Refractometer software, WARNING!

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boingy

Re: Refractometer software, WARNING!

Post by boingy » Thu Jan 12, 2012 6:53 pm

gregorach wrote:But what about us data junkies?
Heheh. I would have though as a data junkie you should be using a hydrometer in preference anyway. I'd be tempted by those narrow scale ones that someone linked to a while back (maybe Aleman?). Each one covers a reduced range so it's easier to read small changes. I seem to recall they were also pretty large so they needed a large trial jar and also that they commanded a higher price. (A quick search failed to find the post I'm thinking of...)

andybiochem

Re: Refractometer software, WARNING!

Post by andybiochem » Thu Jan 12, 2012 6:54 pm

Martin G wrote:Just a thought and I stand to be corrected but isn't there a dilution of the sugar solution when the gin is added? It looks to me like 84ml of solution is diluted to 100ml. So instead of;

(94*1.030 + 6*0.789)/100 = 1.0155

it should be more like;

(94*1.025 + 6*0.789)/100 = 1.011

There you go data junkies, have a think about that and rip it appart!
I guess technically it'd be more like:

((84*1.030) + (6*0.789) + (10*[???]))/100

Where [???] is the density of whatever the Vodka solute is, water perhaps? who knows!.
Either way, it's a guesstimate as I don't think you can just add densities in this way with ethanol.

Interesting stuff!

Manx Guy

Re: Refractometer software, WARNING!

Post by Manx Guy » Thu Jan 12, 2012 8:24 pm

boingy wrote:I have a much more pragmatic solution to this particular problem - I don't use the refractometer once fermentation has started.
Once you are familiar with your process you can get pretty good at estimating when fermentation is done. At that point the 100ml hydrometer sample gives you a perfect excuse for a crafty first snifter of the beer.
Runwell-Steve wrote:I often can't be bothered to get the refractometer or hydrometer out, so I just have a little taste.

Does it taste sweet and yeasty?
Yes, then leave a bit longer.
No, get it in the keg then.
Both sound methods...

I've used both on occasions...
Any excuse to sample the beer!

:oops:
It would be nice to know though if there is a definitive answer on using a refractometer Post fermentation...


8)

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jmc
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Re: Refractometer software, WARNING!

Post by jmc » Thu Jan 12, 2012 9:32 pm

Interesting topic.

I use a spreadsheet based on the US MoreBeer.com refractbeer.xls calculations:
http://morebeer.com/public/beer/refractbeer.xls

The one I use is an Excel grid I made, using formulae in refractbeer.xls of all my typical OG & FG.
I wanted to be able to print it off & use it in the garage away from PCs etc. See below:
Image

Formula it uses for OG (eg cell B19) is
=1.000019+0.003865613*(A19)+0.00001296425*(A19*A19)+0.00000005701128*(A19*A19*A19)
Where A19 is cell containing Brix OG

FG calc (eg cell I19, OG 12brix, FG 5brix = 1004)
=(1.001843-0.002318474*($A19)-0.000007775*($A19^2)-0.000000034*($A19^3)+0.00574*(H$9)+0.00003344*(H$9^2)+0.000000086*(H$9^3))+(1.313454-0.132674*Temp_F+0.002057793*(Temp_F^2)-0.000002627634*(Temp_F^3))*0.001

$A19=OG in Brix
H$9 = FG in Brix
Temp_F = temperature , (optional correction factor)

I've used my refractometer and chart for over a year now and have been very happy with it.
For 1st 6 months I checked FG with hydrometer, and it was always accurate to a couple of points.
I rarely bother with hydrometer now.

I do check that FG in keg/bottling range and that its constant for 3 days prior to kegging or bottling

One thing not mentioned so far is affect storage temperature has on the refractometer.
I always calibrate my refractometer (with tap water) before taking a reading.

If temp has changed by 2C or more (since it was last used) I find I need to adjust refractometer (with tiny screwdriver) to set water at 0.

My refractometer is stored in the garage and so its very suceptible to big temperature changes.
For more on this see Topic: Refractometer

** Edited typo in formula **

steve_flack

Re: Refractometer software, WARNING!

Post by steve_flack » Thu Jan 12, 2012 10:41 pm

As another author of home brewing software, I'll put my hand up and say it uses the God awful cubic formula that Promash et al uses. If you don't use it you get people emailing saying "Your app doesn't match app X. It must be wrong."

This thread has made me think though and I've come up with another way to work this out. I'm sure Graham will jump in if I'm talking bollox..

Assumptions

1) If you measure the brix during fermentation then the drop in brix from when you started is due to consumption of relatively simple sugars.
2) Fermentation of those sugars doesn't just remove the gravity due to the sugars it also additionally lowers it due to the lower density of alcohol
3) The fermentation is clean in terms of stoichiometry C12H22O11 + H2O → 4C2H5OH + 4CO2 (an oversimplification).

So if we work out the FG from the brix using the same formula as we use for OG we can simply multiply the difference between that FG and the OG by a factor to get the real FG.

