SG Readings

[bigpaul]

New to home brewing so please bear with me and apologise if this question has already been answered. When taking the SG of your beer...is the temperature important and can the temperature affect the actual SG? I was waiting for the final SG of my beer to be around 1012 as it had finished bubbling a day earlier. At 7am, I took a reading and it was 1015 (temperature at that time of the morning in Queensland was around 14 degrees) so I left it think it was still fermenting. At 3pm the same day, with the temperature around 26 degrees (All temperatures are taken from the thermometer on my fermenter) it had reached a perfect 1012. Can the temperature affect the SG this much or is it just coincidence that the beer had finished fermenting? this leaves me thinking that maybe I should take an OG reading at the same time / temperature as my FG reading?

Looking forward to your replies!

Paul

 

[Ducatiboy stu]

Yes temp will affect sg reading but not by that much

Use this to calc

http://hbd.org/cgi-bin/recipator/recipator/hydrometer.html?16305728

 

[bigpaul]

Nice 1 thanks for the reply...from what you have said I assume it is a combination of both the temperature and the fermentation coming to an end...will try and take all my readings when the temperature is in the mid 20's in the future??

Thanks again!

 

[bigpaul]

Actually, just sat there thinking about your reply...is there an ideal temperature to take OG and more importantly FG readings which would give a true reading and so negate the need to use the Hydrometer Temperature Correction?

 

[mmmyummybeer]

20C is the ideal temperature for taking gravity readings. Also for the FG reading it is better to degas the sample for a true reading.

 

[bigpaul]

Thank you...20 degrees it is then! Taking OG & FG readings from out my fermenter, not from kegs that have been gased, assuming that's what you mean?

Cheers

Paul

 

[Ducatiboy stu]

20* is what hydro's are set at. But your sample temp may not allways be that.

I actually knew a glassblower who made hydrometers. They used to calibrate them in salt water tanks 100 at a time

 

[yum beer]

Aside for hydro readings, I'm more concerned about your temps.
26c is way to high to be fermenting at, unless your doing belgians and the like.
If its fluctuating from 12 to 26 during the day some weird shits going to be happening.
Get your temps stable if you can, temp controller and fridge is best, but look into water baths, towels, ice blocks to keep temp closer to 18-20(assuming your doing kits with lit yeast).

 

[bigpaul]

Cheers yum...trying to brew Dutch and Czech pilsner from a tin with the added flavours in the glucose and hops as given to me by my local homebrew shop! When I checked the temperature on the side of my fermenter this morning at 8am it was 16 degrees - right now at 1pm it is 22 degrees...won't get much higher than that if I'm honest!

 

[Ducatiboy stu]

Those stick on the side strip thermos are in no way acurate. They tend to read amb air temp as the plastic ferm insualtes the wort. Better to get a decent thermo and read it from your hydro vessel.

Tear off the strip thermo an bin it.

 

[Dan2]

Thank you...20 degrees it is then! Taking OG & FG readings from out my fermenter, not from kegs that have been gased, assuming that's what you mean?

Cheers

Paul

The yeast produce carbon dioxide as they go to work on (ferment) your wort. This is the gas yum is talking about.
Just put the cap on top of your hydrometer tube (sample in of course, but not hydrometer) and give it a good shake. This should get the CO2 out of solution. The top is likely to blow if it's very gassy - you've been warned.
Before fermentation starts (OG) and once the yeast has finished working (FG) there shouldn't be much gas in solution