Refractometer?

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stux wrote:You need to know your OG in order to use a conversion tool/table to convert the final reading to final gravity.

The alcohol interferes with the reading and by knowing the OG you can compensate

what he said

i use a refractometer exclusively. I love it. i measure my gravity during the mash and boil several time and can adjust boil time or water volume to accurately hit my planned OG. when using the refrac to measure FG of fermented beer you must use a correction tool. i recommend this read:
http://seanterrill.com/2011/04/07/refra" onclick="window.open(this.href);return false; ... g-results/
and i use his spreadsheet to track my brews.

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Just a word of warning daddyo from a refractometer non-enthusiast .

A search of refactometer and PistolPatch will show why I'm not into refractometers. (I personally think they are meant for getting the average sugar level in a field of grapes. ) Maybe I just have a dodgy one but I've found my readings pretty unreliable over the years getting only occasional agreement with a hydro. In fact, now my refractometer isn't even close even though it reads fine at zero.

Anyway, ignore my opinion especially as refractometers are so cheap these days. Also, many other brewers think they are great. Just remember, like any instrument, to check it occasionally at least, in this case, against your hydro. A single speck can throw a funny reading so just be careful.

Have fun though ! The one you linked should be as good as anything else I imagine.


PP

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PistolPatch wrote:Just a word of warning daddyo from a refractometer non-enthusiast .


The one you linked should be as good as anything else I imagine.


PP

Wow, a ringing endorsement from PP!

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[MODNOTE: This post and several subsequent posts were moved to this older thread as the title is better and the information below can be more easily found. For ease of reading, I have deleted one sentence in the old thread and the two sentences that originally began this post...]

I bought one of the first refractometers close to when they were marketed as being able to be used for beer. Do a Google search for refractomer and wort and you won't find anything before 2003. Refractometers are used for such things as measuring sugar in urine and plasma, salinity in aquariums and the opacity of gemstones. In viticulture, they have been used in the last twenty years or so on some vineyards to measure the sugar content of ripening grapes in a vineyard. Many grapes are sampled though.

All the above, with the exception of viticulture, rely on a very consistent medium to give an accurate result. Viticulture does not rely on refractometers and wort is a lot less clear than grape juice. I'm probably one of very few people in the world that have tested hydrometers versus refractometers side by side. I have written on this before many times quite a few years ago. If my memory serves me correctly, the problems with a refractometer (and often with a hydrometer) were...

1. Reading would change significantly over a short period of time. (Refractometer only.)
2. Reading would change from one sample to the next even if taken at the same time. (Mainly refractometer but also sometimes on hydrometer.)
3. Reader error: I have often given the same sample to several brewers and asked them to write down the measurement and they have all disagreed. This somewhat ties into 1 above but I think it goes far deeper deeper...

Personally, on the same wort, I think you can get a very wide range of readings from a refractometer depending on how you sample that wort. Basically, you can get whatever reading you want either by accident or justification. For example...

On hot readings, basic physics tells us that if you take a teaspoon of hot wort and let it cool down, there will be a lot of evaporation making the wort appear stronger than it actually is if you wait for it to cool. That is a fact and there is no arguing with that. Follow the procedure in the link at the end of this post and that is not possible.

Secondly, on a tiny sample such as two or three drops of wort, basic physics of refraction tells us that even a small particle (but usually much bigger), will greatly affect the reading. That, again, is a fact and there is no arguing with that. It can also be an issue if you take large but crappy hydrometer readings.

Stratification is also an issue and is far more likely to occur with a refractometer reading than a hydrometer reading.

There's lots more to write on this but I'm pretty sure it has already been written on this site if someone can find it .

Here is one post to get you started pilch. Also please study this one.

Better race,
PP

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PP, I was in Industry in the Late 80's, and needed to check the Amount of water vs Ethyl Glycol in machines that needed fire resistant hydraulics, and would not freeze overnight.
Due to the 85C operating temperature, and 18 machines, the only tool usable was refractometer.

A drop or Two is All you need, and 3 measurements will give you a good Average of the Specific Density, of anything mixed with water.

You need to Cool the Hydrometer Sample to 60F or 68F, and need to have the Hydrometer made for that ONE temperature.