SG from Brix is (from De Clerc)

sg = (brix/(258.6-((brix/258.2)*227.1))+1) You could add a correction to this is you want I guess - 1.04 is popular (so brix=measured brix/1.04)

Then real fg = og - ((og-fg direct from brix)*1.25)

So if you had a starting brix of 10 and finishing brix of 5 (50% real attenuation about 62% apparent attenuation) you would have

OG = 1.038
measured FG = 1.019
Real FG = 1.038 - ((1.038-1.019)*1.25) = 1.012

In case your wondering, 1.25 was chosen to make the numbers fit the real and apparent attenuation figures. It also fit the general idea that one pound of sugar in 5 us gallons adds around 8 points to your gravity but will lower you FG by an additional 2 points (10 points in total)

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gregorach
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Re: Refractometer software, WARNING!

Post by gregorach » Fri Jan 13, 2012 10:26 am

boingy wrote:
gregorach wrote:But what about us data junkies?
Heheh. I would have though as a data junkie you should be using a hydrometer in preference anyway. I'd be tempted by those narrow scale ones that someone linked to a while back (maybe Aleman?). Each one covers a reduced range so it's easier to read small changes. I seem to recall they were also pretty large so they needed a large trial jar and also that they commanded a higher price. (A quick search failed to find the post I'm thinking of...)
Pulling a large enough sample aseptically is difficult to impossible with my current setup.

Those narrow range hydrometers are nice, but they're bloody expensive (about 60 quid each IIRC) and you need half a dozen.
Cheers

Dunc

Graham

Re: Refractometer software, WARNING!

Post by Graham » Fri Jan 13, 2012 1:05 pm

steve_flack wrote:If you don't use it you get people emailing saying "Your app doesn't match app X. It must be wrong."
Yes, that can be a problem if you try to do anything in a different way.
steve_flack wrote: This thread has made me think though and I've come up with another way to work this out. I'm sure Graham will jump in if I'm talking bollox..
It is almost exactly what I do in BeerEngine. I use what I think is called the Lincoln equation to convert to and from s.g. and brix, and I use 1.24 rather than 1.25 for a reason that I do not remember, probably not a valid reason. It could be taken a step further, not that I have, inasmuch as we then know the amount of sugar that has been consumed. Subtract, say, 5% for yeast metabolism and then approximately 50% of what's left will be alcohol by weight. If it matches the official Excise alcohol table then it will be accurate enough. We then have all the information necessary to calculate apparent final gravity to better accuracy than a fixed factor of 1.25 without resorting to messy polynomials.

The major snag here is that there is no compensation for the way alcohol affects the refractometer reading. A refractometer is really only valid for binary solutions; in this case water and sucrose. Other components present in the cocktail being measured may interfere with the sugar reading. I suspect that the amount by which alcohol affects the reading will be determined by the presence of, absence of, or the quality of the sodium-D-line filter in the refractometer. I suspect that cheap refractometers don't even have a filter.

Looking around the web; the people that use the 'usual' refractometer correction calculators and tables differ in their opinion as to their accuracy. About half say the results are spot on; the other half say they are miles out; 8-12 points out. Track down the reason for this discrepancy and we are half way there. However, just looking at the figures given by these formulae it is intuitive that, in many cases, they cannot be right. It is why I think that somewhere along the line, the wrong end of the stick has been grabbed.

I also suspect that many of the refractometers are just plain wrong. People think that they are "calibrating" their refractometers by measuring water, when in fact they are merely zeroing it. The only way to calibrate their refractometer is to make up a standard sugar solution and measure that. Anyone with a half decent electronic gram scale or herb scale can make up a standard sugar solution with good enough accuracy for this purpose. I reckon that some people would be in for a surprise if they did that.

I am sure that this refractometer stuff can be greatly improved, but in the end it is probably true to say that it is an inappropriate instrument for the purpose; a bit trying to cut your hedge with a wood chisel.

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Re: Refractometer software, WARNING!

Post by gregorach » Fri Jan 13, 2012 2:43 pm

Graham wrote:The only way to calibrate their refractometer is to make up a standard sugar solution and measure that. Anyone with a half decent electronic gram scale or herb scale can make up a standard sugar solution with good enough accuracy for this purpose. I reckon that some people would be in for a surprise if they did that.
I have in fact done this with my el-cheapo refractometer - in fact I've done it with 3 different sugar solutions (1.040, 1.020, and 1.010), and checked each against my hydrometer rather than relying on calculating the expected gravity. I found that the SG scale on my refractometer agrees with my hydrometer to within +/- 0.002 (which I regard as the reading accuracy of the hydrometer anyway) across the whole range. However, I didn't check the Brix scale at the time... I have noticed that the correspondence between the Brix and SG scales on my refractometer doesn't agree exactly with the calculations given by any formula I've found so far, but this error is again only around +/- 0.002. I also regularly compare post-fermentation gravity figures (calculated from a Brix reading on the refractometer) with actual hydrometer readings, and again they agree to about the same level of accuracy.

