Confused about recent refractometer readings

[pretzelb]

I'm willing to admit this might be stupid user error but I just finished a batch and I am totally lost on my refractometer. I had an issue with a previous batch and got some help in this forum that convinced me I needed to pay closer attention to my SG. So that is what I tried to do. But here's what I found when using my refractometer:

• Collected 6.5 g after sparge and measured it at 11 brix or 1044 which was off the 1056 from BeerSmith
• After 30 minutes of boil I had about 6 g left and my reading was 12.8 brix or about 1052
• At 40 minutes into the boil I'm down to about 5.75 g and my reading is 12 brix?
• After an hour of boil I'm reading 12.8 brix again
• After 90 minutes of boil (it was only supposed to be 60) I had 12.8 brix again with about 4.9 g left

I did calibrate my refractometer back when I got it as the instructions told me to with distilled water. It is this model which should correct for temp so I'm not sure what I could be doing wrong.

So could this be I'm a stupid user or is this maybe an issue with the refractometer? Related to the stupid user part, is there any tool that is totally idiot proof for gravity readings? I had a cheap hydrometer to start but I don't know if the expensive hydrometers are any better when it comes to pre boil and pre chilling gravity readings on hot wort.

 

[HarkinBanks]

How many lbs of grain did you use?

Depending on where you sample, your readings can vary. You also have to let the sample cool for about 2-5 minutes to get a truly accurate reading.

 

[pretzelb]

This last batch was around 12 lbs of grain. Would that make a difference?

When I took samples I tried to make sure the wort was mixed so it was accurate, but that only really applies during pre boil when you're adding your first and second runnings. After that I assume the boiling kettle keeps the wort mixed up well.

Wouldn't a refractometer with temperature correction be fine reading wort no matter the temperature?

 

[HarkinBanks]

With 12 lbs you should be getting to around roughly 1.049 pre-boil gravity with 6.5 gallons collected, so you either had a slightly inefficient mash/sparge or you just got a light sample.

If I get a light sample, I usually test again after I stir it up. During the boil, you can sometimes get a light sample as well, so I test a few times.

You are right, if you have a refractometer with ATC it corrects the sample, but I was just saying it takes a good 2 minutes to get a true reading when you sample boiling wort.

 

[pretzelb]

With 12 lbs you should be getting to around roughly 1.049 pre-boil gravity with 6.5 gallons collected, so you either had a slightly inefficient mash/sparge or you just got a light sample.

If I get a light sample, I usually test again after I stir it up. During the boil, you can sometimes get a light sample as well, so I test a few times.

You are right, if you have a refractometer with ATC it corrects the sample, but I was just saying it takes a good 2 minutes to get a true reading when you sample boiling wort.

I should say that I entered the recipe into BeerSmith and then went off the calculations from that software. I can get those exact figures if necessary.

I agree that at first I also assumed very inefficient mash/sparge. It's not going to be a surprise since I batch sparge. I fully intended on starting a new post asking on how to get better at my mash/sparge because I fully assumed that was the source of my troubles. But after my readings I'm not sure I can really be sure of anything.

So when you say 2 minutes, what is your procedure? Are you using a dropper and then just letting it sit for a few minutes?

Also, I wonder if my cleaning routine isn't good enough. I was washing with tap water and some soft cloth to clear up the refractometer. After my readings would go up then down then up again, I started to question if my cleaning ritual was flawed.

 

[HarkinBanks]

My rough numbers were based on 73% efficiency. You need to really dial in Beersmith to get accurate numbers with batch size, boiloff amount, deadloss, etc. If these aren't dialed in, the program will give you high numbers.

I just use the dropper and let it sit for a minute or two. It always goes up a few tenths of a point from when I first look at it after it cools. Washing with tap water is fine.

I'd say chalk this one up to experience and go brew again and take a few more readings next time if they seem light.

 

[jason.mundy]

Are you cleaning your refractometer between uses? Like with starsan or water? If so, is the refractometer completely dry when you add your next sample?

It is possible to dilute your sample if you refractometer is still wet with water or starsan. It doesn't take much with such a small sample.

I've also had problems if there were air bubbles under the flap. Double check for that as well.

I would keep on taking samples until I get two readings that match.

