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Old 06-08-2009, 07:31 PM   #1
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Default Need second opinion on fluid mechanics (siphons)

I brewed a mini-mash last week with three pounds of grain. Used my Igloo 5 gallon cooler with copper manifold (first time using the manifold) and batch sparged. My efficiency was only 71% so I missed my expected O.G. by a couple of points -no big deal, but I have been trying to figure out what's going on and think I may have found the answer. I'd like to see if you guys think this is a reasonable theory.

First, I think the conversion was good - temp was held between 153 and 155, crush was good, pH was OK, sparge water got the grain bed to 166, iodine test indicated total conversion, wort tasted sweet. I think my inefficiency came during lautering, due to dead space in the MLT.

I had previously tested the dead space using only water, and could drain all but about a half cup before the water level dropped to the slots in the manifold and broke the siphon. However, when draining during the mash and sparge, I noticed that there seemed to be quite a bit more water left at the bottom of the grain bed when the siphon broke. During most of the runoff, I had the outlet end of the tube from the MLT at the bottom of the brew kettle, so it would have been beneath the surface of the liquid in the BK, but I did lift it out a couple of times to check the flow rate, particularly toward the end of the runoff. It now occurs to me that that was probably not a good thing to do. I think what happened is that toward the end of the runoff, the flow through the grain was much slower than during my test without grain, even though I had the ball valve wide open. So when I lifted the tube end out of the wort in the BK, the flow rate wasn't sufficient to keep the tube filled, allowing air to enter the siphon from the BK end, something I hadn't even thought about. So the liquid level after the siphon broke could have been as high as the ball valve, leaving as much as 1.5 to 2 quarts (6 to 8 cups) of liquid over and above what was absorbed in the grain, instead of a half cup. Does this sound like a reasonable theory?

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Old 06-08-2009, 07:36 PM   #2
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Do you batch or fly sparge?

71% isnt bad eff. by the way...

Leaving wort in the MLT will affect the eff. somewhat, but you need to also realize that depending on your sparge technique, that last 6-8 cups of wort is VERY dilute.

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Old 06-08-2009, 07:55 PM   #3
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The final running are very low in gravity as POL has stated, so that would be maybe a point or two added, which adds about 1% onto your efficency.

Some quick tips to help you get some higher efficency is to use some 5.2 buffer in the mash. I got a 5% increase when I started using 5.2. make sure that you stir the grains ince you pour in the sparge water. A couple of minutes stirring will help rinse the sugars from the grain, and will help you gain a couple more points. Make sure your volumes are correct. Volume of wort can vary your efficency greatly.

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Old 06-08-2009, 08:24 PM   #4
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I batch sparge (only one sparge). And I think I noticed the excess water when draining the first runnings - may have also had excess water draining the sparge, too, but I don't really remember.

I did use about a half teaspoon of 5.2. Mashed with 2 qt/pound (6 quarts), and late in the mash I added a quart of hot water to keep the temperature up. I sparged with 4.5 quarts. I did stir the grains after adding the sparge water, but maybe not long enough.

I'm not really complaining about the 71% efficiency, but I don't want to make mistakes that lower it unnecessarily - mainly want to see if you think my theory about breaking the siphon from the BK end makes sense.

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Old 06-08-2009, 09:21 PM   #5
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I have no experience with mini mashes. Id say that leaving wort will hurt your eff. To what degree?? Who knows.

I have never seen anyone explore eff. with mini mashes, since the mash provides so little sugar to the overall brew, it doesnt really affect it to a large degree.

What have your eff. been on previous batches?

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Old 06-08-2009, 09:48 PM   #6
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Actually, I don't have any previous efficiencies to judge this against. This is only my fourth batch, third mini-mash, and first with the new manifold. I didn't measure efficiency on the first mini-mash, and think I did it wrong on the second one (I used a braid for those two). The reason I'm worrying about efficiency is that I expect to move to all-grain after doing a few more mini-mashes to perfect my techniques and learn from my mistakes. I know I'll make some more mistakes when I go to all-grain, but I hope they will be different ones.

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