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Old 01-28-2013, 11:02 PM   #1
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Default Missing Gravity Points?!

Ok hopefully someone has the patients to follow me here cause this going to be long winded.
Quick note, took preboil gravity reading with refractometer with ATC calibrated with distilled water and my original gravity was with a hydrometer @ 65 degrees.

I got this Stone IPA recipe from Mitch Steele's new book.
Now this is only the 2nd all-grain batch on my new equipment and set up and I'm still fine tuning my numbers for Beersmith. I missed my OG in my first recipe by 4, and this time I was off by 9 and I can't figure out why.

Here is the recipe with Beersmith's estimated numbers are in italic and my numbers are in bold


All-Grain: Brewhouse Efficiency 73%
Yeast: White Labs English Ale Yeast - 2L starter

12lbs 12oz - 2 Row Pale Malt
14oz - Crystal 15L
.6oz Chinook - 90mins
.4oz Columbus - 90mins
2oz Centennial - 15mins

Mashed @ 149degrees for 60mins with 5.1gallons and batched sparged with 5.9gallons of 185degree water, which put the grain bed to 168degrees, for 10mins and then drained. Mash Ph was 5.6

Batch Size: 5.7gallons - 5.6gallons

Pre Boil Volume: 9.1gallons - 9.1gallons
Pre Boil Gravity: 1.045 - 1.041
Post Boil Volume: 6.82gallons - 6.4gallons
Original Gravity: 1.063 - 1.054

Now after I chilled it with my immersion chiller the volume dropped to 6.1gallons, which is calculated for in Beersmith, and I only got 5gallons into the carboy, so I ended up pouring the trub into my funnel that has a filter and squeezed out another .6gallons to reach my final batch size of 5.6gallons.

So far you can see that my boil off rate was off. I had it set for 1.5gallons/hr when I actually had 1.8gallons/hr, which you would think would make the wort more concentrated, but as you see that doesn't seem to be the case. And my trub loss was slightly off, but I don't see how either of those would lead to missing gravity points.
I did end up with less volume then expected, but even though I had to filter the trub to make up for some loss I don't see how that effects points either.

My preboil volume had 373points, but my final volume was only 302points. 71points gone?!
And Going back and looking at my first recipe on this set up and I seemed to be missing 45points in the difference between my preboil and post boil gravities.

My only guess is that my refractometer may have been off with my preboil reading or its broken haha. I stirred up the wort before taking a reading.
When I took my gravity reading after I cooled and transferred to the carboy the refractometer was reading only 1.049, but my hydrometer (which I have trusted for awhile) was reading 1.054. So I really don't know what to say about that.
Anyway to test a refractometer with anything else, such as plain sugar water?

I know my final volume was off, but that to me only seems to be from miscalculating my boil off and trub loss. But, my starting volume was right and a lower final volume would make you think I should have a higher OG then I do.


Now I know this will throw off the hop to malt profile of the final beer, but its a Stone IPA clone so more hop bite may not be a bad thing.
But another concern may be over pitching since I made a 2L starter from Mr.Malty's calculator for a 1.063 beer, but I only hit 1.054. I had a krausen forming after only 6 hours and 48hours later the krausen has completely fallen back and there is just some yeast clumps floating on top now.
I know it will still make beer, but this is driving me nuts on why I'm not hitting my numbers.

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Old 01-28-2013, 11:26 PM   #2
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I'm going to ignore your pre-boil numbers for a second and focus on post-boil.

There's something seriously wrong here. Both your recipe and you ended up with 9 gallons pre-boil, the example system that the recipe was built from boiled off LESS liquid than you did and ended up with a higher gravity?!?! Either their recipe specs are screwed up or one of your measurements is.
The recipe had an evaporation rate of 1.52gallons / hour and you had an evaporation rate of 1.8 gallons / hour, is that right?


Definitely calibrate that refracto meter with several water and sugar concentrations to get a 1.020, 1.040, 1.060, & 1.080 gravity sugar solution and then test it.

Something just isn't right here.

Adam

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Old 01-28-2013, 11:36 PM   #3
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Quote:
Originally Posted by biertourist View Post
I'm going to ignore your pre-boil numbers for a second and focus on post-boil.

There's something seriously wrong here. Both your recipe and you ended up with 9 gallons pre-boil, the example system that the recipe was built from boiled off LESS liquid than you did and ended up with a higher gravity?!?! Either their recipe specs are screwed up or one of your measurements is.
The recipe had an evaporation rate of 1.52gallons / hour and you had an evaporation rate of 1.8 gallons / hour, is that right?


Definitely calibrate that refracto meter with several water and sugar concentrations to get a 1.020, 1.040, 1.060, & 1.080 gravity sugar solution and then test it.

Something just isn't right here.

Adam

Yeah that's what I can't figure out. I'm thinking it must be the refractometer.
Definitely going to take a sample from the kettle and cool it before the boil next time and compare it to my hydrometer reading.
My evapo rate was 1.8gallons/hour.

