plato is a different animal. It's a measure of sugar mass per mass of wort. Specific gravity, OTOH, is a measure of sugar mass per volume of wort. (Technically, specific gravity is a measure of ratio of density of a solution to standard water density, but for beer wort, sugar mass per volume of wort is what drives the SG.)

Since sugar and water don't have the same volumes per mass as each other, not to mention that X volume of sugar + Y volume of water does not equal X + Y when dissolved together, the Plato and SG scales are not directly proportional to each other.

 

[Tyler B]

Thanks! Appreciate the response, very helpful. It looks like I can continue diluting my samples for high gravity beers to at least get me close enough.

 

[Smiling Frog]

Can I ask where you find a refractometer that reads in degrees Plato? The only ones I see read in Brix (or, maybe Brix and SG). I realize that Brix and Plato are essentially equivalent, but I didn't know there were any that read in degrees Plato.

Honestly, I believe refractometers should give you the actual refractive index. Perhaps with a Brix or SG scale for reference, but I would prefer an instrument that gives the actual value of the characteristic it is measuring.

 

[Tyler B]

Can I ask where you find a refractometer that reads in degrees Plato? The only ones I see read in Brix (or, maybe Brix and SG). I realize that Brix and Plato are essentially equivalent, but I didn't know there were any that read in degrees Plato.

Honestly, I believe refractometers should give you the actual refractive index. Perhaps with a Brix or SG scale for reference, but I would prefer an instrument that gives the actual value of the characteristic it is measuring.

https://www.brouwland.com/en/our-pr...actometers/d/refractometer-0-18-plato-0-1-atc
I live in Vietnam and it was the only one I could find when I bought it.

 

[Smiling Frog]

https://www.brouwland.com/en/our-pr...actometers/d/refractometer-0-18-plato-0-1-atc
I live in Vietnam and it was the only one I could find when I bought it.

Thank you. I have never seen these. Here in the US, the 0-32 Brix refractometers are more common, although they have a similar appearance. Although the Brix and Plato scales are slightly different, I consider them the same. Even the 32 Brix scale wouldn't read your wort, though.

 

[Vale71]

https://www.brouwland.com/en/our-pr...actometers/d/refractometer-0-18-plato-0-1-atc
I live in Vietnam and it was the only one I could find when I bought it.

That's a °Brix scale, the Brouwland description is just plain wrong except for pure sugar solutions where °Brix=°Plato.

 

[Tyler B]

That's a °Brix scale, the Brouwland description is just plain wrong except for pure sugar solutions where °Brix=°Plato.

Interesting! Not disagreeing with you, but how do you know? Would it be possible to attach a plato scale (with the appropriate conversions) on to a refractometer or no?

 

[Vale71]

First it does not say Plato on the scale. Secondly it is possible to attach a Plato scale to a refractometer but that would only be correct for a specific liquid which will need to be explicitly named. So a Plato scale for wine must would not work for beer or honey and vice versa. I don't see anywhere in the description or in the dowloadable manual (which only mentions °Brix BTW) for what type of liquid the alleged Plato scale would be valid.

 

[Tyler B]

I obviously don't know enough about how these numbers are calculated, conversions between them, etc. I had no idea. The packaging and the manual definitely says Plato so I just assumed it was Plato.

So I should be reading this as brix and converting?

 

[jseyfert3]

Honestly, I believe refractometers should give you the actual refractive index. Perhaps with a Brix or SG scale for reference, but I would prefer an instrument that gives the actual value of the characteristic it is measuring.

Yes, I want my flowmeter to output a stream of pulses instead of displaying gpm or lpm. And I want my gas tank in the car to display the height of the gas in the tank in rather than a scale from full to empty...

In all seriousness though, a quick search showed that you can get handheld refractometers that display in nD, but the cheapest my quick search showed was around $330, and I'm not sure that had a range suited to homebrewing.

 

[Smiling Frog]

I obviously don't know enough about how these numbers are calculated, conversions between them, etc. I had no idea. The packaging and the manual definitely says Plato so I just assumed it was Plato.

So I should be reading this as brix and converting?

Tyler B, for your purposes, the Brix and Plato scales can be considered identical. They are both defined by the specific gravity of a sucrose solution of the indicated weight percent. The major differences come from whether the standard is defined at 15.5C or 20C. You might think that temperature correction of the specific gravity reading would take care of that difference, but the temperature correction is based on (pure) water, not a sucrose water solution whose thermal expansion characteristics are dependent on the sucrose concentration. Very few hydrometers used by homebrewers have either the precision or accuracy to detect these differences. The scales are considered interchangeable because a 10% by weight solution of sucrose is going to weigh the same as a 10% by weight solution of "malt sugars" and using sucrose for the standard causes little error,

Things change when you use the refractometer as the optical properties of these sugars vary more than their weight does. Even with that, the error is small (generally less than 5%), but it is enough to notice. If you rely on the refractometer readings (and correct for alcohol content once fermentation has occurred), the refractometer readings should be accurate enough since they should be repeatable, but they will differ slightly from what you would get with a hydrometer.