Don't use a Refractometer for FG readings. Your beers didn't stall at 1.024.

[ajdelange]

I'm relying on memory here and it was a while ago but I can safely say that I wouldn't have been doing that. I would have been looking at the relationships between NI, OG and ABV and NI, OG and AE or TE for several beers to see if were possible to take a refractometer reading and turn it into an ABV and/or AE value without having to do what the ASBC recommends i.e. do a calibration curve using much fancier equipment for each beer or class of beers. I recall deciding that it wasn't doable and so stopped pursuing it. I can't turn up my notes on a cursory search so I'm afraid I can't give you a much better answer than that for the moment. I do clearly remember the NI vs temp. issue but not much else.

 

[stpug]

Updated my table here with sample readings from my semi-big, malty saison (Winter Starlight Saison).

Just to note: this saison did not finish as low as I had expected it to and had an unusually bigger body than expected, therefore I thought it would be a good candidate for comparison because of the perceived residual sugar and thick mouthfeel. I notice that of all beers I've sampled that this one has the most variance in calculated SG between beersmith and seanterrill (4 points, basically). I think that 4 points is significant because in this beer it is almost 1% ABV difference. One interesting point is that the hydro readings basically split the difference of the 4 points making each only about 2 points away which I find to be much better margin of error. Anyway, just thought this was worth mentioning. Again, I'll keep trying to add to this as I remember and have the time.

 

[thadius856]

I'm relying on memory here and it was a while ago but I can safely say that I wouldn't have been doing that.

Wouldn't have been doing what?

Were you not measuring in Brix? The SG scale on this style refractometer is way off on its own.

 

[ajdelange]

What are you using for Brix to SG correction when alcohol is present?

I'm relying on memory here and it was a while ago but I can safely say that I wouldn't have been doing that.

Wouldn't have been doing what?

Calculating SG from Brix.

Were you not measuring in Brix?

No, NI, refractive index.

 

[Kalvaroo]

OP here...

Thanks for all the input... I think i'm just going to stick with using a hydrometer for my final readings for right now instead of doing the conversion. I'll play around with using brix and doing the conversions on my next batch and see how it goes.

Here's my numbers so you guys can keep playing around with the math... if you want. Notice how my refractomter readings for final gravity were different, but the same when measured with a hydrometer.

What I was shooting for:

Pale Ale: 5.5% ABV / OG 1.054
DIPA: 7% - 8% ABV / OG 1.065 - 1.075


What I got for Original gravities: (Measured with Refractometer, right before pitching yeast)

Pale Ale: 1.054
DIPA: 1.065

Final gravities: (Measured with Hydrometer)

Pale Ale: 1.012*
DIPA: 1.012*

*Someone implied that i don't know how to read a hydrometer. Both were read at the bottom of the meniscus... If they were read at the top I would've put them at around 1.010 - 1.011. The top of the meniscus in the picture i posted was at around 1.0105.

Final gravities: (w/Refractometer)

Pale Ale: 6 Brix 1.024 SG
DIPA: 7.5 Brix 1.029 SG


I pretty much got what I was going for... I just freaked out for a second when I initially tried to take FG readings with a Refractomter.

 

[stpug]

Final gravities: (Measured with Hydrometer)

Pale Ale: 1.012*
DIPA: 1.012*

Final gravities: (w/Refractometer)

Pale Ale: 6 Brix 1.024 SG
DIPA: 7.5 Brix 1.029 SG

The corrected final gravities for your refractometer readings would be:
Pale Ale: 1.005 SG (BS) or 1.0096 (ST)
DIPA: 1.007 SG (BS) or 1.0114 (ST)

...which still would not be right unless you were brewing with saison yeast .

I would agree that in your case you are better off using a hydrometer for your readings because your hydro vs refract final gravities are starkly different (with the exception of "DIPA refract ST" reading). I'm not finding this kind of variance in my sample testing with my equipment and I cannot explain why such a difference.

 

[thadius856]

The corrected final gravities for your refractometer readings would be:
Pale Ale: 1.005 SG (BS) or 1.0096 (ST)
DIPA: 1.007 SG (BS) or 1.0114 (ST)

...which still would not be right unless you were brewing with saison yeast .

I would agree that in your case you are better off using a hydrometer for your readings because your hydro vs refract final gravities are starkly different (with the exception of "DIPA refract ST" reading). I'm not finding this kind of variance in my sample testing with my equipment and I cannot explain why such a difference.

