refractometer calcs- can this be right?

[Hopleaf]

I'm brewing a holiday spiced ale with OG of 22P (1.088)

It's fermented for 3 weeks and I just took a reeading and it's 9P.

Using this calculator:

http://brew.stderr.net/refractometer.html

That puts me at 1.004... 11.2 % ABV!!! Had been shooting for 8.3...

I used a 1/2 gallon starter + another smack pack of Wyeast 1007 German Ale.. I pitched the amount mrmalty told me to.. assuming I did that correctly.

Is this right??

 

[StewJo]

I plugged your values into the spreadsheet provided by MoreBeer and got very similar figures.

11.2% ABV? wow.

 

[Funkenjaeger]

I wouldn't necessarily trust it. I was really excited to use my refractometer during fermentation using the calculator in beersmith, but my experiments didn't show it to be very reliable. It never seemed to agree with my hydrometer in side-by-side tests after fermentation had begun. I think since the ingredients in beer vary so much, and refractometers are designed for simple sugar water only, it's tough for it to be all that accurate.

At least do a sanity check with a hydrometer.

 

[Hopleaf]

The thing was a volcano the day after pitching, lost almost a gallon to blow off. I'll be interested to see what the hydrometer says... I bottle in a week so I'll check it then and follow this up.

 

[TexLaw]

You can't use your refractometer after fermentation. It's calibrated to measure the concentration of sugar in a water solution, but you now have a water and ethanol solution. Your readings are way off.

There is a formula out there to calculate your actual gravity at this point, but it's much simpler to just take a hydrometer reading.


TL

 

[killian]

check out www.morebeer.com they have a spread sheet that Im thinking about trying

 

[the_bird]

You can't use your refractometer after fermentation. It's calibrated to measure the concentration of sugar in a water solution, but you now have a water and ethanol solution. Your readings are way off.

There is a formula out there to calculate your actual gravity at this point, but it's much simpler to just take a hydrometer reading.


TL

Yup. Doesn't look like that calculator is for use post-fermentation. I think there's a way of doing a conversion in BeerSmith and/or ProMash, but I haven't played around with it (no refractometer), and I'm not sure whether it's truly accurate or not.

Time to bust out the old hydrometer!

 

[Brewing Clamper]

Does your refractometer read in Plato? I thought they all read in Brix. Do you know what the brix reading was?

 

[ebeer]

Here is my calculator.

 

[killian]

Here is my calculator.

the two compared are real close( more beer and your's)

 

[Hopleaf]

Does your refractometer read in Plato? I thought they all read in Brix. Do you know what the brix reading was?

You are correct, I indeed meant Brix, not Plato.

I used that site because it was giving 'Corrected Specific Gravity'. I've read that many differing opinions that one can and cannot use a refractometer for SG readings.. I'll sanity check it this weekend with the hydrometer but it will be off since added 1/2 cup vodak with spices last night. Should definitely be ballpark though and if it's ~8.3% than I'll know for sure.

I popped it into ebeer's calc and it came up with similar (nice calculator btw ebeer).

 

[Funkenjaeger]

You can't use your refractometer after fermentation. It's calibrated to measure the concentration of sugar in a water solution, but you now have a water and ethanol solution. Your readings are way off.

There is a formula out there to calculate your actual gravity at this point

The original poster already indicated that he's using a calculator to handle that.

My point was, there are various calculators out there (web based, the one in beersmith, the excel spreadsheet ones, etc) but they all work basically the same - I have heard people recommend them but I have never heard of any positive results.

When I tried it using the beertools calculator, it would get me somewhat close to the actual post-fermentation hydrometer reading but it was quite often off by several points, which just isn't accurate enough. Beersmith has a calibration feature where you can mix up some "reference wort" and measure it side by side with both hydrometer and refractometer to calculate some internal scaling factor that it uses, but no matter how much I screwed with it I could never get a post-fermentation refractometer calculation to agree with the hydrometer on multiple batches.

Although there are a whole bunch of various calculators out there (web based, brewing software, excel spreadsheets, etc) and they usually seem to agree with one another, in my experience they do not agree with the hydrometer - so either I was doing something horribly wrong, or all of the calculators are wrong in the same way.

Hopleaf, I am interested to see whether you find the hydrometer reading to agree in the case of your current beer, after running it through several calculators.

 

[Hopleaf]

FYI, tried the spreadsheet at morebeer and got same numbers...

http://morebeer.com/learn_vids/vids_refract

 

[Hopleaf]

Bah I forgot about measuring.. I bottled two batches that day and was tired.. I suppose I can measure it in a few weeks and see what the ballpark is...

 

[boo boo]

Does your refractometer read in Plato? I thought they all read in Brix. Do you know what the brix reading was?

Plato = Brix. You can use them interchangeably.

I just use my hydro to measure after fermentation is complete.

 

[Vels]

When using the Alc% calculator in Promash

22 to 9 P
is 1.092 to 1.036
Equals 7,5%abv