 

[pretzelb]

My rough numbers were based on 73% efficiency. You need to really dial in Beersmith to get accurate numbers with batch size, boiloff amount, deadloss, etc. If these aren't dialed in, the program will give you high numbers.

I just use the dropper and let it sit for a minute or two. It always goes up a few tenths of a point from when I first look at it after it cools. Washing with tap water is fine.

I'd say chalk this one up to experience and go brew again and take a few more readings next time if they seem light.

As far as dialing in BeerSmith goes, it's a catch 22 if I can't use my tools correctly. I suppose I might be able to calculate boil off more accurately but I thought gravity was a pretty decent constant but that assumed I was using the refractometer correctly.

I'm actually OK with light readings at the startsince I am batch sparging and that should be not very efficient. What I can't accept is that my readings would go down or never go up after more and more of my wort was boiled off.

 

[jwright]

Also,
Not to restate the basics, but what is your sample technique?
Are you using a new (dry) pipette each time or are you rinsing the existing one - 1 drop of rinse water in a pipette of 5-6 drops makes a huge difference. I have also had problems if I just "spoon" some off the top - steam/water vapor tends to dilute the sample.
Sorry if I am restating the very obvious - just some observation from my many attempts to dial in my new refractometer.
Now if someone has tips for making a sharper demarcation line, I would be happy.
Jason

 

[pretzelb]

Are you cleaning your refractometer between uses? Like with starsan or water? If so, is the refractometer completely dry when you add your next sample?

It is possible to dilute your sample if you refractometer is still wet with water or starsan. It doesn't take much with such a small sample.

I've also had problems if there were air bubbles under the flap. Double check for that as well.

I would keep on taking samples until I get two readings that match.

I did clean the refractometer between each use. I really made sure I did a decent job after I saw the reading go from 12.8 to 12. I also did try to dry completely. I also let it air dry on top of that to give the drying process more time to work. I used tap water for the cleaning.

I did worry about air bubbles but at the time I started to question if tap water was valid for cleaning and even question how I was collecting my sample. I didn't think this was rocket science but after 1.5 g was boiled off and I could not get a higher reading I was extremely frustrated.

 

[cheezydemon3]

Alright.

Clearly, your first problem, is that you own one of those thingies....................

All in good fun, but...............the day I buy one of those, is the day I have lost sight of what is important......unless............ you are a card carrying nerd.

................

(here I am, shooting light refracting rays from my squinting EYE!)lol.

 

[pretzelb]

Also,
Not to restate the basics, but what is your sample technique?
Are you using a new (dry) pipette each time or are you rinsing the existing one - 1 drop of rinse water in a pipette of 5-6 drops makes a huge difference. I have also had problems if I just "spoon" some off the top - steam/water vapor tends to dilute the sample.
Sorry if I am restating the very obvious - just some observation from my many attempts to dial in my new refractometer.
Now if someone has tips for making a sharper demarcation line, I would be happy.
Jason

I was re-using the pipette after rinsing it under the tap and doing my best to make sure it was dry afterwards. It's very possible that is part of my problem. But I'm not sure what would be a better method. Maybe I'm just being stupid when it comes to how to collect the drop for a sample.

 

[pretzelb]

Alright.

Clearly, your first problem, is that you own one of those thingies....................

All in good fun, but...............the day I buy one of those, is the day I have lost sight of what is important......unless............ you are a card carrying nerd.

................

(here I am, shooting light refracting rays from my squinting EYE!)lol.

And I've thought that very thing. It could be that my attempt to make life easier instead made it more difficult. I assumed collecting gravity readings would be easier with a refractometer but thus far I get a big fat F on that front.

 

[jwright]

Pretzelb -

I'll admit I'm a wanna be nerd when it comes to brewing. I love the measuring and the science.

As far as the sampling technique - the rinsing may be part of the problem, any additional amount of SG 1.00 liquid will really lower your reading. I find it very difficult to compleetly empty and dry those pipettes

I am still looking for a supply of the cheap disposable pipettes. I remember seeing them for a few dollars/100. That is the ideal method, a fresh new pipette for each measurement.

In the meantime, what works for me is to completely fill and expel the pipette 3-5 times with wort, then measure. I just stick the end of the pipette into the boil and squeeze-release, squeeze release x3, trying to fill and empty the pipette each time. That way, any residual rinse water is minimized.

I am sure some of the lab rats here can chime in on the 'proper' number refills to minimize errors, but it works for me.

