Refractometer

[Brew_DD2]

https://www.stevenson-reeves.co.uk/reeves/HPKM.htmI use a 1.005-15 for FG and 1.030-60 for OG. The FG one is certified, (and expensive)

I'd bloody love an FG hydrometer. Anyone make any suggestions of where to get one that won't require me to remortgage my house?

 

[peebee]

I'd bloody love an FG hydrometer. Anyone make any suggestions of where to get one that won't require me to remortgage my house?

Forget hydrometers! Use a pyknometer, they are just bottles with a hole in the stopper. Cost next to nothing but you will need descent weighing scales to weigh accurately to ... I think it was +/- 0.012g for a 25ml bottle (25ml is the sample size). You can get digital balances that have okay stabilising algorithms for £30-50 or you can use not so good balances for 50ml bottles (or pay £80-120+ for some really smart balances). No fine lines to read, no distorting meniscus. It will need some simple maths (a calculator) including converting from density (g/ml) to relative density (SG) which is divide by 0.9982 for a 20°C water reference like brewing hydrometers will (should) be using (the gravity "SG" is relative to).

Yeah, fiddly accuracy, but SG is a measurement of 1ml in grams to 3 decimal places, relative to 1ml of pure water (which weighs in at 0.9982gms at 20°C).

 

[StJayJay]

Just to nudge back to the original question when I resurrected this thread (although I’m genuinely enjoying all the other refractometer information, very helpful )
Does dissolved co2 in a sample have any affect on a hydrometer reading?
I know the physics behind the affect of dissolved gas on hydrometer readings with buoyancy and relative densities etc.
I’m much less clear on refraction and whether dissolved gasses affect refraction and wonder if any one else knows about this?
(I suppose I can get another sample and degass it to see if that does anything, I’m just being tight/lazy in not wanting to take another sample!)

 

[Agentgonzo]

This page says "One volume means 1 L of CO2 in 1 L of drink. This is equivalent to 1.96 g/L (normally quoted as 2 g/L). ".
So let's pick 3 volumes as a well carbonated beer. That's 6g/L.

I'm having trouble finding any resources that I can understand that tell me the relationship of dissolved CO2 affects the refractive index (which leads me to think that it doesn't have much effect at all, but I could very well be wrong in this).

But let's for the sake of argument imagine that we instead dissolved 6g of sugar in a litre of water (wort) instead of CO2. 6g/L equates (using this calculator) to a SG of 1.00236.

So in summary, I would say that it affects it a pretty small amount, and so not something to be overly concerned about.

One thing I know for certain is that if you have a carbonated liquid, when you put it on the refractometer, it'll bubble somewhat, making it harder to read and the result being less accurate

 

[Agentgonzo]

Sodastream to the rescue (for science!).

I filled up the soda stream bottle with 20 degrees filtered water, and then used this to calibrate the refractometer to exactly zero. Took multiple reading to be sure. All read 0.0 Brix.

Then I carbed up the bottle in the soda stream (my standard '1 fart fill, then leave for 30s whilst faffing around and finding my glass/ice - but this isn't really the important variable here) and measure that on the refractometer.

1. Yes, it is definitely harder to read. Whilst the water can go onto the refractometer without many bubbles, as soon as you close the lid, the bottom of the transparent 'lid' on the refractometer causes lots more nucleation sites than the glass side, and it quickly filled with tiny bubbles, blurring the reading more and more making it hard to read.
2. You need to be pretty quick at reading it due to the above
3. I took multiple readings to be sure (again, for science)
4. I was trying to take photos to post, but a combination of the dexterity needed to hold the phone up to the lens, put the water on it and do all of this before it bubbled up weren't possible for me.
5. To the best of my ability to read the readings quickly (which I'm fairly confident of with multiple readings), the carbonated water also read 0.0 brix. If you pushed me, I would say there is a slight possibility it was reading -0.1 (the smallest I can honestly see on the refractomer), but this is well within the error margin as the water fizzed and the reading blurred out (I would say the error margin started at 0.2 brix and and then went up from there quickly over the following seconds to above 10 brix).

 

[Agentgonzo]

They are also calibrated for fructose/sucrose, which means you need to apply a "wort correction factor". Mine (0.9) seems to be deferment from values on the internet .

I have never seen a correction factor that high - ( low) - 1.04 seems typical

I probably should have done this a while ago, but I made up some sucrose solution today to calibrate the refractometer (and actually see how accurate my hydrometer is - up until now I've just trusted it).

I measured the SG/Brix of distilled water (condenser dryers are a great source of distilled water in the home - I use this when making up starsan solution!) using both the hydrometer and the refractometer.

• Refractometer (calibrated): 0.0 brix = 1.000 SG
• Hydrometer: 1.001 SG (close enough)

I then made up 13.0g of sucrose in 100g of distilled water at 20C (100ml). Giving me 130g/L, which this calculator tells me should be an SG of 1.04997, or 1.050 to us mortals.

I remeasured the SG of the sucrose solution:

• Refractometer: 11.4 brix = 1.045 SG
• Hydrometer: 1.050 SG

So it's my Refractometer that's out of whack (and the above agrees completely with my 0.9 conversion factor I need to apply for my refractometer).
Yes, it was a cheapish one from Amazon.

As I said, I just know how to convert my refractometer, and only use it for rough readings during fermentation to see whether it's complete, so it's good enough for me. Interesting though. I wonder why it's so far out (it's a shame all I can do is calibrate the zero point and not the scale of the readings).

 

[StJayJay]

Sodastream to the rescue (for science!).

I filled up the soda stream bottle with 20 degrees filtered water, and then used this to calibrate the refractometer to exactly zero. Took multiple reading to be sure. All read 0.0 Brix.

Then I carbed up the bottle in the soda stream (my standard '1 fart fill, then leave for 30s whilst faffing around and finding my glass/ice - but this isn't really the important variable here) and measure that on the refractometer.

1. Yes, it is definitely harder to read. Whilst the water can go onto the refractometer without many bubbles, as soon as you close the lid, the bottom of the transparent 'lid' on the refractometer causes lots more nucleation sites than the glass side, and it quickly filled with tiny bubbles, blurring the reading more and more making it hard to read.
2. You need to be pretty quick at reading it due to the above
3. I took multiple readings to be sure (again, for science)
4. I was trying to take photos to post, but a combination of the dexterity needed to hold the phone up to the lens, put the water on it and do all of this before it bubbled up weren't possible for me.
5. To the best of my ability to read the readings quickly (which I'm fairly confident of with multiple readings), the carbonated water also read 0.0 brix. If you pushed me, I would say there is a slight possibility it was reading -0.1 (the smallest I can honestly see on the refractomer), but this is well within the error margin as the water fizzed and the reading blurred out (I would say the error margin started at 0.2 brix and and then went up from there quickly over the following seconds to above 10 brix).

Thanks for the experiment there, great idea using the soda stream. With the beer I was making, I’d had a week of readings that hadn’t nudged from 9.6 brix. It was only when I randomly put some on a sample I’d drawn to test carbing level it had dropped to 9.0. I suspect id just done something in my handling of the keg/slight temp rise to eek a bit more life from the yeast.
I couldn’t think of a reason why carbing would have a major affect but I’m glad you were able to confirm, appreciate your efforts!