Gravity Readings – what the hell am I doing wrong!

[bazfletch3]

[SIZE=medium]Hi All[/SIZE]

[SIZE=medium]I need some help with what I presume is something incredibly stupid I am doing wrong……The last few brews I’ve started making a conscious effort to “measure & control” things more. I grabbed Beersmith to help with my recipe creation and record keeping, and I’ve been taking gravity readings much more often through my brewing process – rather than just at the end before I pitch yeast! Problem is I can’t make any sense out of my numbers – they seem all over the shop![/SIZE]
[SIZE=medium]I just have the basic el-cheapo hydrometer that came with my starter kit from Grain & Grape years ago (I somehow haven’t broke it yet), along with a glass thermometer from G&G as well. I just use the plastic hydrometer tube for my samples – I take a temp reading, then the hydrometer reading, then double check temp again. I then just use the Beersmith temp correction tool to find my “real” gravity reading.[/SIZE]

[SIZE=medium]However on the last couple of brews, the (corrected) reading I’ve taken pre boil (at 50 ish deg’s after sparging) has been higher than the “final” OG reading I’ve taken from the fermenter just prior to pitching (at 18 deg’s – with no correction). I know this can’t physically be possible so something must be up. In these cases I’ve gone from thinking “ok, my efficiency is better than Id anticipated”, to “shit, now my numbers are lower than I was shooting for”.[/SIZE]

[SIZE=medium]My thoughts are that either:[/SIZE]

• [SIZE=medium]My hydrometer is dodgy (at higher temps?)[/SIZE]
• [SIZE=medium]My thermometer is dodgy[/SIZE]
• [SIZE=medium]The wort sample isn’t mixed properly after I’ve batch sparged and I’m measuring a sample which has more “first runnings”[/SIZE]
• [SIZE=medium]Taking gravity readings at higher temps is always inaccurate and I should be cooling all my samples down to 20ish deg’s before measuring[/SIZE]
• [SIZE=medium]I’m playing the wrong music whilst brewing[/SIZE]
• [SIZE=medium]I’m not drinking enough whilst brewing[/SIZE]

[SIZE=medium]If anyone has any ideas for me it would be very much appreciated – I do enough swearing on brew day as it is without something as basic as gravity readings messing with my head as well![/SIZE]

[SIZE=medium]Cheers[/SIZE]

[SIZE=medium]Baz[/SIZE]

 

[bundy]

I wouldn't trust the temp corrected reading with a hydrometer and I also would t trust a single reading as sometimes they are wrong. Temp adjusted gravities are notoriously inaccurate. Good for a guide but you are far better (and safer) to cool your sample first.

For my process each gravity reading is cooled before I test. (Also far safer than putting glass in very hot wort they can and do crack) I just take a sample and put in the fridge or even place in a cool tub of water or ice to bring down to around 20 degrees.

If one reading seems way out of whack I'll often take a second sample just to double check as I Have been caught out this way before also.

Hope that helps

 

[pcmfisher]

What gravity readings did you get and at what temp?

What were you expecting?

 

[bazfletch3]

I wouldn't trust the temp corrected reading with a hydrometer and I also would t trust a single reading as sometimes they are wrong. Temp adjusted gravities are notoriously inaccurate. Good for a guide but you are far better (and safer) to cool your sample first.

For my process each gravity reading is cooled before I test. (Also far safer than putting glass in very hot wort they can and do crack) I just take a sample and put in the fridge or even place in a cool tub of water or ice to bring down to around 20 degrees.

If one reading seems way out of whack I'll often take a second sample just to double check as I Have been caught out this way before also.

Hope that helps

Thanks! - Sounds like thats my theory going forward; draw off a couple of samples and cool them down first.

What gravity readings did you get and at what temp?

What were you expecting?

Was shooting for 1.046 pre boil and 1.055 post. All my volumes worked out perfect through the mash and boil. My measured reading pre boil was 1.044 (taken at 50deg) - which Beersmith "corrects" to 1.055, and then a straight out reading of 1.048 post boil in the fermenter at 18deg.

