Legitimacy of refractometers and hydrometers?

[MattGuk]

Sounds silly I know, but anybody ever question it?
I wonder if its worth purchasing a precision hydrometer as my readings

never really change much between pre and post boil.
Attached are some photos of a brew I done this evening, with a 2-3 point difference between pre and post boil gravities, even though my volumes were 30 pre boil and 25 post boil.

Pre boil= 30lt @ 1.052-53
Post boil= 25lt @ 1.055-56.

 

[RoomWithABrew]

Temperature corrected ?

 

[foxbat]

Temperature corrected ?

For both the gravity and volume numbers.

 

[Sadfield]

Is it boiling or simmering? Boil length?

Is the 25L post boil volume measured in the fermenter and include kettle losses?

 

[MattGuk]

Yep, all measurements are @20°c.
Electric brewing, strong boil for an hour with volumes reduced by 5ltr in that hour.
Maybe brewfather is over estimating my number, however when I put all the relevant into a calculator like brewers friend boil off calculator, says I should be at about 1.064 with these volumes

 

[Sadfield]

Could be wort stratification, where the solids in the wort sink to the bottom and you take a sample from the top, or the other way, heavier wort from the bottom depending on which sample is giving the erroneous reading. In my experience the preboil can be the one that stratifies easiest. Did you mix the wort before taking each sample?

 

[MattGuk]

Yeah, the samples were all mixed thoroughly, long whirlpool during cooling, plus I swirled the fermenter a lot before taking the reading, it's really baffling me how on every batch I only ever see a slightly increase in gravity between pre and post boil gravities, even though the volume has been reduced by a fair amount.
I did leave the sample overnight, and that is currently reading about 1.058-60, but that is at about 10°c.

 

[The Baron]

I personally do not generally bother with pre-boil measurements and only take a OG. I find it does not really matter to me as long as my OG is roughly where it should be according to my recipe forecast
I know some brewers like to be spot on with every sector but I just enjoy my brewdays and cut out anything that can stress the day as its what goes in the FV that matters to me nand whether its down to experience I am nearly always there or there abouts
Ps I do do PH though but again I seem to get that right most times maybe its because I know my system through time and usage
Wow in danger of sounding like I know what I am doing?

 

[Sadfield]

Yeah, the samples were all mixed thoroughly, long whirlpool during cooling, plus I swirled the fermenter a lot before taking the reading

How are you measuring the two volumes, are they accurate? Don't trust what they print on buckets.

 

[MattGuk]

To be honest I go by the measurement on the FV plus on the brewmonk, they match up perfectly.
I did measure my water amounts when I first got the brew monk by pouring a liter at a time and weighing to to make sure I had a weight of 1kg per ltr of water ( after setting the scale with an empty jug ) and they matched up perfectly with the brew monks markings, which incidentally matches up to the FV pretty much.
Maybe I should not be so hung up on gravity difference pre and post boil, but it would be nice see I hit all number lol

 

[The Baron]

Just focus on the OG to FV thats what I do Matt it makes the day a little easier and if I am down a couple of points and I really wanted to be spot on I add a little sugar to boost it up but usually I am within a couple of points and do not bother .
Its not a bad thing to chase the numbers for brewing experience but as your beers are good it becomes less of a thing that may matter to some brewers

 

[gyurmaember]

I feel the stones coming at me, at the last brew I didn't bother to take out the refractometer, my hydrometer is resting in it's box since I confirmed my tilts are 3 points off when alcohol present (and spot on when not present). Good enough for me.

 

[MattGuk]

I never used to check pre boil gravity, however, since using brewfather I thought it's a good reference point to see how the brew is progressing and to see if my hopping might have to change due to lower or higher than expected gravity.
I shouldn't get to hung up on it I guess, this was the smoothest brew I had in AGES, and my efficiency was much higher than the normal ( probably due to sparging instead of full volume mashing ) 65%.
Instead of an ESB I might and up with an EESB lol

 

[Galena]

I always check pre-boil gravity with a refractometer as it gives you an idea of whether you may need to boil any extra off or add any dme. I also do a refractometer check with 15 minutes to go to confirm I'm on target or thereabouts, the OG as it goes into the FV is clearly the important one.

 

[foxbat]

I always check pre-boil gravity for the same reason as @Galena. I know how many points I'll gain during the boil because it never changes and so I can pre-empt a missed OG with the addition of brewing sugar or water.

 

[hoppyscotty]

In my mind pre-boil gravity is the most important as it gives you a measure of how good your mash efficiency is. The post boil is just a measure of your boil off rate.

I would have thought that a discrepancy of a couple of gravity points is good isn't it? How accurate does it have to be? Refractometers are not the best tool for the job anyway and you should really calibrate them against a trusted Hydrometer - there is a video on YouTube on how to do this and how to enter a correction factor into Brewfather as refractometers are really designed for measuring sugar levels of fruit juice and not wort so can be a few points difference.

 

[Clint]

I only use a cheap hydrometer I've had for years. I do check OG and FG . As long as the OG is something like I'm aiming for with the numbers I used then I'm fine with it.

 

[RoomWithABrew]

agreed @hoppyscotty mash efficiency the variable to control ( or less in control / more variable) but brew to brew aim for consistency / improvement.
This video is good to watch not sure if it's the one you refer to.

 

[hoppyscotty]

That's the one @RoomWithABrew. Keep meaning to calibrate mine but never seem to get around to it.