If your a Scientist a Hydrometer is the absolute Best tool for Sugar measurements.

I make Beer and Wine, So, Close to a Projected S.G. is Good Enough, I'll use a refractometer.

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Next up we'll recommend that everybody install a tap on their brew kettle, just to see what kind of rise we get out of PP.

J/K Patch, we love you and appreciate the hard work and passion you have invested here.

---Todd

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thughes wrote:Next up we'll recommend that everybody install a tap on their brew kettle, just to see what kind of rise we get out of PP.

J/K Patch, we love you and appreciate the hard work and passion you have invested here.

---Todd

Todd. Very good

Josh, please have another read of my last post in this thread. Slow down bro . I'm not saying refractometers don't have a place and I did list some of the excellent places where they can be properly used. Your example gives another proper and excellent use for them I never knew about. I think though that you missed my major point in that if the original liquid being measured is not clear and not of the right temperature, all sorts of things can go wrong.

If we acknowledge this, then correction tables etc for refractometers/fermenting wort etc become a moot point. In fact, all they do is further muddy the waters. The main thing though is...

If you conduct your brew day correctly, there is actually no need for instantaneous gravity readings or to even waste any wort when using a hydrometer.


[center]How to Test a Refractomer Properly[/center]
Here's what anyone with a hydrometer and refractometer can easily start to test...

A1. Start with your warm urine in a hydrometer jar. You already know the approximate temperature - 37 C / 99F
A2. Measure the specific gravity with hydrometer. (Use time of day when urine is likely to be most yellow).

B1. After taking the above and asap, use an eye dropper to take a few drops of urine from the hydrometer jar and take a reading with the refractometer using that very small sample.
B2. Now fill the eye dropper with urine from the hydrometer jar and then take a reading with the refractometer using that larger sample.
B3. Pour some of the still warm urine from the hydrometer jar onto two teaspoons.
B4. ASAP, take a refractometer reading using the urine from one of the teaspoons.
B5. Allow the other teaspoon to cool and then take a refractometer reading using that sample.

Use the right-hand side of the second sheet of BIABacus PR 1.3T ('Miscellaneous' and 'Hydrometer Temperature Calibration') to correct the specific gravities of all the readings you take.

The above is the most primitive and easiest of hydrometer versus refractomer experiments. There are two other aspects (that I can think of at least) that the above experiment does not test.

Anyone here want to have a crack at this first one? I'll give it a go for sure and we'd want another four, preferably nine to take part.

I would not, however, suggest drinking the hydrometer sample after taking your readings on this particular experiment.


PP

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PP, I have made some pretty bad beer, but, It was nothing like Pee..

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Josh.

Hold on, I don't see you, or anyone else putting their hand up for this test so I'm assuming you now all agree with me .

If you did do this simple test with he refractometer only and not even bothering with the hydrometer, you will definitely come across the first problem with refractometers in that the result you will get depends on the sampling method you use and this is on a clear liquid at a lower temp than hot wort!!!

Mad_Scientist mentioned Sean Terrill's work on getting a refractometer to agree with a hydro using a wort correction factor. If you study that work it is proof that, on top of the sampling problem, refractometers not only have to be given a correction factor for wort but also for different types of wort (have fun with that!). Refractometers are designed to measure the refractive index of light going through a simple sugar in water solution which wort is not.

A hydrometer is by far the most reliable method of measuring wort and even with that you should take a few gravity samples to ensure confirmation.

Let's move onto ball-valves now .
PP

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PistolPatch, I found My refractometer to be Dead On with a temperature Corrected Hydrometer.

One, thing I found is My refractometer needs the SUN, or an Incandescent light source to work well.

Florescent or CFL Lights do not Cut it, and LED lighting is Nearly Useless.

Maybe your refractometer, is Picky about which Light it likes.

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The table above works out specific gravities with no alcohol e.g. original gravity. If the calculator of Sean Terrills you are using is the one I think, it is calculating specific gravity of fermented wort i.e. final gravity only.

The 1.04 correction factor is also just a generalisation. That figure is the first one you need to determine for your refractometer. To determine this, Brewer's Friend, for example, advises here to take, "... at least 30 samples from several different unfermented worts." In another place, it says, "Cheap refractometers are not very consistent measurement to measurement from the same wort. I take 5+ measurements then average the value before recording."