I don't have any helpful explanation for your results - Just wanted to pass along a simple tip that has seemed to help one of my difficulties. And I still make sure to grab a hydro pre and post SG.
jason

 

[pretzelb]

In the meantime, what works for me is to completely fill and expel the pipette 3-5 times with wort, then measure. I just stick the end of the pipette into the boil and squeeze-release, squeeze release x3, trying to fill and empty the pipette each time. That way, any residual rinse water is minimized.

I am sure some of the lab rats here can chime in on the 'proper' number refills to minimize errors, but it works for me.

I don't have any helpful explanation for your results - Just wanted to pass along a simple tip that has seemed to help one of my difficulties. And I still make sure to grab a hydro pre and post SG.
jason

Thanks for that idea. I think I did try that but I didn't record if that made a difference. I was getting frustrated and I knew I had several variables that could be the problem so I wasn't sure which to try and change. It could be the answer is as simple as the squeeze release x3 method.

I also debated using a small pyrex measuring cup to scoop some wort out and then dripping a drop or two using my finger. But I wasn't sure if that would be a valid sample method.

I may have to see if I have any spare DME around and if so run a test with some boiling water to see if I can get readings that make sense (i.e. gravity goes up as boil time increases).

 

[HarkinBanks]

Once you chilled, did you take a hydrometer reading to confirm everything? I also do this before I pitch my yeast.

RDWHAHB, your gravity had to go up the longer you boil, it's science. This is all a good excuse to go brew another batch.

 

[GilaMinumBeer]

ATC DOES NOT correct for sample temp!

ATC corrects ONLY for the temperature of the instrument (EDIT) within a given range.

http://cefresno.ucdavis.edu/files/43066.pdf

 

[pretzelb]

ATC DOES NOT correct for sample temp!

ATC corrects ONLY for the temperature of the instrument.

http://cefresno.ucdavis.edu/files/43066.pdf

Well this could be the problem.

6. Check to make sure that an ATC refractometer was used within its range of 68-86ºF.

I'm brewing in the garage/driveway and yesterday it was chilly in the low 40s.

So one thing I may need to change in my procedure is leave the refractometer in the house and then bring the sample inside for measurement.

Nice article. Thanks for that.

 

[GilaMinumBeer]

Well this could be the problem.



I'm brewing in the garage/driveway and yesterday it was chilly in the low 40s.

So one thing I may need to change in my procedure is leave the refractometer in the house and then bring the sample inside for measurement.

Nice article. Thanks for that.

Yep. It's a all too common misconception about ATC on refractometers and pH meters. Plus, always check the cal on brewday in the environment you take the sample.

 

[jason.mundy]

Keep it in your inside coat pocket

 

[pretzelb]

In case anyone cares here is some follow up to this thread.

I brewed today and kept the refractometer inside the house so it's at room temperature. My readings were low but close to expected so I thought I was on the right track. I was upset to see that after 15 minutes from the start of boil my 9.2 pre-boil brix reading was still 9.2 brix.

So I tried something different. I took a small Pyrex cooking glass and I took a small amount of wort inside. I then tested it hot and tested it again after a few minutes. The hot sample was 9.2 but after it cooled it was 9.8 or maybe even 10.

I'm guessing that ATC doesn't really work for really hot work. I need to test this some more but for now my procedure is going to be to take the sample inside and then look at it after 5 minutes.

 

[GilaMinumBeer]

In case anyone cares here is some follow up to this thread.

I brewed today and kept the refractometer inside the house so it's at room temperature. My readings were low but close to expected so I thought I was on the right track. I was upset to see that after 15 minutes from the start of boil my 9.2 pre-boil brix reading was still 9.2 brix.

So I tried something different. I took a small Pyrex cooking glass and I took a small amount of wort inside. I then tested it hot and tested it again after a few minutes. The hot sample was 9.2 but after it cooled it was 9.8 or maybe even 10.

I'm guessing that ATC doesn't really work for really hot work. I need to test this some more but for now my procedure is going to be to take the sample inside and then look at it after 5 minutes.

I use a "coors" plate. It's a dimple ceramic sample plate. Mine has 10 dimples but, they come in a variety of shapes. Basically, I draw samples into my coors plate to let them cool to room temp and then take refr' readings from the cooled samples.