OG and pitching ...?

Well I brewed a wheat American today, everything went pretty well but I add question regarding my OG and pitching time ...!!!
I put the wort into a carboy glass 6 Gallons and I was waiting for the temperature to cool done. I took my OG 1st time 1.040 but then I was waiting for the temperature to lower more (this is Miami). When the temperature was around 72F I checked my OG 1 more time and the OG was at 1.030....not sure why the OG changed so I pitched...
Does the temperature of the wort can change the OG? Please help ... Thanks
And if you are in Miami any suggestion for temperature control. Thank you guys

Romeo said:

Does the temperature of the wort can change the OG? Please help ... Thanks
And if you are in Miami any suggestion for temperature control. Thank you guys

Click to expand...

Yes, hydrometers are calibrated at 59F degrees and when taking a gravity reading at anything other than 59F requires an adjustment. Look up hydrometer temperature adjustment charts in Google and you should find a chart to help adjust the reading for your worts temperature. The book How to Brew by John Palmer ( howtobrew.com) has a section on this as well.

As for temp control you can use a swamp cooler, which you can Google also for a better understanding. They are a little messy to deal with but work. I use a cool brewing cooler bag (cool-brewing.com)A very large cooler bag that your fermenter sits it and you manage the temps with frozen bottles of water. It eliminates the water that a swamp cooler uses and contains any blowouts to just the bag. I also live in Florida and this truly has been a beer saver.

I've seen hydrometers calibrated for 60° F and others calibrated for 68° F. Check what yours is calibrated to and definitely google the adjustment calculator dkeller mentioned. I think one of your readings was off though. Gravity goes up as temperature goes down not the other way around.

it could have been that the wort was not mixed well that would explain the difference in readings.
Temperature alone would not account for that large of a swing.

menerdari said:

it could have been that the wort was not mixed well that would explain the difference in readings.
Temperature alone would not account for that large of a swing.

Click to expand...

Thanks for your help

unionrdr said:

The glass one I got with my Cooper's micro brew kit calibrates at 66F. So def look for calibration temp of the particular one you have. Here's a handy hydrometer correction calculator; http://www.brewheads.com/gravcorrect.php

Click to expand...

Sorry for a stupid question but, how do I know about my hydrometer calibration...?
Thanks

unionrdr said:

Mine came in a plastic tube with a smal sheet explaing it.

Click to expand...

Thanks