FG drop after clarifying?

[foxtrot]

Has anyone noticed a drop in FG after clarifying (either by using clarifying agents or chilling)? If so, by how much?

I would think that the suspended yeast / proteins or whatever would contribute to the gravity reading. So the TRUE FG isn't until the beer falls clear.

Thoughts???

 

[Orfy]

Nope,

Only dissolved matter adds to the gravity if the hydrometer can free float.
Suspended particulates do not.

 

[david_42]

If the suspended particles varied more than a tiny amount from the liquid, they wouldn't be suspended for very long. Since an ale takes weeks to clear ...

 

[Got Trub?]

The hydrometer measures the specific gravity of the fluid. The SG is determined by the solvent (in this case water) and whatever is dissolved in it (sugars, salts etc). Suspended material will have no effect. If your SG is falling after clarifying it is because it was still fermenting...

 

[ajf]

Perhaps SWMBO was sampling the brew and topping up with water thinking you won't notice.

-a.

 

[foxtrot]

Actually, SWMBO DOES like the taste of my hydro samples... I should locking my fermenting room...

OK, I get the points made earlier about suspended particles; here's another angle - what about the effect of dissolved CO2 on FG (prior to carbonating)? Someone mentioned in a LHBS that the FG can be affected by this. Seems to me there wouldn't be much dissolved CO2 with a airlock on the whole time.

Hopefully these questions aren't too elementary; I just haven't come across anything addressing this topic and want a better understanding of my FG hydrometer readings.

 

[Orfy]

As said above.

If it's dropping then it's because it's still fermenting. Quite common for a "Finished" brew to kick start on agitation or change of temp.

 

[nabs478]

The hydrometer measures the specific gravity of the fluid. The SG is determined by the solvent (in this case water) and whatever is dissolved in it (sugars, salts etc). Suspended material will have no effect. If your SG is falling after clarifying it is because it was still fermenting...

That is not correct, anything that is suspended and floating, even semi uniformly, in solution will have an effect. The bouyant force is equal to the weight of the fluid displaced, if that fluid has other carp in it, then it will have an effect.

For example, has anyone seen that mythbusters when they make quick sand? A person floats with about half their body sticking out of the quick sand as it is being agitated because the sand/water mixture is roughly twice the density of water on its own. But the sand is definately not dissolved in the water.

 

[Orfy]

That's because the particles are stopping the hydrometer free floating because of the amount of them. (more by volume then the water)

The water is all (mostly) absorbed by the matter.

Like I said, it depends if the hydrometer can free float in the liquid.

 

[Got Trub?]

That is not correct, anything that is suspended and floating, even semi uniformly, in solution will have an effect. The bouyant force is equal to the weight of the fluid displaced, if that fluid has other carp in it, then it will have an effect.

For example, has anyone seen that mythbusters when they make quick sand? A person floats with about half their body sticking out of the quick sand as it is being agitated because the sand/water mixture is roughly twice the density of water on its own. But the sand is definately not dissolved in the water.

That is because the mixture is agitated and the particles (sand) are not allowed to settle out. In your wort sample after a few minutes anything that is still suspended will be so because it has a similar density to your wort.