Does trub affect hydrometer reading?

[Rev2010]

Today I re-brewed Northern's Kiwi Express, though I've tweaked out the recipe this time. This time I used a half of Whirlfloc tablet which I hadn't used the last time. Kinda didn't need too since my last one ran pretty darn clear when it was about 50% left in the keg but I figured why not. Now, I strain through a strainer going into my fermenter from the kettle, yet when rehydrating the yeast I noticed the separation in the fermenter, there was a band of trub showing about halfway of the total fermenter level. Obviously this will drop and compact to much less but when I took my hydrometer reading it was full of hop trub and my reading came out high leading to to 87% efficiency. Since getting my new Monster Mill I've been hitting 86% efficiency with my last two beers so today I widened the gap just a little - I really want closer to 81% efficiency as that is what I am so used to having used my Barley Crusher the past 3 years. Anyhow, this puts my IPA at 7.5% alcohol instead of my original estimate of 6.5%.

So, question is, does trub impact the reading? Somehow I would think it does if there's a lot, but then I'd also think any settling would push up the liquid and the hydrometer so it would level out correctly and not lead to a false reading. Anyhow, any input?


Rev.

 

[RandallFlag]

In a word, no. That simple. Unless the hydrometer is resting on a bunch of it, that is.

 

[Rev2010]

In a word, no. That simple. Unless the hydrometer is resting on a bunch of it, that is.

Dang, kind of what I thought. Oh well it will just be a stronger beer. Guess I'll have to widen the gap a bit more.


Rev.

 

[tootal]

Why would you widen the gap? If you're more efficient then change the recipe. You get the same beer with less malt, sounds like a winner. As long as you're not experiencing lautering problems I would leave the mill alone and just readust the recipe.

 

[Menhir]

Hydrometers measure the density of the liquid that they are suspended in. The density is affected by the amount of total dissolved solids (sugars, etc.) as well as the amount of total suspended solids (trub). As an experiment, use a beer thief to grab samples above and below the trub stratification line. I think the sample above the line would be the most accurate reading.

 

[kombat]

Hydrometers measure the density of the liquid that they are suspended in. The density is affected by [...] the amount of total suspended solids (trub).

Is it though? That seems counter-intuitive to me.

Take a hydrometer sample tube and fill it with water. Drop in a hydrometer. It reads 1.000, right? Now, what happens if you sprinkle in some sand? Does the hydrometer read any higher while the sand is sinking through the water to the bottom? No. Does it read any higher once the sand has settled on the bottom? No again. But what if you sprinkle in some simple table sugar? Again, the hydrometer continues to read 1.000 until the sugar dissolves. Then it affects the density of the liquid, and the hydrometer's reading will begin to reflect its presence.

 

[Menhir]

Is it though? That seems counter-intuitive to me.

Take a hydrometer sample tube and fill it with water. Drop in a hydrometer. It reads 1.000, right? Now, what happens if you sprinkle in some sand? Does the hydrometer read any higher while the sand is sinking through the water to the bottom? No. Does it read any higher once the sand has settled on the bottom? No again. But what if you sprinkle in some simple table sugar? Again, the hydrometer continues to read 1.000 until the sugar dissolves. Then it affects the density of the liquid, and the hydrometer's reading will begin to reflect its presence.

If the sand is suspended it will elevate the hydrometer reading. I'm a soil scientist and we use hydrometers to measure the percentage of sand, silt, and clay in soil samples. By taking readings at different time intervals we can calculate the volume of particles that are still suspended. If you want to test this try mixing up some ground up clay or silt with water and measuring it. Clay and silt do not dissolve but are merely suspended. You will find that you will get much higher hydrometer readings.

 

[kombat]

Why would a grain of sand sinking through the liquid raise a hydrometer, while sand sitting at the bottom would not? They're both displacing the same amount of water, but they're not adding to the viscosity of the liquid.

 

[Rev2010]

Why would you widen the gap? If you're more efficient then change the recipe. You get the same beer with less malt, sounds like a winner. As long as you're not experiencing lautering problems I would leave the mill alone and just readust the recipe.

To answer your question, I personally find very high efficiencies lend to some off balancing in the style guidelines - for example the SRM. If I want the ABV to be within guidelines for a high efficiency beer I have to lower the amount of grains used, thereby also lowering the SRM, sometimes to levels below the style guidelines. Also, while I haven't had a single lautering issue I am noticing more flour than usual with the higher efficiency and I've been wondering if that might lead to a little less clearness in my beers. So, I plan to just widen the gap. It's currently at .030" so I'll step it up a little at a time, will try .032" next. I'm guessing the rollers being 20% bigger and one inch longer than the Barley Crusher's is the reason for the increase in efficiency. Plus I have my recipes all formulated for 81% and I really don't want to have to readjust the grains and hops for each one.


Rev.

 

[Menhir]

Why would a grain of sand sinking through the liquid raise a hydrometer, while sand sitting at the bottom would not? They're both displacing the same amount of water, but they're not adding to the viscosity of the liquid.

http://publications.iodp.org/proceedings/308/205/205_4.htm
Simply put, suspended particles will raise hydrometer readings. It's just basic physics. Don't focus on coarse sand particles that settle out very quickly. Instead think about fine particles, like trub, that settle out slowly.

 

[kombat]

Interesting. It seems counter-intuitive, but I guess you learn something new every day! Thanks for the link.

