Help with decoction

[Ticebain]

Just did my first decoction today. Beer is going to be great and talk about high efficiency!

But I did have some hiccups. I brewed an alt and had 9.5 pounds of grain. My mash thickness was 1.68/1. I followed kaiser's formulas from his excellent decoction video exactly and did an enhanced double decoction just like he does in the video. I mashed in at acid rest and brought the first 12 qt decoction (according to the formula that was what I needed) to protein and sac rest before boiling. Then I combined mash and decoction to get mash to protein rest and then to sac rest. Then pulled an additional 5 qt decoction (again according to formula) and boiled then combined again for mash out

I did have some problems though. My decoction did not hold enough heat to get to the right temps. I work on a stove though, so I just turned the burner on and stirred like nuts for a few mins til I hit the right rest temp, but for both main mash sac rest and mash out I was off by about 10 degrees. I even increased kaisers formulas by 20% as he suggests. Anyone know why?

Here's the details
9.5lbs grain
1.68 qts/lb mash water
Doughed in to an acid rest temp of 97
Protein rest at 133
Sac rest at 156
Mash out at 168
First decoction 12 qt
Second decoction 5 qt

I know the obvious answer is that my decoctions were not big enough but where was my calculation off?

Also. My first decoction was super thick and even getting 12 qts was pretty tough. I was dragging the bottom of the mash tun pretty heavy to get all 12. So if I needed a bigger decoction do I just need to add liquid?

Thanks

 

[Cyclman]

Do you hold temps well otherwise? If so, then it's the decoction. I did my decoctions outside, and typically have to direct fire my MLT to keep temps for an hour, so didn't notice a difference.

Decoctions are fun, yes?

 

[Ticebain]

Yes I did hold my temps. I added a little heat in each rest by the stove burner to maintain the temps. Which was what was so confusing since it was way off (10 degrees)

And yes. They are fun

 

[Yooper]

A larger decoction can be tough to stir, as you should have almost all grain in it, with just enough liquid to be able to boil the grain. That's because you don't want to denature your enzymes.

When you do the mash out decoction, you can pull a decoction that is mostly liquid, as that's when you do want do denature the enzymes, so maybe that would have helped with that last decoction holding temperature.