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 Home Brew Forums > BIAB Brewing (with pics)
10-26-2011, 06:51 AM   #381
The_Dog_42
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Quote:
 Originally Posted by thughes Good question....I have no idea if that will affect gravity. 1) I am not a chemist or an engineer. 2) I use a refractometer to measure gravity. I tend to subscribe to the explanation provided by somebody here: "The density of the water in the pond is not affected by the number of fish swimming, logs floating, and weeds growing in said pond. Makes sense to me!
That is certainly a tough question to answer. My gut reaction is that if the insoluble fiber is in solution, then the gravity would be affected. I'll try to explain using the above example, but I'll probably do it poorly.

Let's say you want to know the density of pond water, including all things floating in it (fish, logs, weeds, etc.). Your sample when you put (a really large) hydrometer into it would have to include enough water to have an adequate amount of fish, logs, and weeds. Because the fish and logs and such displace a different volume of water than...water, they affect the gravity. Basically, because they are a different density than water, the "gravity" of the solution is not going to equal 1.000.

So to come back to beer, if the fish are dissolved sugars, the logs are the insoluble fibers and the weeds are the hop particulates. All of these particles will change the density of the hydrometer sample, because they are not the same density of the water. So the particles change the specific gravity. The only other comment I can make is a refractometer and a hydrometer should read the same SG because (I assume that) light refracts off the fiber particulates the same as it refracts off the sugars, or at least the refraction is close enough that you couldn't discern a difference without a computer and/or laser.
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 Originally Posted by TANSTAAFB My 10 yr old chocolate lab Guinness :D thinks her name is goddammit dog or fu@%in' puppy...I think if she were registerable :drunk: her full name would Goddammit Guinness Stop It...Go Away!!! And we Love her dearly :)
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10-26-2011, 12:00 PM   #382
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Good answer. That's what I think, too. What I wonder is how to set my new Barley Crusher to provide maximum brewhouse efficiency without generating falsely elevated readings. This might need a thread of its own.

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10-26-2011, 02:41 PM   #383
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I think it all depends on whether the matter is soluble or insoluble. If it's dissolved (sugar molecules), then it affects gravity. If it's insoluble trub that has precipitated, I don't believe it will affect gravity reading at all. Just my two pennies.

I wouldn't jump to changing your barley crusher settings. Why not setup a simple experiment next time you brew? Grab a sample in a normal fashion (will eventually precipitate trub at bottom). At the same time squirt a larger volume into a second vessel. Allow the trub to separate while the 2 samples cool. Making sure the sample temps are identical, very carefully grab a sample from the 2nd vessel so that no trub or insoluble particles are picked up. Measure that sample and compare. I would bet you get identical results.

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10-26-2011, 03:02 PM   #384
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Good point on insoluble vs. soluble material.

Another interesting point on this is that the fiber is a starch. The amylase rest (151F-160F) would also break down some, if not all, of the soluble fibers in the conversion of starch to sugar. So it's possible that we have more trub through the process, but that the final gravity readings are not skewed by fiberous material (like the post above said). If that is the situation, then you'd only have the long and short chain sugars to the SG reading you're taking. As with a normal AG process, the long chain wouldn't break down but would provide body (mouth-feel) and some sweetness to the beer and the short chain sugars would get broken down by the yeast.

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 Originally Posted by TANSTAAFB My 10 yr old chocolate lab Guinness :D thinks her name is goddammit dog or fu@%in' puppy...I think if she were registerable :drunk: her full name would Goddammit Guinness Stop It...Go Away!!! And we Love her dearly :)
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10-27-2011, 03:30 AM   #385
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Might be a dumb question but...I bought the AHS Fat Tire clone all-grain kit to try my hand at BIAB (and this will be my first all-grain too). Will using the grain bill that came with the kit work well with BIAB or would I need to up the grains a little?

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10-27-2011, 03:45 AM   #386
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Quote:
 Originally Posted by h22lude Might be a dumb question but...I bought the AHS Fat Tire clone all-grain kit to try my hand at BIAB (and this will be my first all-grain too). Will using the grain bill that came with the kit work well with BIAB or would I need to up the grains a little?
If you are just starting out with BIAB I would suggest increasing the base malt by a pound or two. After a few batches you shouldn't need the extra grain once you get your equipment and process well dialed in.
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10-27-2011, 01:29 PM   #387
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Thanks for all of the answers.

It's my understanding that efficiency is measured before the boil when the insoluble particles are still in suspension. If I were to design an experiment I would keep two post-mashout samples. One sample would be measured immediately and one would be kept at temperature until the insoluble particles precipitated the measure SG and compare. To be sure, this should be done with a variety of recipes, crushes and conditions.

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10-27-2011, 03:12 PM   #388
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Quote:
 Originally Posted by h22lude Might be a dumb question but...I bought the AHS Fat Tire clone all-grain kit to try my hand at BIAB (and this will be my first all-grain too). Will using the grain bill that came with the kit work well with BIAB or would I need to up the grains a little?
I use AHS kits all the time. Last time I had them double crush the grains and I hit my numbers spot on, so if they haven't shipped yet, I'd see if they can crush twice.

Quote:
 Originally Posted by Strangelove Thanks for all of the answers. It's my understanding that efficiency is measured before the boil when the insoluble particles are still in suspension. If I were to design an experiment I would keep two post-mashout samples. One sample would be measured immediately and one would be kept at temperature until the insoluble particles precipitated the measure SG and compare. To be sure, this should be done with a variety of recipes, crushes and conditions.
Good idea. Probably need to start a new thread on this one though.
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 Originally Posted by TANSTAAFB My 10 yr old chocolate lab Guinness :D thinks her name is goddammit dog or fu@%in' puppy...I think if she were registerable :drunk: her full name would Goddammit Guinness Stop It...Go Away!!! And we Love her dearly :)
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10-27-2011, 03:19 PM   #389
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I'd have a little bit of extract on hand to make up any shortfall you may have. To be honest there's no real reason for it, efficiency on my first attempt was 78%.

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10-27-2011, 03:37 PM   #390
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Quote:
 Originally Posted by h22lude Might be a dumb question but...I bought the AHS Fat Tire clone all-grain kit to try my hand at BIAB (and this will be my first all-grain too). Will using the grain bill that came with the kit work well with BIAB or would I need to up the grains a little?
I have done several AHS BIAB and they all come out great. I dont up the amount of grain at all. You will be fine.
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