 

[tootal]

To answer your question, I personally find very high efficiencies lend to some off balancing in the style guidelines - for example the SRM. If I want the ABV to be within guidelines for a high efficiency beer I have to lower the amount of grains used, thereby also lowering the SRM, sometimes to levels below the style guidelines. Also, while I haven't had a single lautering issue I am noticing more flour than usual with the higher efficiency and I've been wondering if that might lead to a little less clearness in my beers. So, I plan to just widen the gap. It's currently at .030" so I'll step it up a little at a time, will try .032" next. I'm guessing the rollers being 20% bigger and one inch longer than the Barley Crusher's is the reason for the increase in efficiency. Plus I have my recipes all formulated for 81% and I really don't want to have to readjust the grains and hops for each one.


Rev.

If you're using a 3 roller mill then the first rollers should be at around .069". this cracks the hull and empties it. The second rollers will be set at your final amount. .030-.036. This crushes the endosperm without tearing up the empty hull which just passes on through.

 

[Rev2010]

If you're using a 3 roller mill

Nope, two roller mill. I like the simplicity of a two roller mill and have been doing great with one for 3 years till the knurling wore down so I didn't want to deal with having to deal with a third roller to keep aligned or additionally adjust for different grains.


Rev.

 

[wilserbrewer]

http://publications.iodp.org/proceedings/308/205/205_4.htm

Simply put, suspended particles will raise hydrometer readings. It's just basic physics. Don't focus on coarse sand particles that settle out very quickly. Instead think about fine particles, like trub, that settle out slowly.

Yes, with respect to the science, the obvious reason that the particles settle very slowly is that their density is very close to the surrounding medium, if it wasn't they would float or sink. The suspended trub particles are mostly liquid wort of the same density as the sample aren't they?

Are we splitting hairs here perhaps?

Just seems anything dense enough to sway a reading significantly would settle?

I always thought common practice was that trub does not affect SG significantly? Perhaps I'm mistaken....

 

[Menhir]

I've always pulled my sample from above the separation line so I can't speak from experience as to how much the trub influences the hydrometer reading. I suspect it won't make a big difference but it could be a point or two.

 

[wobdee]

When I pull a hydro sample from my kettle it comes directly from the kettle spigot and always has trub in it. I find as the trub settles to the bottom of the sample tube and clears over an hour or so the reading drops about .001-.002. I go with that reading.

 

[POAS]

I do the same thing that wobdee does. After a while, when the trub settles there is usually a difference in reading of about 0.002 points. So, yes, it does make a difference.

 

[ZebulonBrewer]

Hope no one minds me resurrecting this thread, but I didn't want to start a new one. I have an idea for why this occurs, as it occurred to me, and there is no way I obtained 82% efficiency. Also, to be clear, I'm talking about hop gunk/trub and not the break material that precipitates during chilling.

As people up above stated, the hop trub (likely) doesn't effect the specific gravity of the sample. Simple put, they are solid pieces of matter floating in the liquid, whereas the density we are measuring is of everything in solution: mostly water and many types sugar chains dissolved in the water.

But gravity isn't the only part of the efficiency calculation.

We get the efficiency by looking at the volume of fluid we have. In the way that I brew, I top-up my fermenter to 5.5 gallons at the end of the boil. I also usually run the wort through a colander on the way to the fermenter to get most of the hop gunk. I did not do this for this beer. The beer in question had 6.25 ounces of hops in the boil. My thought is that I actually have a smaller volume or wort in the beer than I usually do (because hops expand like a mofo), and that while gravity is what it reads, my volume is artificially inflated by the solids, making my calculation go higher than it should (82% efficiency when I usually get 72-75%).

Anyone agree with this or know of a way to account for it?

Happy Brewing!

 

[Lahinch]

I recently purchased a big mouth bubbler and put it to use for the first time the other day. Brewed a smoked porter using an extract kit. After transferring the wort to the fermenter I drew a sample from the spigot for a hydro reading. There was a lot of trub, but not so much as to be sitting on the bottom of the tube. It registered a big 1.070. I topped up with some water and took a sample from the middle of the fermenter using a wine thief and it read 1.050. I did this several times with the same variance. The last time I let everything settle for 2 hours before doing the readings and same variance. Despite reading about how trub in the hydro tube does not alter the SG reading, clearly something is causing a much bigger reading when I pull from the bottom of the fermenter vs. the middle. Any thoughts would be appreciated. Thanks!

 

[augiedoggy]

I recently purchased a big mouth bubbler and put it to use for the first time the other day. Brewed a smoked porter using an extract kit. After transferring the wort to the fermenter I drew a sample from the spigot for a hydro reading. There was a lot of trub, but not so much as to be sitting on the bottom of the tube. It registered a big 1.070. I topped up with some water and took a sample from the middle of the fermenter using a wine thief and it read 1.050. I did this several times with the same variance. The last time I let everything settle for 2 hours before doing the readings and same variance. Despite reading about how trub in the hydro tube does not alter the SG reading, clearly something is causing a much bigger reading when I pull from the bottom of the fermenter vs. the middle. Any thoughts would be appreciated. Thanks!

If you reread this whole thread you will see the trub does in fact effect gravity readings... Not sure if you just misread or only read the first few posts...

 

[Lahinch]

Thanks for the reply augiedoggy. I read the thread, but didn't come away thinking there was a consensus. And, those saying the trub does effect the readings seem to imply a small variance (.001 or .002). My variance was .02. I guess going forward I will use a wine thief and draw from the middle as opposed to the spigot and draw from the bottom. I've tried to attach a couple of pictures showing my hydro readings (apologies if they are fuzzy).