Who wrote the grumpy post above?
. Come on fellow brewers, I was just trying to take the piss out of you. (Oh no, this thread is not only bringing the coarseness out of me but also the poorest puns
Anyway, you lazy buggers, here's my results...
[center]Refractometer versus Hydrometer Tests
I tested the following samples; plain tap water, urine, urine/sugar/coffee mix, sugar/coffee mix and a sugar/water mix. Here's a pic of one of the tests. Before downloading the spreadsheet, what test do you think it is? (You'll be wrong
You can download this spreadsheet for the results. The spreadsheet makes the results look a lot easier than they were to take. I had the usual sample problems, for example taking two samples, after mixing, from the same large sample, and getting two different results, as well as "creep" (explained below).
One thing I learned that I hadn't really put much thought into before due to the countless problems I've had in the past measuring actual wort, was the temperature aspect of refractos. Most of us know that if we take a hydrometer sample, we need to adjust the reading back to the temp the hydrometer is calibrated at (usually 15 C or 20 C). But, if you are taking a refractomer sample of say hot wort (which you shouldn't do), what temperature should you make the adjustment from? It might seem obvious to me now, but it wasn't before - use the temperature of your refractometer i.e. whatever the ambient temperature is. For example, it's relatively hot here so ambient temperature and therefore the temp of the body of my refracto ranged from 29 C to 26 C throughout the duration of this test.
Btw, my hydrometers and refracto asssume a temperature of 20 C. I have several hydrometers but the two I used are my most trusted ones. Note, however, that they still have about a 1 point discrepancy between the two.
On the tests marked *** and ****, to mimic darker worts, I used instant coffee (forgot to buy food colouring again!). The latter of these was much darker than the first.
1. As mentioned above, problems getting agreement from two identical samples on some of the tests (Tests * and *** for example).
2. "Creep" on one of the two tests where I actually looked for creep. By creep, I mean reading the refractometer sample, letting it sit for ten minutes, and then reading it again only to find the measurement has risen. Creep occurred on Test ** but no creep from Test ****/*****. (Also see next point).
3. Basically impossible to get a reading on the darkest coffee test which had the colour of a Schwartzbier. There was basically just a gradual blur from white to blue looking through the refractometer. In my results, I said 11.2 to 14.2 but I changed the 11.2 from 10.2, thinking I must have read the refracto wrong.
4. Very clear view through the refracto on the sugar/water mix. In fact, that is the pic above. I used raw, not white, sugar - about 8 heaped teaspoons in a coffee mug. Urine was darker.
Before Readiing the Conclusions
1. The above tests were done on solutions of far less complexity than wort.
2. The above tests were done on ambient to warm solutions. A far higher degree of error would result if the above solutions were heated to mash or boiling temps.
3. This is one set of tests, from one person.
4. Only one refractometer and two hydrometers were used in the tests (on some tests only one hydrometer).
The first conclusion is that these tests are as simple as you will ever get. The above tests are much easier than measuring ambient wort, let alone hot wort or beer.
As mentioned above, the refractomer readings, except for plain water and the sugar/water mix, were difficult to arrive at. (Two samples reading differently even though taken from the same, well-mixed larger sample and "creep" are two examples.)
Even given the limited number of tests done above, it wouldn't be unreasonable to hypothesise that the darker the sample, the more unreliable the refractometer reading, assuming you can even get a reading.
The only tests where the refractometer and one of the hydrometers came close were on plain water where the refracto and Hydrometer 1 matched, and on the second urine test where Hydrometer 2 came very close to the refractometer.
When I first started all-graining, I could never understand why a mash brewer would use a "traditional" paddle. It was unheard of at the time, but on my first mash, I bought the paint stirrer/potato masher that is becoming more widespread each year (I'm actually very proud of that
). Similiarly, whilst I'm pretty sure I do know where refractometers started in beer brewing (an Australian retailer), once I got past my excitement at the purchase and started really testing my refractometer out, I really questioned if they have any real place in brewing. Every time I examine the issue in detail, and I've done it many times now, the more certain I am that it is an unnecessary purchase, a purchase that can even often obstruct learning.
On top of all that, a hydrometer on a brew day and during fermentation, can far more easily and accurately do anything a refractometer can, for the same amount of wort.
I've said before, that refractometers are great if you are making wine; you go into the field, squeeze grape juice (always light coloured) onto your refractometer, take a reading and then walk to another part of the vineyyard and take another grape. The winemaker repeats the process many times, and, the average of those samples, gives him/her a very good idea of the sugar content of the entire vineyard.
But, for beer brewing??? I'm sorry but I really don't think so.
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