Happy HolidaySs Giveaway - Last Sponsor Giveaway of the Year!

Come Enter the BrewDeals/FastFerment Giveaway!


Home Brew Forums > Home Brewing Beer > Brew Science > Hydrometer reading vs Refractometer reading
Reply
 
LinkBack Thread Tools
Old 07-31-2011, 10:08 PM   #1
Mpavlik22
Feedback Score: 0 reviews
Recipes 
 
Join Date: Apr 2011
Location: Pittsburgh, PA
Posts: 316
Likes Given: 1

Default Hydrometer reading vs Refractometer reading

Whats up all?

I just got done brewing a Pale Ale (all grain). I just got a refractometer and decided to try it out. I still used my hydrometer to compare. I got completely different reading pre-boil & post-boil.

Before you ask, i did calibrate the refractometer with distilled water. Also it is a ATC (auto temp correction) unit. regardless since i take my hydro reading at 60 deg F, I cooled to 60 deg and took my hydro reading and refrac reading at the same time and temp.

Anyways my readings:
Pre Boil:
Target - 1.042
Hydrometer - 1.041
Refractometer - 1.033

Post Boil:
Target - 1.054
Hydrometer - 1.051
Refractometer - 1.043

So can anyone explain why my readings are so different between the hydrometer and refractometer?

Thanks

__________________
Mpavlik22 is offline
 
Reply With Quote Quick reply to this message
Old 07-31-2011, 10:57 PM   #2
jd3
Feedback Score: 0 reviews
Recipes 
 
Join Date: Apr 2011
Location: , The Back of the Bus
Posts: 443
Liked 8 Times on 7 Posts

Default

Is your hydrometer calibrated?

__________________
jd3 is offline
 
Reply With Quote Quick reply to this message
Old 07-31-2011, 10:58 PM   #3
Mpavlik22
Feedback Score: 0 reviews
Recipes 
 
Join Date: Apr 2011
Location: Pittsburgh, PA
Posts: 316
Likes Given: 1

Default

Yes hydrometer is also calibrated.

__________________

"If you fail to plan, then you plan to fail"

Mpavlik22 is offline
 
Reply With Quote Quick reply to this message
Old 07-31-2011, 11:06 PM   #4
jd3
Feedback Score: 0 reviews
Recipes 
 
Join Date: Apr 2011
Location: , The Back of the Bus
Posts: 443
Liked 8 Times on 7 Posts

Default

The only reading I take anymore is a OG and a FG. Why are you taking pre and post boil readings. I'd worry less about them and more about results.

__________________
jd3 is offline
 
Reply With Quote Quick reply to this message
Old 07-31-2011, 11:10 PM   #5
Yooper
Ale's What Cures You!
HBT_ADMIN.png
Feedback Score: 0 reviews
 
Yooper's Avatar
Recipes 
 
Join Date: Jun 2006
Location: Upper Michigan
Posts: 62,229
Liked 4774 Times on 3469 Posts
Likes Given: 948

Default

Quote:
Originally Posted by jd3 View Post
The only reading I take anymore is a OG and a FG. Why are you taking pre and post boil readings. I'd worry less about them and more about results.
A preboil reading is very useful. If you are way over or under on your target OG, you can fix it right then. You can also get your post boil OG just from doing some simple math from the preboil reading (If you have a preboil gravity of 1.060 with 7 gallons, for example, you KNOW what your gravity will be with 5.25 gallons in the fermenter), and adjust any hopping rates accordingly. You can also figure your efficiency from the preboil reading. Once you have your system completely locked in, maybe a preboil reading is less useful, but I wouldn't dismiss it.
__________________
Broken Leg Brewery
Giving beer a leg to stand on since 2006
Yooper is online now
MuddyCreek Likes This 
Reply With Quote Quick reply to this message
Old 07-31-2011, 11:14 PM   #6
jd3
Feedback Score: 0 reviews
Recipes 
 
Join Date: Apr 2011
Location: , The Back of the Bus
Posts: 443
Liked 8 Times on 7 Posts

Default

While I know there is a simple formula to get the reading post boil, I think it makes more sense to just take the reading.

I suspect the refractometer is either poorly calibrated, or just general poor quality and giving a bad reading. I use them in fish tanks and if they are the cheaper variety I can get different readings back to back.

Obviously one of the items is wrong. While I'd hope that the hydrometer is right since it is closest to the predicted readings, you would be a better judge of how things went.

I'd try it on some other known samples and go from there....

