Hydrometer Reading

[seemax]

The hotter the liquid the lower the SG reading.

The volume of the liquid increases with temperature, therefore the apparent density decreases (same amount of contents dissolved in a larger volume).

20C higher results in a reading 5 points lower (approx).

 

[Supra-Jim]

Isn't it the other way round?

http://www.howtobrew.com/appendices/appendixA.html

[Taken from Palmers page:

If the wort temperature is 108 F, and the gravity of the sample is 1.042, the Delta G value that would be added is between .0077 and .0081. Rounding it off to the third decimal place gives us .008, which is added to 1.042 yielding 1.050.

I believe when he says gravity of the sample is 1.042, he means "measured gravity" of the sample. And then he goes on to work out the correction factore, 0.008, which he adds to his "measured gravity" to give an "actual gravity" of 1.050]

By this reasoning, if the temp of the sample is higher than the calibration temp of the hydro, the reading will be lower than what is should be.

Specific gravity is a function of density, the warmer a fluid is, the lower the density, hence the hydrometer sinks further into the fluid and registers a lower reading.

Cheers SJ

 

[muckey]

as stated hotter liquids are less dense.

the difference in readings taken by the OP couldn't possibly be temperature related due to the huge varience in reading.

I'd say that poorly mixed wort or a dodgy hydrometer is going to be closer to explaining this

 

[Pennywise]

Ahhhh, I must have read that HTB page backwards. I remember last summer I had quite a few brews pitched at 26, and had to add a couple of points to my OG reading because I was obviously getting lower than correct readings.

 

[buttersd70]

warmer sample, higher reading....
according to beersmith;
for a 15c hydro, 1050 @ 42C = 1042 @ 15C
for a 20c hydro, 1050 @ 45C = 1042@ 20C

In either case, thats a hell of a temp difference required.

duh, change first line to warmer sample will give lower reading.
and
for a 15c hydro, 1042 @ 42C = 1050 @ 15C
for a 20c hydro, 1042 @ 45C = 1050 @ 20C

Put your glasses on, Butters... B)

 

[muckey]

Put your glasses on, Butters... B)

have a beer and settle yourself

 

[chappo1970]

Put your glasses on, Butters...

I see you have started :icon_drunk: early today Butters! Good on you for taking one the workin man!

Cheers

Chappo h34r:

 

[buttersd70]

I see you have started :icon_drunk: early today Butters

Not at all....I have pneumonia atm, can't think particularly straight.

 

[chappo1970]

Not at all....I have pneumonia atm, can't think particularly straight.

ROFL!

Yes, yes of course you have the flu.......

 

[Fourstar]

you need both so you can show off the bling to non brewing plebs and they will see how intelligent and skilled you really are!!!

Nope, you need both so you can calcuate the starting gravity of megaswill so you may clone it for said 'non brewing pleb' friends.

no seriously though, any decent beer i want to clone i will do this. I think its better than guessing and gives you an idea for the ballpark of required mash temps, yeast attenuation, grist etc. Its a good starting point as you will now know the OG, FG and true ABV (as whats listed on the bottle is allowed to be out by .2% from memory).

Cheers.

 

[muckey]

good post fourstar

some info of the differences would probably help some of the less experience brewers as both hydrometers and refractometers have their uses. Unfortunately I'm not the best person to provide it

 

[Ivan Other One]

Whould all this really matter?

If the OG and the FG readings were both taken at the same temp,, Say for example, 22C then the differnce would still be the same, and then one could still calculate alc%.

Please correct me if I am wrong so next time I get it right.

 

[Screwtop]

Ok, lets try another tack.

So shaunms takes the temp of his wort @ 37C the reading is 1.050

If his Hydrometer is a calibrated at 15 then according to Palmers Hydrometer Temperature Correction Table

Reading 1.050 + 0.0058 = 1.0558 = Corrected gravity reading of 1.0558

Now later on he takes a reading and the wort has cooled to say 27C and the reading is 1.042

Again for a hydro calibrated at 15C and using Palmers Hydrometer Temperature Correction Table

Reading 1.042 + 0.0026 = 1.0446 = Corrected gravity of 1.0446


Has the penny dropped for anyone yet?

Temperature corrections must always be taken into account for a hydro reading if not taken at the calibrated temperature. shaunms' problem is that the reading was different. You cant solve the problem of the difference using temperature correction. The reading should always be the same only the corrected value should be different.

Gets em every time :lol:

 

[bum]

You're saying the wort in his fermenter (two different samples) is going to drop 10 deg C in 20 minutes? Christ, I wish mine did that!

 

[the_yobbo]

Wow, ask a simple question, get a variety of answers that lead to more questions

So, temperature correction on hydrometers. Is the correction table a generic thing or does each brand/model have its own correction cooefficient? I picked up two hydrometers second hand, without any additional paperwork/tables. Can I use any correction table found on the web?

 

[muckey]

yes you can

the hydrometer is rated/calibrated at a certain temp - should be branded on each.
the required correctionis based upon how much the density of the wort changes with temperature

you just need to know what the hydrometer is calibrated to so you know how much adjustment is required

 

[Nick JD]

Why do you care what the OG is for K&K? What do you need this number for?

 

[buttersd70]

Why do you care what the OG is for K&K? What do you need this number for?

two reasons. First, to work out the abv...if thats of any interest. Secondly, and more importantly, to be able to see what the attenuation is, to be able to compare that to the fermentables used, to see if the final gravity is within reasonable expectation for the yeast used. This will give you an indication if stable gravity readings means it's finished, or if it's stalled.

 

[manticle]

And third - to get your head around processes that might become more important later. Why develop bad habits when you can develop good ones?

 

[chappo1970]

Eggsactery Butters and Manicle!

and saves you from the now famous but never not amusing "WHY HAS MY AIRLOCK STOPPED BLOOPING?"


Cheers

Chappo :icon_cheers: