[GunniBrew]

Hey everyone, new to this forum and thought I'd post here to get some opinions on a problem I ran into recently.
I brewed the other day and broke my hydrometer right before I took my OG. Luckily, I always keep a spare, so it was no problem, took the reading and entered it into beersmith. This is where I ran into trouble, I had an efficiency drop of 10%, I consistently get 85% and today I was at 75%. I quickly came to the conclusion that since my hydrometer was the only factor that changed, it had to be the culprit. I found an article on BYO about performing a 2 point calibration, so I set it up and found that my new hydrometer was reading about 1 point low in DI water and about 4 points low in a 1.080 solution. I was blown away by how far off it was! Also, with my 4 point correction, my efficiency was bumped up to 80% for this brew day. So now I am left wondering how far off my old hydrometer was?!

Anyone else ever perform a 2 point calibration? And are you even concerned that your hydrometer readings could be potentially misleading?

Cheers

[yso191]

Hydrometer and refractometer errors are an old rant of mine.  I seriously dislike inaccuracy in measurement tools.  Having said that, my OCD is finally somewhat at peace with it.  I have just decided to use one hydrometer (I have 4, including three that are narrow range 'scientific grade').  Consistency is something.

[klickitat jim]

My method is to check it in DI occasionally and call it good. Unless you get the 1.080 calibration fluid from a reliable source, how do you know it's really 1.080? Once upon a time I tracked brewhouse efficiency and found mine to be 72%. I build my recipes on 72%, and I usually check OG when I brew and usually its within 2 or 3 pts. I'm pickier on new recipes because I want to know how new stuff is working. The gravity that I pay most attention to every time is FG. I usually don't care so much what the FG is, but that it is stable. On rebrews of old recipes,  I frequently forget to take an OG. But always the FG.

Its just one of the many cool things about homebrewing. If really geeking out on repeating stats is important to you, you can do that. If it's not, that's cool too.

[duboman]

Never done a 2 pt calibration, once a month or so I verify a 1.000 reading at 60oF in distilled water and adjust readings if necessary. If the hydrometer is way off I get a new one

Sent from my SAMSUNG-SM-G920A using Tapatalk

[Stevie]

Unless you get the 1.080 calibration fluid from a reliable source, how do you know it's really 1.080?

Not too hard using mass.
Well I guess that relies on a calibrated scale.
What if the calibration weight is off?
What if the scale isn't accurate across its full range?
What if I am testing in a gravitational anomaly?
This is too hard.
I need to lay down.

[GunniBrew]

Unless you get the 1.080 calibration fluid from a reliable source, how do you know it's really 1.080?

I guess I don't, I actually had a typo. I used 1.081 because thats 20 Brix. So knowing that, I used 20% sugar to  80% water (40 grams of sugar in 160 grams of water), so as long as my scale is well calibrated the solution should have been pretty close to 1.081. Or, at least close enough to be able to assume that my hydrometer is not off by the same number of gravity points in DI water as it is in solution.

Consistency and repeatability between batches is something that is pretty important to me, and they are totally achievable as long as you always use the same hydrometer, like yso191 said. But as soon as you have to change your hydrometer, from what I gathered with this ordeal, you either have to find out where your hydrometer is off or just deal with your numbers differing from what you are used to. It just seems to me, that it is such an important instrument and you can gain quite a bit from accurate readings. I don't know, the information I gained from this really just leaves me wanting more, because I absolutely cannot completely trust that the 1.081 solution I made. I don't know, maybe its just me.

[klickitat jim]

My hydrometer has a paper tube scale that slides if you gently tap it one end or the other. I calibrate at the stated temp (mine is 68F) in DI water. If it's off I tap it one way or the other till it's correct. Carefully so as not to break it.

I think if you want hyper accuracy you need the ones that are designed for that range, probably like Steve has. For me the only range that matters is 1.000-1.020. And really only matters that I can determine no change between samples.

[santoch]

Just Tap it:

https://www.youtube.com/watch?v=-br7JKuaZHQ

[pete b]

I no longer give a rat's ass about specific gravity.
EDIT: I meant to say I DO give a rat's ass about specific gravity.
EDIT: I meant to say I do give a rat's ass about specific gravity but ironically.

[pinnah]

tap tap tap aroo   

Hydrometers can be pretty inaccurate.
But if the same one is used consistently over time it can provide a reliable index.
 
Ya, that paper scale inside should not be moving.

Get a new one and the index numbers might change...takes a few data points to develop your new trend...

Are refractometers any different?




Pete, maybe you can give us a lesson on the difference between accuracy and precision. 

[crakers540]

Pete, maybe you can give us a lesson on the difference between accuracy and precision. 

Accuracy vs precision, ASTM?  Sensitivity vs specificity, GLP?

I have 2 hydrometers, use them both, and record the difference. They read 0.002 dif between them at 15C.

[crakers540]

meant to say use the average.

[Stevie]

Accuracy v precision

http://www.mathsisfun.com/accuracy-precision.html

In homebrewing, when I see precision hydrometers, the term isn't being used the same way. For hydrometers it means a narrower band of measurement with larger graduations. Example 1mm = .001° SG vs 1mm = .002° SG

[klickitat jim]

Just Tap it:

https://www.youtube.com/watch?v=-br7JKuaZHQ

Have you seen my hydrometer?  Ya, you'd tap that.