Instruct Me In Refractometer Usage

[Fat Bastard]

But I'm buggered if I know what.

I keep getting weird readings. When I take samples from the mash, and boil, the readings are consistantly lower than they should be. Both times I've brewed (BIAB), the post boil reading has climbed to after my wort sample (in a glass) has rested for an hour while I clean up.


The first brew I did was a big IPA, and the sample I took immediately post boil was cooled in the bulb of the pipette in a glass of ambient temperature water. The first reading was spot on target (1.068) I reserved a bit of the bitter wort for sampling purposes and retested. The reading off the refrac had climbed to 1.080 and was 1.078 off the hydrometer (which makes sense, it reads .002 low in water). The sample I took after 24 hours in the FV was 1.074 off the hydro, and has consistantly dropped since and is now sitting at 1.028 (a bit high, hoping it drops a bit before I bottle on the weekend!)

Similar story from Sunday's brewday. (SMASH using Maris Otter and Nelson Sauvin) Missed my target on the sample taken immediately post boil, but was within .002 after the wort had been resting for a while. I'm yet to take a sample from the FV.

I'm reading off the SG scale on the refrac. I know this isn't the ideal way to get the "true" SG, but should be ok for comparative purposes, and correlates with the hydrometer.

The refrac has been calibrated with RO water, and I cool the sample thus:

One thing I did notice was that after cooling, there is a bit of break material in the bulb of the pippete, which of course gets onto the prism of the refrac. This has settled out of the sample of leftover wort by the time I get around to testing it after cleanup. Could this be effecting my readings? Should I be taking a larger sample and allowing the break to settle before trying to take a refrac?

I must be doing something wrong. I can't see what though. Probably obvious to an old hand!

Cheers,

FB.

 

[fcmcg]

The sample I took after 24 hours in the FV was 1.074 off the hydro, and has consistantly dropped since and is now sitting at 1.028 (a bit high, hoping it drops a bit before I bottle on the weekend!)

Mate,
Not sure about your refractometer , as i am having some problems with mine as well .
However , i just wanted to say , you don't have to set this weekend in stone to bottle....if it's not ready to bottle , it's not ready...
Better to get 3 days of the same reading before you bottle..and not have bottle bombs...
As for your refractometer....i've taken reading post boil ( cooled sample) and had a completely different reading 4 days later when i've dumped the no-chill cube into a fermentor....no idea why..same as you..calibtaed with distilled water....
Let's hope one of the guru's gives us an answer....
Cheers
Ferg

 

[6tri6ple6]

do you use a hydro/temp calculator to calculate a true reading?
Heres what i do, when i take a sample of wort from my kettle i fill a test tube and let it sit on the bench until im ready to measure it. I drop a digital thermometer into it as well. I usually leave it around 1/2 hour or so and all the trub has sunk to the bottom. I then take a pipette full and get a refract reading. Then once i have an sg reading i use a hydrometer/temp conversion tool to get my true SG.

 

[kymba]

personally, i use whatever i have close at hand to dip into the mash / boil then let a few drops drip onto the prism. 2 drops of wort cool down a whole lot faster than a pippette or whetever else, especially after it has been flattened across the whole face of the prism. when i'm mashing i usually use my thermometer, when i'm boiling / whirlpooling it is the spoon. i dropped my 1st pipette in the boil and never found it again <_<

and are you using a correction table for your readings? theory is that alcohol affects the rafraction differently than sugar, so you need a correction table to look up your SG + current reading = real gravity. or have brewmate handy and use the calculator in there

 

[Fat Bastard]

However , i just wanted to say , you don't have to set this weekend in stone to bottle....if it's not ready to bottle , it's not ready...
Better to get 3 days of the same reading before you bottle..and not have bottle bombs...

Not set in stone, but this is the second week it's been in secondary after a week in primary. The SG hadn't moved in over a week! Dropped some hops in on Sunday and that looks like it's stirred it up a bit. A little mini Krausen has appeared on top, so I'm hoping it'll have dropped some more. Will start taking readings again on Thursday. Temperature in the room has been quite low, 16-17 degrees constantly.

do you use a hydro/temp calculator to calculate a true reading?
Heres what i do, when i take a sample of wort from my kettle i fill a test tube and let it sit on the bench until im ready to measure it. I drop a digital thermometer into it as well. I usually leave it around 1/2 hour or so and all the trub has sunk to the bottom. I then take a pipette full and get a refract reading. Then once i have an sg reading i use a hydrometer/temp conversion tool to get my true SG.

personally, i use whatever i have close at hand to dip into the mash / boil then let a few drops drip onto the prism. 2 drops of wort cool down a whole lot faster than a pippette or whetever else, especially after it has been flattened across the whole face of the prism. when i'm mashing i usually use my thermometer, when i'm boiling / whirlpooling it is the spoon. i dropped my 1st pipette in the boil and never found it again <_<

and are you using a correction table for your readings? theory is that alcohol affects the rafraction differently than sugar, so you need a correction table to look up your SG + current reading = real gravity. or have brewmate handy and use the calculator in there

Didn't use any temperature correction tools, but I calibrated with RO that was at ambient temp, same as the water in the glass. Because I don't trust my refract readings, I've been measuring the SG in ferment with the hydro. I'll take a few on Thursday from both beers and see how it is going according to the brewmate calculator, and both before and after settling. I probably need to do this anyway, as I'm a constant checker and I'm losing a lot of beer to hydrometer readings!

 

[bignath]

Didn't use any temperature correction tools, but I calibrated with RO that was at ambient temp, same as the water in the glass. Because I don't trust my refract readings, I've been measuring the SG in ferment with the hydro. I'll take a few on Thursday from both beers and see how it is going according to the brewmate calculator, and both before and after settling. I probably need to do this anyway, as I'm a constant checker and I'm losing a lot of beer to hydrometer readings!

