Hydrometer Readings

[SJW]

After doing just two part mashes i have noticed a interesting thing that has been happening with my hydrometer readings.
Just after i have cooled the wort and drained into the fermenter and added the top up water and just about to add the yeast, that when i have been taking my OG reading, but for some reason if i do it within abot 10 min's of airating and adding the top up water my hydrometer reading is way of the scale. Like 1100. But if i give it about 20min's it comes back down to where it should be. WHY IS THIS SO? Does it have something to do with there still being a lot of hop material floating around and getting into the Hyrometer test tube? Has anyone else noticed this or am i NUTS :wacko:

 

[Tony M]

Sjw,
I would suggest that the high gravity wort is sitting on the bottom of your fermenter and the water generally resting on top and it would take the 20 min. to mix by convection. you could prove this by giving it a good stir as soon as you have topped up and checking gravity. It needs a damned good stir anyway to aerate.
Sorry SJW, I just read your post again and you said you already aerated, so I have no idea what has caused your problem

 

[RobW]

Micro bubbles from the aeration that make the hydrometer ride high but dissipate after 20 minutes or so? Just a guess.

 

[SJW]

That could be it KenEasy as i sit it in the tub and blast the final 9 or 10 lires in flat out.
So there is no truth to my theory that the hop material has not had time to settle in the fermenter?

 

[RobW]

Combination of the 2?
(obscure Janis Joplin reference)

 

[Trough Lolly]

So there is no truth to my theory that the hop material has not had time to settle in the fermenter?

Hi SJW,
There have been some vigorous debates on this and other forums regarding the influence of solid materials and the gravity of the brew and I don't want to ignite another one, but my reading indicates that the hop matter simply displaces water and will not affect the gravity reading.

You could fit a sinker of lead in the bottom of a glass and still have the same gravity reading, its just that the solid displaces its volume of space in the container - hence the rise in the water level in the glass when you drop in an object.

It is possible that the aeration may assist in floating the hydrometer due to small bubbles attaching themselves to the imperfections in the walls of the hydrometer, especially if the hydrometer is floating in a freshly aerated wort and there is a dense, thick layer of foam that effectively props up the glass tube in the solution before dissipating. The only other reason that I can think of is temperature which obviously varies the gravity of the solution.

Sorry I cannot be more specific than that...
TL

 

[SAMEAGAIN]

Yes I would agree with Trolley lolley also don`t forget to adjust your reading as hydrometers are calerbrated at 20 deg. and I would also say when you took your sample some of the wort you didn`t mix was sitting in the tap hence high gravity.

Regards
Mark

 

[GMK]

I have proved taht TonyM is right.
Did thid the other day - added rain water to the fermenter - did a brix reading from the top.
Stired it up in a vertical motion to mix the bottom with the top - another brix reading and it was higher than before.

Reverse would be true if the sample was taken from the bottom.

 

[big d]

mmmmm
maybe stratiffication.eg heavy at bottom lighter at top.hence hydrometer tends to float abit more than usual if it was a good mix.
only a thought. :blink:

cheers
big d

 

[dreamboat]

Maybe still a slug of more concentrated wort sitting in the tap body which does not get mixed in during the addition of water and aeration. Try draining a hundred mls or so and putting back into the top of the fermenter, then take a reading.


dreamboat