So Im going to presume that my OG reading of 1.048 is "correct"; while the pre boil reading is dodgy. - And that my efficency is lower than Ive punched into Beersmith.

Cheers

Baz

 

[sponge]

Have you tested your hydro in room temperature water and confirmed it reads 1.00?

It's best to cool down a hydro sample (as previously mentioned) or grab yourself a refractometer. You'll never look back.

 

[Blind Dog]

If you want to calibrate, You should really do a 2 point calibration, pure water at your hydrometers calibrated temp (often 20C) being the first and should read 1.000. A sucrose solution is the other (eg 10% sucrose solution is 1.040 or 10 degrees Plato).

 

[stux]

Best to cool a hydro sample. Never found the temp corrected readings very accurate, unless the temp is close enough to 20C not to matter!

Also, when you're cooling the sample, stick some gladwrap over your sample tube to prevent evaporation which will concentrate the sample.

 

[verysupple]

My measured reading pre boil was 1.044 (taken at 50deg) - which Beersmith "corrects" to 1.055,

According to my calculations, it seems as though Beersmith has the calibration temp. set to 15 C. You should check if your hydrometer is calibrated for 15 or 20 C. This isn't the major cause of your problems as it'll only change the value by ~0.002, but you may as well make sure the software is setup properly (assuming Beersmith allows you to change it).

 

[hoppy2B]

Could be that you're taking the temp measure incorrectly. Or perhaps your thermometre is dodgy.

Your temp reading at 20C is likely to be accurate, as temp is normally correct when the stem of the thermometre is at 20C with the bulb held in the liquid.

 

[billygoat]

When I take a pre boil sample to check the gravity, I give the kettle a bit of a stir. I have found that during sparging there appears to be stratification or layers of different gravity and temperature throughout the kettle.
I found if I give the kettle a stir it mixes up the layers and I get a more accurate measurement. I also cool the sample.

 

[bazfletch3]

Exactly what I was hoping to get- great ideas. Thanks all!

 

[Ducatiboy stu]

You are definatly playing the wrong music.

 

[DU99]

:icon_offtopic: Thermometer is easy to check place in boiling water...i had thrown a few dodgy digitial ones out..because of temp difference's

 

[Brendandrage]

I had a glass thermometer at first and it was nearly 10 deg over temp, obviously this had a massive impact on my brew and the suspected readings , I have since purchased a mash master analogue, digital meat probe, and a the stc1000 and these 3 are all within .5 deg of each other and I regularly check them against each other, might be worth a try as well.

 

[Black n Tan]

• My hydrometer is dodgy (at higher temps?) Pretty unlikely I would have thought. I would expect the hydrometer to read wrong at both gravities.
• My thermometer is dodgy Possible, but it is unlikely to cause such a dramatic variation in gravity.
• The wort sample isn’t mixed properly after I’ve batch sparged and I’m measuring a sample which has more “first runnings” This is the likely cause in my book. As billygoat mentioned you can get stratification and you should give it a good mix before taking the sample.
• Taking gravity readings at higher temps is always inaccurate and I should be cooling all my samples down to 20ish deg’s before measuring. Unlikely to be responsible for such a large variation, although I think it is more accurate to cool your samples first.

And in my personal opinion a refractometer is not the solution. I more often get spurious results with a refractometer than with a hydrometer. It is now mothballed.

 

[Flash_DG]

Also if you are taking a sample right from the kettle before you boil tip the first few mls back into the kettle straight from the tap then draw off a sample.
Me I use a 1 cup pyrex cup for my samples just scoop from the top after a good stir then put that in some water to cool to about 40 to 30 degrees.
Also check where you take the readings from on the hydrometer. Mine says "Reading Under Meniscus" which can make it really hard to get when you got bubble and/or dark wort.

 

[Judanero]

Calibrate your thermometer (Boiling water test to read ~ 100c depending on your altitude, cup of ice slurry to read 0c).

Calibrate your hydrometer as suggested previously.

Also just in case you're not already doing it, double check your hydrometer isn't touching any of the sides of the tube- the plastic ones that house the hydrometer don't have much room for play.