Where'd you get these numbers?

For the Pale, I get OG 13.95 Brix, FG 6 Brix. Converted FG 1.0095, 5.7% ABV/4.5% ABW.

For the DIPA, we don't really know the OG. At 1.0119 converted FG and 7.5 Brix FG measured, I come out with 16.1 Brix OG (1.0632). This one's a little too fuzzy without a measured OG to trust, though.

 

[ajdelange]

The explanation is that there is no accurate 'rule' that maps pre and post fermentation Bx readings into a FG reading for all beers. If you 'plot' SG vs the original Bx and final Bx for a whole lot of beers you will find the points more or less describe a surface and you can do a two dimensional curve fit to that surface and the majority of the points will lie close to the surface represented by the curve fit but some will be quite far off. It is in the nature of beer.

 

[stpug]

Where'd you get these numbers?

For the Pale, I get OG 13.95 Brix, FG 6 Brix. Converted FG 1.0095, 5.7% ABV/4.5% ABW.

For the DIPA, we don't really know the OG. At 1.0119 converted FG and 7.5 Brix FG measured, I come out with 16.1 Brix OG (1.0632). This one's a little too fuzzy without a measured OG to trust, though.

I used the OPs SG numbers (1.054 and 1.065). Then using their photo in the original post, I tried to determine a brix % (13.8% and 16.6%, respectively).

Using the starting gravity/brix and finishing brix, I implemented beersmith's (BS) calculator and SeanTerrill's (ST) calculator.

The really low numbers were produced by BS calculator and the more reasonable numbers were produced by ST calculator.

 

[thadius856]

Then using their photo in the original post, I tried to determine a brix % (13.8% and 16.6%, respectively).

His OG was taken with a hydrometer, not a refractometer, so you can't sight across the scale he pictured.

 

[iaefebs]

This is why I've reduced my argument to "try it for yourself". If you have a hydrometer tube of beer and you are satisfied with your hydrometer reading. When you are done with that test pull a couple drops from the tube and check with your refractometer. Use a calculator and decide for yourself. I don't think the extra step will take you but a minute. This post has a lot of discussion but has two photographic documents. Pic one is the dual scale refractometer that is obviously a flawed piece of equipment. Picture two shows the hydrometer floating in the beer with at least two interpretations of what it reads.

 

[Kalvaroo]

OP here again...

For your enjoyment below is a picture of the scale on my refrac. I originally went with the SG on my refrac for OG's, like i said before, i just started using it and hadn't gotten into using the Brix scale. So using RefracTool on my phone, i can enter them in a couple ways and get different results. I can enter into the conversion tool using the SG i originally got, which gives me a different Brix reading than what reads on my refrac, or i can use the brix reading from the picture below and enter that in to the RefracTool. If that makes sense. Either way you look at it, with more conversions in a calculation, the more room for error.

I just spent the last hour messing with the numbers and i'm getting favorable results. My beers turned out where i wanted them to. The PA is exactly where i wanted it, but i've been brewing that one for a few years now with very similar results every time. The DIPA was in the range of where I wanted it, but i'm not a perfectionist... just a brewer.

I know my FG on my DIPA is strange (when using the refrac), but it's still telling me there's a higher alcohol content in the DIPA. Which makes sense.... I'd have to ask a science major on how alcohol affects the refraction in a refractometer, I'll just hit the "I believe" button for now, and know that it does.

I'll check the FG on the DIPA again tonight with both the refrac and hydro. When I think back, the line on the refrac wasn't super fine. I took a look at it this morning and it looked like it cleared up even more than it had been before, so there may have also been a lot of yeast still in suspension. The PA is kegged and conditioning... I left the DIPA in the primary to give it a little bit more time, to taste, and possibly dry hop again.

Here's some additional info on my process with these beers for a little bit more fun.

Attenuation on my Pale Ale: Apparent: 77.78% Actual: 63.31%
Attenuation on my DIPA: Apparent: 81.54% Actual: 66.37%

Yeast For Both: WLP001 CA ALE (White Labs)

What I pitched,

In the Pale Ale I pitched a fresh (from vial) 1L starter made with Light DME 48 hrs. prior. I used a stir plate. Made it Friday night, pitched Sunday evening. Added 1 minute of O2, Lag time about 6-8 hrs.

