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-   -   Can yeast in suspension affect gravity reading? (http://www.homebrewtalk.com/f163/can-yeast-suspension-affect-gravity-reading-471494/)

5B-brewing 04-21-2014 04:03 AM

Can yeast in suspension affect gravity reading?
 
Tried searching the forums for an answer to this, but no luck.

Been fermenting a wit for the past two weeks @ 68*. Went to put it in a keg tonight and took a reading. The final gravity should be somewhere around 1.010. My reading came out at 1.020, a full 10 points higher than it should be. Lots of yeast and trub in suspension in the sample. Can this affect the gravity reading?

It is drinking really well and doesn't taste too sweet at all. My wife loved it, even flat and at fermentation temperatures, so I kegged it anyways. It's for a local competition, entries are due by Thursday, so I'm really scrambling at this point. Didn't leave myself a lot of wiggle room. Hoping that is just a faulty reading and not my flaked wheat and oats not converting.

DSorenson 04-21-2014 04:11 AM

Nope! Only dissolved solids effect it.

5B-brewing 04-21-2014 05:30 AM

That's funny, because I have found a few threads since I posted this saying both yes and no.... The wit tastes good so, even though I may not do well in the comp, I'm (trying) not too worried about it.

Beernik 04-21-2014 05:51 AM

I disagree. Floaties can affect your hydrometer.

My most recent experience with this was pulling a sample off a freshly made peach hydromel. I puréed 13lbs of fruit for it. There were so many fruit particles in the sample, the hydrometer read 1.140. I knew it was way off. After filtering it through cheese cloth, it read 1.059, which is what I was expecting.

A little yeast won't affect the reading very much. A really yeasty/trubby sample could have a significant affect

Hello 04-21-2014 08:44 AM

I tend to believe trub can affect the reading as well. Not sure about yeast.

DSorenson 04-22-2014 02:29 AM

Well let me amend my statement. My assumption was that there was significantly more fluid than solids. I took a sample today, for example, from the trub and hop debris left over in my boil from my transfer to my fermenter. My reading was right on with my pre-boil reading and expected results. I used 14 ounces of hops and whirfloc, so that was one trub-y, hop-debris-y sample.

What beernic experienced is a case of too many solids and not enough fluid.

Think of it this way: You can put a rock in the bottom of your sample and still take a correct reading. Fill the sample tube with rocks and you cannot take a reading period, even though there is fluid in there. You will know when you have too many rocks- it will effect the behavior of objects in the fluid.

You should be able to push down on your hydrometer, let it go, and it will float up to a number. Then you also should be able to pick up the hydrometer, release it, and it will float to the same number. Otherwise you have too many solids to take an accurate reading.

I hope this will end all confusion of the subject. You would need collect your sample from the bottom of your fermenter to have enough yeast to impede the motion of the hydrometer. I assume you did not.

GuldTuborg 04-22-2014 03:07 AM

It can, but there would have to be an awful lot in there for it to have much of an effect. I highly doubt extra stuff in suspension like that is going to raise your gravity 10 points. How does it taste?

Any solution, colloid, or liquid with suspended particles can have its density measured with a hydrometer with the appropriate range.

5B-brewing 04-22-2014 03:21 AM

Not carbed yet, but sample was tasty.

I'll pull a new sample tomorrow, let it go flat and see if there is a difference.

DSorenson 04-22-2014 01:51 PM

There may be a difference, and in fact probably will be a difference, if you naturally carbonated.

If you force carb'ed though, you will be fine. Also keep in mind temperature is important. around 60 F is ideal for a reading.


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