__________________
jd3 is offline
 
Reply With Quote Quick reply to this message
Old 08-01-2011, 12:29 AM   #7
Sithdad
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jul 2009
Location: Macungie, PA
Posts: 332
Liked 12 Times on 10 Posts
Likes Given: 4

Default

Get some distilled water and test both your hydrometer and your refractometer. Your refractometer may need adjusting. Also, some refractometers need to have their results adjusted based on a comparable hydrometer result. For example, after adjusting your refractometer you test a wort sample with your hydrometer and your refractometer. If, your temperature adjusted, hydrometer reads 1.040 and your refractometer reads 1.044 your refractometer has and adjusted wort value of 0.004. This would mean that all of your readings, from your refractometer, would require an additional 0.004 being added.

__________________
Sithdad is offline
 
Reply With Quote Quick reply to this message
Old 08-01-2011, 12:35 AM   #8
Mpavlik22
Feedback Score: 0 reviews
Recipes 
 
Join Date: Apr 2011
Location: Pittsburgh, PA
Posts: 316
Likes Given: 1

Default

As already stated I have calibrated both with distiller water

__________________

"If you fail to plan, then you plan to fail"

Mpavlik22 is offline
 
Reply With Quote Quick reply to this message
Old 08-01-2011, 12:53 AM   #9
iaefebs
Registered User
HBT_SUPPORTER.png
Feedback Score: 2 reviews
Recipes 
 
Join Date: Aug 2010
Location: West Coast, MI
Posts: 2,663
Liked 242 Times on 176 Posts
Likes Given: 605

Default

Quote:
Originally Posted by Mpavlik22 View Post
As already stated I have calibrated both with distiller water
I'm not sure what kind of an answer you are looking for. It seems people have trouble with refractometers. I don't know if it is because the newer cheaper ones have defects or if they are not getting the proper temp for a reading. I take a small sample of pre boil wort and place it in my ferment chamber for a few minutes then take a reading. I do the same post boil. When I sample during ferment I just insert a straw through the airlock hole to grab a sample. I hardly ever use a hydrometer untill it gives me an excuse to taste a sample. My refractometer is 5 years old.... maybe they made them better back then. I think you are experiencing temperature problems.
__________________
iaefebs is offline
 
Reply With Quote Quick reply to this message
Old 08-01-2011, 02:49 AM   #10
ajdelange
Senior Member
HBT_SUPPORTER.png
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2010
Location: McLean/Ogden, Virginia/Quebec
Posts: 6,253
Liked 629 Times on 519 Posts
Likes Given: 19

Default

Quote:
Originally Posted by Mpavlik22 View Post
So can anyone explain why my readings are so different between the hydrometer and refractometer?

Thanks
Refractometers are calibrated for sucrose solutions in water. Wort is not a sucrose solution. It contains a complex spectrum of sugars including some, but not very much, sucrose. A hydrometer is also calibrated against a sucrose solution. Thus neither instrument reads the true extract of the wort but density measurements track solution strength better than measurements based on refractive index i.e. a hydrometer reading will compare much more favorably to a true density reading made with an oscillating U-tube meter or pycnometer than a refractometer reading will. Refractometers really should not be relied on for anything other than monitoring the decline of extract as time progresses in sparging but home brewers insist on using them for a purpose to which they are not really suited. It must be said that the agreement between hydrometer and refractometer with wort is usually better than what you observed. In fact the agreement is often quite good but it is not unusual at all for them to disagree by a couple °P as in your case. The problem is you have no way of knowing whether the agreement is good or bad unless you make a comparative measurement in which case there is no point in taking the refractometer reading as you have to take a hydrometer reading to verify it. The exception to this is in commercial brewing where a calibration curve between refractometer and densitometer reading are made and used for a particular beer. When that same beer is brewed again a refractometer reading can be entered into the calibration curve and a good estimate of the extract taken out.

ATC may be partially responsible in your case. The ATC in a refractometer is based on the shift in refractive index of a pure sucrose solution relative to 20 °C (68 °F). Wort's refractive index does not shift at this same rate so all measurements with a refractometer should be taken with ATC turned off at a temperature of 20 °C. Not saying that this explains all your discrepancy but it might explain some of it. Another thought is turbidity. In the instruments where the light actually passes through the sample (the kind you look into) scattering may make the delineation between the dark and light parts of the field fuzzy. In the electronic instruments where the light never actually enters the sample you have better immunity to this effect.
__________________
ajdelange is online now
Malticulous Likes This 
Reply With Quote Quick reply to this message
Reply



Quick Reply
Message:
Options
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Hydrometer reading(FG)=1.010 Brix=7.1%??? ANewrBrewr Brew Science 7 04-02-2012 02:42 AM
Help reading water report cms Brew Science 1 03-08-2011 08:31 PM
hydrometer reading: change. batty Brew Science 9 01-11-2011 04:43 AM
Refractometer FG Readings a10t2 Brew Science 14 08-10-2010 07:03 PM
Take your OG reading before adding yeast... why? billc68 Brew Science 6 05-27-2010 02:30 PM



Newest Threads

LATEST SPONSOR DEALS