In the DIPA, I used half the yeast cake from my previous pale ale batch brewed 20 days earlier. I left about a cm of beer on top of the yeast cake when i racked, swirled it up and dumped half down the drain before i ran my wort into the carboy. Added 1 minute of O2, Lag time about 1-2 hrs, and a very vigourous fermentation.

I ferment in an upright freezer, with a johnson controls currently set to heating using a lightbulb. with the temperature maintained at 67.

Grain for my PA was crushed by my local homebrew shop. Grain for my DIPA was crushed by myself using my new grain mill, and it was a little finer than it shoud have been. Also, I brew on a RIMS system, and when I was mashing my DIPA the return valve got clogged so i turned off the burner and pilot and my mash ended up resting at around 140 for 25 min before i started recirculating the mash at 150. I ommited the 25 minutes and continued the rest for another 60 min. I also always check for complete starch conversion with iodine and try to stop my runnings around 1.010.

 

[Kalvaroo]

Picture

 

[stpug]

...

I'll check the FG on the DIPA again tonight with both the refrac and hydro. When I think back, the line on the refrac wasn't super fine. I took a look at it this morning and it looked like it cleared up even more than it had been before, so there may have also been a lot of yeast still in suspension.

...

I run into the same non-super fine line issue when taking readings. I've found that I see three shades of color when looking at a sample; light blue/white, grayish, dark blue/gray. The grayish color is a very thin area between the other two colors and varies by sample, but is always on the thin side. I take my reading from where the dark blue/gray ends. Whether or not this is correct is another question

Thin grayish area in the example below is exaggerated to show where I take my reading from:

 

[jwalker1140]

Interesting. I've always taken my readings from the center of the (sometimes) fuzzy line. I think I've always done it this way because I assumed this is where the line would be if it wasn't made fuzzy from the solids suspended in the sample.

But I guess this could be the equivalent of taking a hydrometer reading from the middle of the meniscus line rather than the bottom. I wonder if I've been underestimating my gravity all these years....

 

[stpug]

Honestly, I don't know .

My brain tells me that the dark (upper) color is sugar, and the light (lower) color is not. I've made the assumption that the gray matter in between is something else (solids, dextrins, hop additions, oils, maltose-error, starch, ???, etc.) and therefore not the reading I'm after. Generally the difference between the middle of the grayish area and the dark blue is <0.2 brix, so nothing too huge.

I DO find the grayish area on my refract to be a bit gradient whereas the dark blue has a distinct boundary. This also leads me to believe the distinct boundary is the place to take my reading from.

I have noticed that fresh squeezed grape juice and honey solution do not exhibit this gray area, or if so then it's so extremely thin it's unrecognizable. Probably relates to the sucrose vs maltose sugars viewed in a refract.

 

[jwalker1140]

I have noticed that fresh squeezed grape juice and honey solution do not exhibit this gray area, or if so then it's so extremely thin it's unrecognizable. Probably relates to the sucrose vs maltose sugars viewed in a refract.

I'm not sure it has anything to do with the type of sugar. I use my refractometer with wine making and I get a real sharp line when I take a reading from freshly squeezed grapes before fermentation starts (kind of like the sharp line I usually get when I take a preboil reading) and after fermentation has finished and the wine has started to clear. The line get's VERY fuzzy (2-3 brix, easy) during peak fermentation when a lot of yeast and solids from the grape skins are in suspension.

I would still like to hear from someone more knowledgeable than me on where to take a reading, though stpug, your reasoning makes sense to me.

 

[stpug]

After a little reading it seems that it may in fact be particulate/solid matter, and a simple solution to sharpen the line is to rotate the lens so it's toward the ground which helps the particulate matter fall away from the lens. Another idea that was mentioned was to physically push down on the clean lens cover to squish down the sample. Easy enough ideas to try I suppose.

 

[jwalker1140]

I've tried both of those, and they help a tiny bit. I've had better luck running my sample through some sort of filter, like a paper coffer filter or a super fine mesh tea bag strainer.

 

[stpug]

I've tried both of those, and they help a tiny bit. I've had better luck running my sample through some sort of filter, like a paper coffer filter or a super fine mesh tea bag strainer.

Very good! I'll try all of these ideas myself to see what helps me the best. I recall straining my wine samples through coffee filter when I was taking readings and it helped a lot.