With the gravity sample you're taking during the brew day, does the sample appear to have much/any break in it? Could that account for one is higher than your final sample? Ie- final sample is clearer wort

 

[bazfletch3]

You are definatly playing the wrong music.

I did have mishap where our daughter turned off my playlist and that song from Frozen started playing at very high volume - I hope to christ I havnt ruined this brew?

I had a glass thermometer at first and it was nearly 10 deg over temp, obviously this had a massive impact on my brew and the suspected readings , I have since purchased a mash master analogue, digital meat probe, and a the stc1000 and these 3 are all within .5 deg of each other and I regularly check them against each other, might be worth a try as well.

:icon_offtopic: Thermometer is easy to check place in boiling water...i had thrown a few dodgy digitial ones out..because of temp difference's

I had naively thought that a half decent glass thermometer would be "accurate enough" as a reference - I’ve read plenty of bad things about cheap digital ones. But I'll do some referencing just to make sure. I think one of the gold plated thermopens might be my next birthday present, it annoys me no end waiting and staring at the mercury to see if it’s still rising or not.

• My hydrometer is dodgy (at higher temps?) Pretty unlikely I would have thought. I would expect the hydrometer to read wrong at both gravities.
• My thermometer is dodgy Possible, but it is unlikely to cause such a dramatic variation in gravity.
• The wort sample isn’t mixed properly after I’ve batch sparged and I’m measuring a sample which has more “first runnings” This is the likely cause in my book. As billygoat mentioned you can get stratification and you should give it a good mix before taking the sample.
• Taking gravity readings at higher temps is always inaccurate and I should be cooling all my samples down to 20ish deg’s before measuring. Unlikely to be responsible for such a large variation, although I think it is more accurate to cool your samples first.

And in my personal opinion a refractometer is not the solution. I more often get spurious results with a refractometer than with a hydrometer. It is now mothballed.

The wort stratification thing makes sense to me too after giving it more thought. I cant remeber the numbers but I remember taking a measurment with the hydrometer just floating in the BK which I think gave a copmpletey diffeerent reading to my drawn off sample. I drain the MT using gravity and a tube which curls to the bottom of the BK so it trickles in nice and gently so it probably hasnt mixed very well.

Also if you are taking a sample right from the kettle before you boil tip the first few mls back into the kettle straight from the tap then draw off a sample.
Me I use a 1 cup pyrex cup for my samples just scoop from the top after a good stir then put that in some water to cool to about 40 to 30 degrees.
Also check where you take the readings from on the hydrometer. Mine says "Reading Under Meniscus" which can make it really hard to get when you got bubble and/or dark wort.

I think you're right with the "meniscus" - although even if Im taking that wrong we're only talking 1 or 2 points - not a huge differential which I think Im dealing with here.

Calibrate your thermometer (Boiling water test to read ~ 100c depending on your altitude, cup of ice slurry to read 0c).

Calibrate your hydrometer as suggested previously.

Also just in case you're not already doing it, double check your hydrometer isn't touching any of the sides of the tube- the plastic ones that house the hydrometer don't have much room for play.

With the gravity sample you're taking during the brew day, does the sample appear to have much/any break in it? Could that account for one is higher than your final sample? Ie- final sample is clearer wort

I was actualy going to grab one of the fancy glass tubes with the nice thick wide base from G&G when I picked my ingredients but they were out of the small hydrometer sized ones - because yes, the plastic tubes are shit trying to get them perfectly straight so the hydrometer isnt touching the sides.

I think my wort sample is pretty clear of gunk and crap; so I think any problem with the sample may be more from an unever mix.......

 

[stux]

Was about to suggest a thermapen

http://thermapen.co.uk

I got mine because i was frustrated with brewing temps, and my glass thermometers were too slow and fragile.

Now I use the thermapen all the time

BBQ, roasting, brewing, deep frying, smoking sausages, grain temps

My wife steals my thermapen for baking and sugarcrafting!

 

[rude]

They look good Stux which one did you get the $100 one?