My Second BIAB - The Power of Stirring?

Learning quite a bit from my first BIAB, I was confident this second time around. I made a whole lot less mess, I stressed a whole lot less too. I was too cocky for my own good...

Somehow I got a 1.047 gravity when I was shooting for a 1.074. This was a 10.5 pound (4.76 KG) grain bill in a 3.5 gallon batch. I did Maxi-BIAB style again this time around on my stove, using my little 5 gallon aluminum kettle.

So yeah, somehow my mash was totally off. I had the low gravity even before sparging, so it was my main mash that caused the issue.

Rewind back to my first batch, using nearly the same grain bill, this one gave me around a 1.085 gravity before the sparge was added. So, what did I do different then? The only thing I can think of is that on my first batch, I stirred a lot as I doughed in. On this second batch, I just dumped the entire grain bill in one go, and stirred afterword. When I poured the grist in, it piled up above the head line of the kettle, and I had to push it down as I stirred to get it mixed in. After mashout, I noticed that the top layer of the grain didn't look submerged even though it was submerged after I stirred it.

Am I on the right track here as far as what I did wrong? With such a small kettle, did the lack of stirring cause low extraction? On my first batch with nearly the same grain bill, I poured a little grain, then stirred, then poured a little more, etc. I got pretty good extraction on that first batch, and I think that the stirring allowed the grain to absorb the water better. Thoughts?

Edit: I just thought of a second big variable. I use bottled water because my tap is crap here in Vegas. On my first batch, I used Arrowhead bottled water, which was very basic. I added some PH stabilizer to it to bring it down. On my second batch, I used Albertson's bottled water, which was right on at a 5.4 ph, so I didn't add anything. I have no clue what the actual water profile is for either of these two bottled water products. Could the water have much to do with it?

Thanks in advance,
Dan

P.S. Luckily I had some DME laying around, so the batch should be fine.

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Ralph wrote:Hey Dan, that must be bewildering! I would eliminate as many of the variables as possible, so firstly go back to the water you know works. Also, check all of your measurements of mass and volume, plus check the performance of all the instruments (i.e. hydrometer, refractometer, thermometer, timer etc).
Here's some food for thought: I actually put the grain into the bag first and then lower that into the kettle which is partly- filled with strike water (but reserve a few litres in a jug). Give it a few moments for the grist to soak up some water, then stir well and measure the temp, adjust up or down if need be with some of the reserved strike water. Insulate it well then test it again in 10 minutes after it has stabilised and adjust if need be, however remember that with Maxi-BIAB you want the kettle to be full to the brim during the mash, so manage that reserved water carefully (i.e. boil it if need be or use some cold). After that I don't touch it for at least an hour, I give it a stir just before hoisting the bag, sparge as per the method. I usually get around 80% efficiency with Maxi-BIAB.
Hope this helps!

Thanks a lot for responding, Ralph. Using some top up at the start of the mash to help with dough in was another thing I didn't do on this second batch (I did do that on my first batch though). The grist plus water was definitely filled to the brim. The grains were submerged after I stirred them in, but they didn't look submerged when I checked them after the mash. After I stabilized the temperature at the start of the mash, I didn't open the kettle lid until after the mash was done. My temperature was pretty stable through the entire mash. I didn't calibrate my digital thermometer though, so there is a possibility it was off as well.

So, here's my list for next time:

1. Go back to my old water + PH Stabalizer.
2. Stir while doughing in (or maybe use Ralph's method), and reserve some water for top up.
3. Calibrate my thermometer.
4. Take both a hydrometer reading and a refractometer reading to make sure the refractometer is working right.

I'll post back after my next batch. I am going to do another 10.5 - 11 pound grain bill just because I want to figure this out. So far, based on everyone's input, I am guessing it was the water profile that was the factor. Thanks for all the help, guys.

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PistolPatch wrote:

PistolPatch wrote:And here, I am talking about normal BIAB, not maxi or mini-BIAB. Normal home-brewing is using macro instruments to measure micro results. Mini and maxi-BIAB is using macro equipment to measure electron-microscopic results!

Just quickly dan, I hope no one misinterprets that paragraph which was written in a rush. Mini-BIAB's are a bit harder to measure than normal BIAB's because of the two vessells and smaller volumes. "Electron-microscopic" was an exageration I used to try and quickly say this.

Cheers,
PP

I knew what you meant, and I totally understand what you mean. That is an incentive to get off of Maxi-BIAB, but I'll be doing it for a while due to space limitations. Anyway, thanks again.

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