I can't help but suspect that anyone who's finding their refractometer reading is out by 8-12 points is talking about a post-fermentation reading and not correcting for the presence of alcohol. That's exactly the sort of error range you'd expect for an uncorrected reading in a fairly typical (4-5%) beer.
Cheers

Dunc

JohnMarso

Refractometer software, WARNING!

Post by JohnMarso » Thu Feb 23, 2012 2:03 pm

Has anybody used brixcalc on the iphone
Any thoughts

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Re: Refractometer software, WARNING!

Post by Jocky » Fri Feb 24, 2012 11:25 am

There's a post on the first page of this thread by the author of BrixCalc for iPhone:
viewtopic.php?f=6&t=46946#p498453
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mark4newman

Re: Refractometer software, WARNING!

Post by mark4newman » Sat Mar 03, 2012 12:48 pm

Hi

I have just brewed an imperial porter, and thought I would check what was going on. I even purchased an extra hdrometer to make sure this was correct.

Anyway, the IP had on OG 1.080 which read 20 on by refractometer. The internet software said this would be 1.083 and beer engine said 1.080. (The internet software seems to miss the 1.4 adj)

Anyway it finished brewing on Wednesday and I have checked the FG, which is 1.022 and the brix is 11.2. The software comes up with a value of 1.021 and Beer engine comes up with 1.034

oldtimer

Re: Refractometer software, WARNING!

Post by oldtimer » Thu Apr 05, 2012 9:36 pm

I just want to make an observation here.

It just goes to show munch I have got to learn about brewing.
I have only been brewing for about a year and am still on a big learning curve..

I have read this thread right through, and I have got to say, not one word of it made sense to me. I do not know what a beer engine is. I do not know what a refactometer is or what it does. Yet you fellows talk about it so glibly.
So perhapes someone could give me some guidance as to where look/read to educate myself further. I am very keen to learn and ALWAYS willing and eager to speak and hear what those who know have to say. I do have GW'S book.

To date I have compleated about seven or eight brews ( all grain and kit). And so far the beer tastes good to ME, but having said that, I want to improve.
So any help I can get would be well appreciated. :?: :?:

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Re: Refractometer software, WARNING!

Post by orlando » Thu Apr 05, 2012 9:53 pm

A primer on Refractometers http://en.wikipedia.org/wiki/Refractometer

A link to Beer Engine (It's brewing software devoloped by GW and contains calculators and brewing tools such as adjusting hydrometers for higher temp readings and converting refractometer Brix readings into OG readings. http://www.practicalbrewing.co.uk/calcu ... eerengine/
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Fermenting: Blitzkrieg Hop
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Drinking: India (real IPA), Kernel Bogey (Reprise), Autumn Almanac
Up Next: Peaches (Peach IPA), Party Like A Russian (RIS), Black Night
Planning: Autumn drinking beer.

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Re: Refractometer software, WARNING!

Post by orlando » Sat Apr 14, 2012 4:21 pm

I've done a little more poking around the subject of refractometers and made a discovery that now means my hydrometer and refractometer now tally when measuring the same wort, even if that is there both wrong. I started by checking both of them for water with the hydrometer, it did read 1.000 and distilled water with the refractometer and it too read 1.000. I haven't yet calibrated them in different sugar solutions but want to run this past the experts first. I took a look at Graham's Beer Engine and read through the specific notes concerning refractometers and discovered that the correction factor needs to be adjusted for your kit. I used my hydrometer and refractometer on a brew this week and measured the same wort at 20c (both devices calibrated for that temp) and took the readings from both ( 1.040 & 9.4 Brix) I then tried to adjust the correction factor in Beer Engine but it didn't seem to want to play. I then went to BeerSmith2 and did the same thing in their hydrometer section and found the correction should have been .94363 and not the 1.40 that Beer Engine had as the default. Once I did this I went back to Beer Engine and to my surprise it had now changed the correction factor to the same amount. My hydrometer and refractometer now agree. Phew. This was all done with unfermented wort by the way as I am aware of the problems with yeast and alcohol and I am also aware of how different worts will have different quantities of maltose and dextrins to further complicate things but other than these couple of caveats is there anything else you guys think I might have missed?
I am "The Little Red Brooster"

Fermenting: Blitzkrieg Hop
Conditioning: St. Petersburg (RIS)
Drinking: India (real IPA), Kernel Bogey (Reprise), Autumn Almanac
Up Next: Peaches (Peach IPA), Party Like A Russian (RIS), Black Night
Planning: Autumn drinking beer.

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Re: Refractometer software, WARNING!

Post by yojimbo » Sat Apr 14, 2012 8:19 pm

Been brewing today and tinkering at the same time i made up 3 sugar solutions got them to 20 c and measured them with hydrometer then the refractometer they tally up spot on found formula to convert gravity to brix for sucrose on wiki . Going to have a look at the correction factor on beer engine brew went well got og of 1.063 brix reading was 15.6 I convert the 1.063 og to a brix value of 15.42 . I presume the differance bettween the two brix values must be the correction factor ?


Not used the refractometer once fermentation has started but have noticed its out compared to the hydrometer but not by much fot the og.
Did yer like that?

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