Now, what I meant earlier, by needing to have a wort correction factor for each different type of wort, is that the average of the 30 samples on different unfermented worts is just that - an average. In theory though, you would need to use a different wort correction factor for each wort of different gravity*.

I think if we understand the limitations above, then it helps us use a refracto sensibly. Once you have some experience brewing and taking measurements, then it's normal to become lazy and there's nothing wrong with that. Using a refracto might be easier for some brewers. If you understand the limitations, if you were meant to end up with an OG of 1.050 and your refracto said 1.060, you are going to have the sense to do a second check, with a hydrometer, before you go diluting. In other words, you'll make sensible decisions.


PP

* I never hear reference to this anywhere but I think different coloured worts of the same gravity are also going to give different results. I might buy some food colouring and suss that out later.

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mally wrote:BTW Pat - it gives you pre & post fermentation gravity values.

Good on me - skimming instead of reading!

Okay, what I said in the last post about a WCF being an average still applies, but I'm now seeing what MS was really asking (sorry mate!)...

The reason for the two different readings is because they are not using the same formula [EDIT: And, one of them is wrong!]

[center]Kai's Table[/center]
Kai's table assumes your refractometer works in Brix so it does the following....

Brix to Plato

Normally, 1 Brix = 1.000034 Plato

With a Wort Correction Factor of 1.04 though, 1 Brix = 1.000034*1.04 = 1.04003536

So, if your refractometer measures Brix, then 15.4 * 1.04003536 = 16.01654 Plato

Plato to Gravity

Plato is often 'loosely' converted to SG by multiplying the plato by four and then dividing by 1000 and adding 1 (e.g. 16.02 * 4 = 64.08 then do the other maths and you get 1.0641. The proper formula though is as follows...

SG = 1+Plato/(258.6-0.879*Plato)
eg 1+16.01654/(258.6-.879*16.01654)= 1.0655

[center]Sean Terrill's Calculator[/center]
Reading... reading... reading... reading...

Okay, his calculator is incorrect for OG (at least). What he is doing is applying his 'maths' to the SG as well. In other words, he is dividing by his 'new cubic'. For example, 1.0655/1.0045=1.0607 (see file for the workings.)

Incorrect fg_calculator_v3.0 -PP.xls

[center]The Lesson to Learn (Yet Again )[/center]
Once again, this is an example of something we often find on the net or that gets quoted and it's just not right. It then takes so much time for other people to clean up. (When I say, 'other people,' I'm not too sure there are many actual 'cleaners' around?)

You'll notice on his calculator page, that questions asked weren't answered properly, and no questions have been answered for several years. This is always an interesting sign.

...

I noticed the other day, posts by a brewer who spruiks his BIAB calculator everywhere, intimates it has BIABrewer's approval and is based on The BIABacus, intimates he is in contact with Pat and trashes BIABrewer.info at all opportunities. You'll find him in this thread, just one example of many. His calculator is appalling but, I for one, was very nice to the guy (I am a major idiot ).

[Love the bit he wrote about deleting posts/threads. I know a drunken mod accidentally deleted a thread a few days ago , but he saved all the posts and it wasn't a major drama; I don't care and I had written in that thread. Last time before that I can remember was ages ago and would have, without doubt, been because someone was aggressive (maybe me? ).]

I think I'm pretty generous with my time. Some days though it gets very frustrating to see stuff like what that guy posts. He gets to do a litter of posts all over the net while I get to spend several hours or more just writing one or two. These hours are, more often than not, spent clearing waters that were muddied elsewhere. The above post is just one example.

Anyway, that's my gripe for the month
PP

P.S. I think one of the above formulas is appearing as a Skype number. Microsoft has turned Skype into a bloody virus!!!

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I appreciate your time spent on that Pat.
I downloaded the incorrect fg calculator in the hope I would get a "fast answer" No chance there!

So what I can work out is that, Kai will give you a slightly inaccurate S.G.
Sean Terrill will give you a more inaccurate S.G. but you will be able to get an F.G.

What is "spruiks" BTW? I like the sound of that!
You should get active on the HBT BIAB thread. That would keep you entertained for years!

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