Refractometer

[Leyther]

Nope that's the one I should be getting delivered today. Can you get distilled water from Woolies?

You can get it from Coles so I expect you can also get from woolies

Beware there is distilled and demineralised, they are different, you want distilled.

 

[Lowlyf]

You can get it from Coles so I expect you can also get from woolies

Beware there is distilled and demineralised, they are different, you want distilled.

Right thanks lads

 

[Lyrebird_Cycles]

Technically, I think you need to use sunlight, but a knowledgeable friend of mine said that using the same light will give you a consistent scale, and the difference will be miniscule.

View attachment 106522

Technically you need to use the D line @ 589 nm from a sodium vapour lamp. A yellow LED with a lambda max around 590 nm is the next best thing.
If you use a polychromatic light source the division blurs somewhat due to the spread of refactive index with wavelength so you lose precision but preserve accuracy.

 

[Lyrebird_Cycles]

Can you get distilled water from Woolies?

The 10 l bag in a box of "Pureau" is as good as anything and very cheap. It's what we use in the lab at the winery.

 

[Matplat]

I get 4l of reverse osmosis water at a time (from one of those self serve water machines) to make up my starsan. Would this also be suitable?

How much difference will the water actually make? Are we talking 0.1 Brix or more like 2-3 Brix? I realise that's a slightly open ended question, but within reason if you know what I mean...

 

[Lyrebird_Cycles]

Three tenths of the square root of FA.

Taking Melbourne water as an example of a good water supply, typically the tap water is around 100 uS/cm: my tap this morning read 107.

If this were all sodium chloride* that would be about 50 ppm NaCl, that's 0.005%. Your refractometer would read that as about 0.006** Brix. This is within the error band of even a lab grade refractometer with a monochromatic light source.

Taking Adelaide as an example of a bad water supply, the conductivity of the water can be around 400 uS/cm, so multiply the above figures by four. The error is still only about 0.025 Brix.


*which it isn't but the other likely components are in the same order of magnitude for refractive index vs concentration.

** Because the relationship between concentration and refractive index changes with the solute. At the same concentration, sucrose will read about 20% higher than sodium chloride on a refactometer.

 

[MitchD]

So what you are saying is that for the average brewer tap water is suitable for calibration?

 

[Bribie G]

I'll sell you a litre of my tank water, will last for ever.

 

[Lionman]

I use one that reads in Brix only.

Its not as accurate as a hydro, but I never use my hydro now. I dont need precision.

Its easier to use and wastes less and the temp doesn't matter.

There are calcs available to convert the readings in to SG pre and post fermentation. The readings seem to line up with my recipes pretty much all the time.

 

[Lionman]

How do you calibrate a refractometer??

You put water on it and dial it in to a 0 reading. Distilled water is probably best but tap water will be fine in reality.

You are meant to also calculate your devices 'Wort Correct Factor'. This is because refractometers are designed to measure sugar in water, not sugar in wort. The other stuff in wort other than sugar will impact on the reading. Brewers friend has info on it. I find the impact is so small it has bugger all impact really, at most a few percent, so I dont bother.

When you take readings, it pays to take a few with different samples, as you can get misreads as the sample size is so small.

 

[Lyrebird_Cycles]

refractometers are designed to measure sugar in water, not sugar in wort. The other stuff in wort other than sugar will impact on the reading.

As far as I can work out it's mostly the types of sugars present which affects the reading. As an example a pure solution of maltose will read almost 7% high on a refractometer designed for sucrose.

 

[Sidney Harbour-Bridge]

Wouldn't you use the same water as you use for mash/sparging to calibrate?