Not temp correction tools, but refractometer alcohol correction tools.

You can use a refractometer to measure any liquid around the house that doesn't contain alcohol and trust that the reading would be correct. But, once alcohol is present you need to use a correction tool calculator or table to account for this.

It's a little bit of a pain in the arse, however the big plus is speed of taking a reading, small sample required for the reading, and you can take readings of every part of the brewing process.

Unfortunately i can't find the link to the correction table i use, but i'm sure someone will be along to provide some soon.

 

[MaltyHops]

Unfortunately i can't find the link to the correction table i use, but i'm sure
someone will be along to provide some soon.

Maybe this one? Refractometer Sg-alcohol Correction Chart

Also note:

If you're talking about fuzzy readings on the refrac, I think that would be
due to yeast in the sample that gets onto the refrac's crystal. If you draw
say a spoonful or so of the wort and put that in the fridge for 10mins or
so, and then take a reading, you ought to get a sharp reading.

Make sure your pipette is completely dry before drawing up any samples
as a little bit of water could have a drastic effect on the SG reading since
a very small amount is used for measuring. After taking a reading, I usually
flush the pipette a few times with water and then flush as much water out
as possible before letting it dry out.

And that you collect a sample from an even spot - i.e. not from a spot that
has very high or very low sugar for some reason. And if a sample gets a
little frozen if being cooled quickly in the freezer compartment, chuck it and
start again.

T.

 

[Whiteferret]

I've had the same reading variations too

Make sure your pipette is completely dry before drawing up any samples
as a little bit of water could have a drastic effect on the SG reading since
a very small amount is used for measuring. After taking a reading, I usually
flush the pipette a few times with water and then flush as much water out
as possible before letting it dry out.

this is what I had decided was the problem. Next brew I am going to rinse the refrac plates with water and
dry with the soft cloth provided before taking the next sample.
I think there was still water on my refrac.
Trub on the plates just seems to make the blue area out of focus.

 

[vykuza]

Also remember that the temp of the wort when it goes on the prism isn't the big issue, but the temperature of the refractometer itself. The thermal mass from the refrac is going to cool down or warm up those few drops almost instantly; but if you've left your refrac sitting in the sun while you brew, your reading is going to be off. Your refrac will say at what temperature it was calibrated (most likely 20c) and you will need to compensate for any temps above or below that.

 

[MarkBastard]

With regards to water in the pipette I just take a bigger sample in a little cup and fill the pipette and then empty again a few times. I figure after doing this three times the sample in the pipette will have no more water droplets, only wort.

I'm finding my refrac very handy.

 

[jacknohe]

I love my Refrac! Its Orsum. I got one that only reads in BRIX but have found it works well for me. Like others mention above, I don't bother with trying to cool down the sample before placing drops on the prism which was a reason I bought one. The only times I use the Refrac are:

- Post Mashout but Pre-boil
- Post boil
- Before yeast pitching (with a Hydro reading if I'm not confident for any reason)

I find I can follow the Boil-off by using the calculators in Beersmith from mash to pitching. Just need to make sure the Refrac is cleaned between each reading. However, I calibrate each brew day with tap water. Not sure if my thinking is right, but I figure I'm using tap water in the mash which should be my zero point.

I don't bother with using the Refrac after yeast pitching due to the Alcohol and additional calculations involved. I've read that its not always that accurate.

 

[white.grant]

I've had the same reading variations too


this is what I had decided was the problem. Next brew I am going to rinse the refrac plates with water and
dry with the soft cloth provided before taking the next sample.
I think there was still water on my refrac.
Trub on the plates just seems to make the blue area out of focus.

Yes indeed. I used to find suprising readings with my refractometer during the brew. Often the FG would be way off the anticipated reading but a subsequent reading later on when pitching would see it back to where it should have been.

I tested my refractometer after I had "cleaned" (rinsed in bucket of water, dried on front of t-shirt) it after use. I managed to measure the sg of tap water at about 1028! Seems there was still some wort on the plate. Now I rinse it thoroughly and dry it carefully before use and my readings are as expected.

cheers

Grant

 

[Fat Bastard]

Not temp correction tools, but refractometer alcohol correction tools.

You can use a refractometer to measure any liquid around the house that doesn't contain alcohol and trust that the reading would be correct. But, once alcohol is present you need to use a correction tool calculator or table to account for this.

It's a little bit of a pain in the arse, however the big plus is speed of taking a reading, small sample required for the reading, and you can take readings of every part of the brewing process.

Unfortunately i can't find the link to the correction table i use, but i'm sure someone will be along to provide some soon.

I've seen that chart and tried in the past to use it to correct the ferment readings and it read low compared to the hydro, so stopped using it.

Took a small sample of the IPA tonight and corrected for temp and alcohol using the brewmate tools and got 1.020,which tallys with brewmate's estimate of what it should be. Using the chart it works out at 1.010. I'd say it's finished and will be bottling this weekend if I'm brave enough to trust the refrac'.

Is the brewmate calculator trustworthy?

I measured it 3 times too, to make sure I had my technique down.

For future wort readings, I'll be taking a small sample and allow it to settle before trying to use it. I'm thinking suspended particles in the wort may have some effect on the reading, and using some other implement other than a pipette to transfer to the prism. That should sort out any chance of dilution from previous samples.

I've been cleaning the prisim and plate in clean water and drying off with a soft cloth, so I'm pretty sure that's not causing the issues, and the brew bench is out of the sun. I'll be putting another brew down the week after next, so I guess I'll find out if I've got the hang of it then!

Cheers,

FB