 

[ajdelange]

Clearly that scale is off too. As it is plainly labeled 'wort' one must assume that the ASBC tables should apply. In the ASBC tables
SG °P
1.030 7.56
1.040 9.99
1.050 12.39
1.060 14.74
1.070 17.06
1.080 19.33

I'm not a science major but the reason alcohol make the Bx reading higher is that alcohol has a higher refractive index than water just as sugar has a higher refractive index than water.

The dark and light areas you see are dont correspond to sugar and not sugar but to angles above and below the Brewster angle i.e. the angle beyond which light is entirely reflected from an interface between two media with different indicies of refraction. As the Brewster angle depends on the ratio if the indices of refraction the index of refraction for the solution can be determined from that angle as the NI of the glass in the prism is constant. As the NI of a solution depeds on the concentration of things dissolved in it (and what they are) Brewester angle, as observed through the refracl. eyepiece can be calibrated in Bx.

The line should be reasonably sharp. I expect where it isn't it is the result of scattering by yeast cells, trub particles... Filtering or centrifugation of the wort might help.

In internal (digital) refractometers the angle of the beam within the prism is measured, not light that crosses over into the beer so these should be better immune to this phenomenon.

 

[TyTanium]

^^Smart

It's amazing to me how many dual scale refracts have the wrong scale on them. Even ones that say they are "corrected" from the faulty scale still have the wrong scale.

 

[TyTanium]

AJ - what formula do you use to convert Brix to SG for wort? or wine or mead?

I've been using the Lincoln equation assuming P & Bx are close, but I'm sure that's prone to systematic error

 

[ajdelange]

I use the ASBC polynomial

°P = ((135.997*S -630.272)*S + 1111.14)*S - 616.868

Right or wrong, this is 'official' but it fits the data in the Plato Commission table quite well. The Lincoln equation is actually pretty close to this and appears to be a second order fit to the same table.

There is more detail on this than you probably want to know about (including comparison of the Lincoln equation to the table) in this pdf: http://www.wetnewf.org/pdfs/Brewing_articles/Sugar_Gravity.pdf

 

[TyTanium]

Thanks! Some nice bedtime reading.

What about brix to plato? And isn't there some 1.04 refract correction for matose vs. sucrose with most refractometers?

 

[Kalvaroo]

In internal (digital) refractometers the angle of the beam within the prism is measured, not light that crosses over into the beer so these should be better immune to this phenomenon.

I decided to look up digital refractometers, and ran across this article from yesterday:

http://www.prweb.com/releases/prweb2013/3/prweb10453143.htm

I'm not about to spend $300 on one of those... just thought it was interesting.

 

[Kalvaroo]

Guess my DIPA had a couple more points to go. Here's my final results.

 

[ajdelange]

If I'm working with beer I use the ASBC polynomial. If I'm working with anything else I use the ICUMSA polynomial. They make no distinction between Brix and Plato - in fact they don't even mention them. They compute the density based on grams/100 grams. Period. For Brix there are the NBS tables. Here are some comparisons of the apparent specific gravities computed for 10 g/100 g (10Bx, 10 °P)

&#8226;print BxNBStoS(10)
1.04003
&#8226;print Plato2Sg(10)
1.04003
&#8226;print DensA(10,20,1,0)
1.04003

Not much difference at 10 °P.

Here are refractive indices (absolute, 20°C) for 4 sugars
&#8226;print sucRIa(10,20,589.3,0,0) Sucrose
1.34819
&#8226;print sucRIa(10,20,589.3,1,0) Glucose
1.34811
&#8226;print sucRIa(10,20,589.3,2,0) Fructose
1.34801
&#8226;print sucRIa(10,20,589.3,3,0) Invert Sugar
1.34805

Maltose is not on the list but given that it is two glucoses and the differences between sucrose I'd guess maltose to be around 1.34815. Not nearly a 4% difference.

 

[thadius856]

OP here again...

For your enjoyment below is a picture of the scale on my refrac. I originally went with the SG on my refrac for OG's, like i said before, i just started using it and hadn't gotten into using the Brix scale.

If those OG's were taken using the SG scale on your refrac, we can't trust them. Sorry, the OG scale on these things is garbage. We can sight across the picture and pretend that we know what the OG is in Brix, but that's not really accurate to the point we can make judgments about 1-2 point differences.

Look at your pictures. The one on your phone shows 1.120 is 28.2 Brix. The one in your refrac shows 1.120 is about 31.0 Brix.

 

[thadius856]

Woops, yeah, that's what I meant.

Wish I had a refrac that could go to 1.200. Would be good for Barleywines.