What kind of sugar should I use for the concentrations? Just corn sugar?
And I'm guessing heat it up so it dissolves into the water?
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Old 01-29-2013, 04:23 PM   #4
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Table sugar is cheapest and you're going to be throwing it away so just use table sugar.
Heat it only as much as you have to because you want the measurements at 62F as most hydrometers are calibrated @ that temp.



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Old 01-29-2013, 05:47 PM   #5
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I'm assuming your refractometer reads in Brix. If so, you can check it's accuracy by dissolving some table sugar in water, taking a reading with the refractometer and checking against the hydrometer, then diluting the sample with some water, and repeating the test.

If you start with 90g table sugar, and 210g water, you can dilute the sample by adding 60, 90, 150, 300, and 900g water (where g = grams not gallons), you should end up with results similar to the following

Code:
Sucrose Water   Brix    Gravity
  90g    210g   30.00   1.129
  90g    270g   25.00   1.106
  90g    360g   20.00   1.083
  90g    510g   15.00   1.061
  90g    810g   10.00   1.040
  90g   1710g    5.00   1.020
How are you converting the refractometer readings to gravity? Beersmith provides a refractometer tool, but for accurate results you need to calibrate the Refractometer Settings. If you use an on-line converter, they are usually set up for fruit juices, and they will introduce an error if used for beer.

Hope this helps.

-a.
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Last edited by ajf; 01-29-2013 at 05:52 PM. Reason: Re-arranged code
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Old 01-29-2013, 07:02 PM   #6
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My refractometer actually has both brix and specific gravity scales on it.
Definitely going to test it against my hydrometer readings with sugar water.
My preboil gravity readings must have been off on brew day

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Old 01-29-2013, 08:27 PM   #7
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If your refractometer has both scales, then the gravity scale is probably calibrated for wine rather than beer. If this is true, and you compare the refractometer against the hydrometer using a sugar solution, then (assuming both instruments are accurate across the full range) you should see no difference between the two instruments. However, if you are making a beer, the conversion from Brix to SG needs to be adjusted to account for the maltose in the solution, rather than just sucrose. Have a look at your Brix and SG scales. If 20 Brix corresponds to 1.083 SG, then the SG scale is calibrated for wine and should not be used for brewing. If 20 Brix corresponds to 1.080 (or slightly lower), then the SG scale is calibrated for beer, but won't be accurate for making wine.

If you repeat the experiment that I detailed before, but use DME instead of sucrose, you should get some different results. I think (but am not sure) the gravities should be the same (measured with the hydrometer), but the measured Brix values should be different.

If you use the Beersmith Refractometer Tool, you should calibrate the refractometer settings based on a batch of beer, and not sugar.

-a.

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Old 01-29-2013, 11:04 PM   #8
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This is the refractometer that I have
http://morebeer.com/view_product/18739
So I'm hoping morebeer isn't lying about it.
I'll test it out tomorrow when I have time and will report back on my findings\

Update
Ok so looking at the refractometer it has 20Brix aligned with 1.083
And I'm slightly confused cause according to Beersmith 20brix is 1.081, but I keep seeing conversion charts on different brewing websites that says it is 1.083. But Palmer's book also has a plato conversion chart and 1.083 is 20plato not brix so now I think morebeer is wrong with their refractometer.
I just contacted morebeer to see what they have to say about it.

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Old 01-30-2013, 01:23 PM   #9
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This was morebeer's response:

"Thanks for the inquiry. With the current ones we carry the 20 brixs mark align to 1.083 gravity as with yours, which appears to be correct while testing a hydrometer and a refractometer side by side. There are no specific wine refractometers since they all the measure the same thing, the refraction of light due to density of sugars in solution. What readings are you getting in comparison to your hydrometer? The main purpose of a refractometer is to determine if gravity adjustments need to be made during hot side brewing. To be completely accurate, it's still best to go with a hydrometer. The refractometer helps give you a ballpark range if preboil gravities changes need to be made before boil."

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Old 01-30-2013, 10:53 PM   #10
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I agree that there are no specific wine refractometers, but they are selling a dual scale refractometer, and the SG scale would match the Brix scale only if you were making wine, and not if you were making beer. However, if the Brix scale is accurate, you can ignore the SG scale and use the BeerSmith refractometer tool to perform the conversion after you have measured and specified the Brix Correction Factor.
I am somewhat amused by the paragraph headed "Getting Geeky about why the Specific Gravity Scale on our unit is accurate"
They completely forget to say that the SG scale on the hydrometer will not be accurate if measuring wort. It will be about 2 - 6% inaccurate depending on the composition of the wort. Don't take my word for it. Make a table sugar solution and measure the gravity with the refractometer and an hydrometer. The two readings should be identical (assuming both instruments and your readings are accurate). Then try the same experiment using a sample of wort (either using extract, or mashed grains). The refractometer will report a higher gravity than the hydrometer.

-a.

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