Author Topic: Does yeast in suspension effect hydrometer reading  (Read 2481 times)

Offline charlie

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Re: Does yeast in suspension effect hydrometer reading
« Reply #60 on: February 11, 2018, 12:48:58 AM »
On this thread, just for kicks, let's try to prove our assumptions, or disprove them. So far all I am saying is that suspended solids (yeast) effect a hydrometer reading. It appears that the amount of effect is in relationship to the amount of suspended solids.

Where I'm headed with this. Is using a hydrometer really the benchmark when determining final gravity in a finishing/finished beer? Is it reliably more accurate than the average correction factor / refractometer software/spreadsheet/Apps?

I have wondered about this for a while. Couple'a thoughts:

1. I'm guessing that the density of yeast cells is about 0.8, so suspended yeast should effectively decrease the density of the solute allowing the hydrometer to sink further and give a false low reading. Instead of using dry yeast how about we use yeast recovered from the fermentor? Three samples.
A. Tap water.
B. Tap water plus 10 gm of yeast slurry.
C. Tap water plus 100 gm of yeast slurry.

2. In my experience refractometers are student instruments at best. Using my nice expensive (I forget which model) refractometer I was unable to reproduce a single result, so I traded it to an optimist for a beer filter (which is now for sale. lol)

You can eliminate the dissolved solids concern in a finished beer by refrigerating the sample for 6-8 hours. The yeast will lay down and play nice, and you get a nice clear sample.

Note: When I worked at the brewery I had to use Plato saccharometers, and I came to love them. So now I take all my readings in degrees Plato and translate the reading to SG (because I don't think in Plato).

Charlie
Yes officer, I know that I smell like beer. I'm not drinking it, I'm wearing it!

Offline hopfenundmalz

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Re: Does yeast in suspension effect hydrometer reading
« Reply #61 on: February 11, 2018, 01:15:42 AM »
Jim might like this.

On our Grand Canyon trip our guide said she would look for the toungues of water in the rapids and avoid where it was churned up. “You don’t float on foam!”
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Offline Robert

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Re: Does yeast in suspension effect hydrometer reading
« Reply #62 on: February 11, 2018, 01:27:00 AM »
Jim might like this.

On our Grand Canyon trip our guide said she would look for the toungues of water in the rapids and avoid where it was churned up. “You don’t float on foam!”

She might have been right, but irrelevant to our topic, if she was looking out for water circulating between surface and bottom. The issue there is a down current, I think: a mini waterfall. Rising bubbles will lift a floating object regardless of the AVERAGE density of poolwater and poodles, as it were.  They are exerting an upward force.  One of the more amusing demonstrations of this somewhat counterintuitive fact was an old Mythbusters episode questioning whether a swimmer would sink in an upsurge of bubbles from an undersea release of gases, because of reduced density (they will not.)  The first bench test involved, you guessed it, a hydrometer in a jar with rising bubbles.  Up goes the hydro.
Rob Stein
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Offline charlie

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Re: Does yeast in suspension effect hydrometer reading
« Reply #63 on: February 11, 2018, 01:34:12 AM »
She might have been right, but irrelevant to our topic, if she was looking out for water circulating between surface and bottom. The issue there is a down current, I think: a mini waterfall. Rising bubbles will lift a floating object regardless of the AVERAGE density of poolwater and poodles, as it were.  They are exerting an upward force.  One of the more amusing demonstrations of this somewhat counterintuitive fact was an old Mythbusters episode questioning whether a swimmer would sink in an upsurge of bubbles from an undersea release of gases, because of reduced density (they will not.)  The first bench test involved, you guessed it, a hydrometer in a jar with rising bubbles.  Up goes the hydro.

Yes, but the principle is the same: A suspended something with less density than the liquid!

Charlie
Yes officer, I know that I smell like beer. I'm not drinking it, I'm wearing it!

Offline Robert

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Re: Does yeast in suspension effect hydrometer reading
« Reply #64 on: February 11, 2018, 01:41:16 AM »
Yep.  Particles and bubbles will both lift a hydrometer.  A refractometer will not be affected by either unless the yeast is so dense that the effect of diffusion makes it impossible to read.  The gas is expelled when you close down the cover plate.
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline klickitat jim

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Re: Does yeast in suspension effect hydrometer reading
« Reply #65 on: February 11, 2018, 01:47:58 AM »
Jim might like this.

On our Grand Canyon trip our guide said she would look for the toungues of water in the rapids and avoid where it was churned up. “You don’t float on foam!”
Yup. Generally, the middle of the river is the safest.

Offline Robert

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Re: Does yeast in suspension effect hydrometer reading
« Reply #66 on: February 11, 2018, 01:58:23 AM »
On this thread, just for kicks, let's try to prove our assumptions, or disprove them. So far all I am saying is that suspended solids (yeast) effect a hydrometer reading. It appears that the amount of effect is in relationship to the amount of suspended solids.

Where I'm headed with this. Is using a hydrometer really the benchmark when determining final gravity in a finishing/finished beer? Is it reliably more accurate than the average correction factor / refractometer software/spreadsheet/Apps?

I have wondered about this for a while. Couple'a thoughts:

1. I'm guessing that the density of yeast cells is about 0.8, so suspended yeast should effectively decrease the density of the solute allowing the hydrometer to sink further and give a false low reading. Instead of using dry yeast how about we use yeast recovered from the fermentor? Three samples.
A. Tap water.
B. Tap water plus 10 gm of yeast slurry.
C. Tap water plus 100 gm of yeast slurry.

2. In my experience refractometers are student instruments at best. Using my nice expensive (I forget which model) refractometer I was unable to reproduce a single result, so I traded it to an optimist for a beer filter (which is now for sale. lol)

You can eliminate the dissolved solids concern in a finished beer by refrigerating the sample for 6-8 hours. The yeast will lay down and play nice, and you get a nice clear sample.

Note: When I worked at the brewery I had to use Plato saccharometers, and I came to love them. So now I take all my readings in degrees Plato and translate the reading to SG (because I don't think in Plato).

Charlie

Couple of things, Charlie.  First I missed an opportunity to do your test:  Right before I read back in this thread and saw this post, I pitched today's brew --  and dumped out the rest of my jar of rinsed harvested yeast! Maybe next time.  Second, were those Plato saccharometers top reading? That at least eliminates the problem of seeing through a yeasty sample if not the problem we're addressing.  (BTW, one reason I'm happily going back to a refractometer is that I DO think in Plato, I used to convert sg!)
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline klickitat jim

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Re: Does yeast in suspension effect hydrometer reading
« Reply #67 on: February 11, 2018, 02:02:43 AM »
As I crack my second Siera Nevada Experimental Hop IIPA, following a.... day, I thought I would share this parting wisdom on hydrometers.