Anvil Foundry 6.5 gallon recipe thickness causing compaction and stuck mashes

Question

I am new to all grain brewing and am using an Anvil Foundry 6.5-gal electric brewing system.

I am trying to use Brewfather's award-winning Mean Brews English Mild recipe (see photos)

As you can see, according to this recipe, requires the following grain bill:

• 5 lbs, 2.2 oz of Maris Otter
• 10.9 oz Crystal 60°L
• 6.4oz Chocolate Malt
• 5.6 oz Caramel 90°L
• 3.5 oz Flaked Oats
• Total grain: 6 lbs, 12.6 oz

The mash-in water volume for this is 4.96 gallons.

On my first attempt I tried using the recommended 4.96 gallons, but with the grain it nearly filled my Anvil to the very top, and the water level was higher than the top of my malt pipe. This allowed the grain to flow over out of the malt pipe and into the area in between the malt pipe and the inner edge of the Foundry. This made it impossible for me to use the recirculation pump and I ultimately had to abandon the boil because I wasn't able to filter the grain off the wort well enough.

So this second time around, I used 3.0 gallons for my mash-in volume and had another 2 gallons heated, treated and ready for sparging (later on). This produced a mash that was far too thick (it was like concrete), so I topped it off with another 0.75 gallons from what that reserved sparge water, and that got me to a decent thickness, but not so much water that it overflowed the top of the malt pipe.

I let the mash sit for 15 minutes, and then hooked up the recirculation kit/pump and began pumping. Within 20 seconds, the pump started groaning, so I turned it off and lifted the lid of the Foundry. All the water that had been sitting in between the malt pipe and the inside of the Foundry was gone (sucked up by the pump) and had been dumped into the top of the malt pipe, and the malt pipe was just on the verge of overflowing (back into the Foundry). I think the mash was still too thick, and when I began pumping, the grain bed compacted inside the malt pipe, created a barrier between the malt pipe's false bottom and the Foundry, and the pump just drained all the water the was outside of the malt pipe.

So I stopped recirculating altogether, kept stirring every 10 mins or so, and at the 1 hour mark did an iodine test. It passed (had good conversion) and I was ready to sparge. I pulled the malt pipe up out of the Foundry, and rested it on the brackets...and it refused to drain. I stirred it really well, scraping the bottom...would not drain. Stuck mash.

I carefully emptied the entire contents of the malt pipe into some sanitized stainless steel cook pots. I ran the malt pipe into the kitchen, cleaned the heck out of it, cleaned the false bottom to perfection, and brought it back to the Foundry. I slowly dumped the cook pots (containing wort + grain) back into the malt pipe...and again it refused to drain. Agin, I stirred it really well, scraping the false bottom...but it would not drain. Stuck mash, again. At this point I was exasperated and bailed on the brew day, for the second time.

Here is my theory on what went wrong:

1. I believe my mash-in water volumes are still way off. This led to the mash being too thick after mash-in.
2. Because the mash was too thick, when I ran the pump, it compacted the grain bed, formed dead space between the malt pipe and inside of the Foundry, and ultimately stuck the mash.
3. Even after I cleaned the false bottom and poured the wort + grain back into the malt pipe, the thickness was still off and so the bed just recompacted and stuck a 2nd time.

So to begin with, how does my theory sound here? Happy to answer any questions if it helps troubleshoot, but I can't really move forward with any solution unless we're confident we have a good theory as to what went wrong on this second brewday. So if anyone has any alternative theories, or sees any red flags, please begin by providing course correction and any steering you are able to!

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Assuming my theory is more or less correct, then it seems to me the root culprit here is a bad grist ratio (mash thickness). If the thickness had been proper, I would have never suffered from a compacted bed and hence, any stuck mashes.

So then, if that is truly the root of the problem, can someone with Anvil Foundry experience help a poor old newbie out? Can someone hold my hand a little bit this first time around and help me tweak both my mash-in and pre-boil volumes, and/or grain bill so that my mash thickness is correct? I'm aiming to be able to pitch somewhere between 3.5 and 4 gallons post-boil. If the grain bill needs to change, my only concern is trying to stay true to the English Mild style (alc %, IBUs, SRM, etc.).

Thanks in advance for any-and-all help!

Answer 1

Congrats on your Foundry, and sorry to hear things haven't gone well on your first couple brews. I have the 10.5 gallon which I bought in 2020 and pretty happy with it. It's a good unit and Blichman/Anvil has been great with their support.

I had numerous stuck mash on reasonable grain bills. I added a couple handfuls of rice hulls and that seemed to help, but the game changer was to get a brew bag. I haven't had a single stuck mash since. I think the holes in the malt pipe just plug up and it's game over. The holes in the brew bag are much smaller so it prevents grain from plugging the pipe. Blichman revised the malt pipe since 2020 but according to this article from 2023, it misses the mark (https://www.morebeer.com/articles/Anvil_Foundry_Mods). A lot of Foundry users just use the bag WITHOUT the malt pipe, but the pipe is kind of handy for lifting the thing out so I like it. Plus it keeps the bag off the bottom of the kettle which seems to make sense for recirculating.

Another trick to draining the mash easier is to raise the temp to 170F after mashing to loosen things up a bit, but this is after mashing so won't help with recirc. Just better for sparging.

The 6.5 Foundry listing on morebeer mentions 2.5-3 gallon batch sizes. The recipe you have listed has a 4.9 gallon batch volume so I wonder if you're simply over capacity for what the 6.5 is capable of?

Maybe cut the recipe in half and see how it goes. I'll bet you'll have much better luck.