Back to Shopping at

Too much rice hulls or too little water or somthing else in imperial stout bad mash

I recently switched from brew in bag to using brewzilla. I have brewed the NB imperial stout a lot in brew in bag and have no problem exceeding the OG using brew in bag. The recipe has 17 pounds of grain to make 5 gallons. I mashed with 8 gallons of water in the brewzilla. I have used the brewzilla several times now. All the other times I adjust the water flowrate so there is a level of water above the grain. This time I had the flow rate as high as pump would go and the level would not build up to above the grain. I mashed for 90 minutes and could not see gravity going up. At end of mash SG 1.055. Had 5.5 gallons in the zilla after draining completed. I sparged then and boiled the heck out of it and got gravity to 1.07 not the 1.086 in recipe. pH during mash 5.5. I noticed I had to add 4 ml of lactic acid to get to 5.5 which I normally do not have to add any for this recipe. Same water chemistry as previous batches. This and the lower gravity seems to indicate poor water grain contacting. All previous batches I got same gravity as I got with brew in bag.

When I previously brewed a double batch of NB Kolsh in the zilla, I started mash with 10.5 gallons and the water level rose to above the grain (18 pounds in double kolsch). Flow rate was not maxed out.

So questions are

  1. is it possible that 2 pounds of rice hulls caused the water to just run down and not distribute across the grain???
  2. Should I have used 10 to 10.5 gallons of water to mash with? This would have resulted in 7 to 7.5 gallons of wort after drain. I could then have skipped sparge and boiled heck out of it to get to 5 or 6 gallons. FYI the zilla has over 2 gallons of water below the false bottom.
  3. Is there something else I should have done? I doughed in but did not spend as much time on dough in as previously. I did use the top plate with holes on it supplied with zilla to spread the water around.

I made 5 gallons 1.07 porter out of a stout :(. Previous brew in bag got 6.1 gallons at 1.083

I’m a BIAB brewer so I’m going to be of little help. About how many pounds do you imagine were above your water line? Does the brewzilla have an internal thermometer and have you verified it’s accuracy?

  1. Get your point on wetting. about 2 out of 10 inch bed depth out of water. 1+.086*.8=1.069 which is about what I got! Good point.
  2. The internal thermometer agrees within 1 degree of my reference thermometer at mash temperatures.

In my experience rice hulls don’t absorb too much water. But, I know rinse them and soak them over night as not every producer rinses them and I have seen some NASTY rinse water while rinsing them. What was your qt:lb?

84/17=1.88 if all the water was being contacted with the grain. But with the combination of false bottom and the tube bottom being higher than the false bottom, its really 54/17=1.17. The bottom of the tube is at 3 >gallons of space below it. I guess this is on the low side of the desired ratio.

I am beginning to think that when I have a high gravity beer that I just forget using the tube and brew with a bag insert but use the pump to circulate wort within the grain. Leaving out the tube will get me at least an additional 1 gallon of contact volume. I will mash it as usual, lift the bag with block and tackle, insert it in the tube to let it drain and sparge(I plan to remove the center overflow tube and plug the center of the tube bottom). It will make cleaning a bit easier as well.

I wish I could buy a false bottom that was a bit lower, as well as a tube that was a bit lower so as not to waste 3 gallons of space.

typo 8*4/17=1.88


My thought… You said you didn’t use a top(?) that disperses the Hot Liquor amongst the grains…
Ultimately… Hot water in contact with ALL the grist makes the efficiency go up… pH also is a factor, yet, you are in the sweet spot… It seems you’ve had some issues in the past with this mouse trap… Can I ask why you ditched BIAB?..

I don’t know if I ditched brew in a bag. I just wanted automatic temperature control to make it easier. As my last post shows, I may sorta go back to BIAB.

1 Like

Duh. I could have done the math- wasn’t thinking. 32qts to 17lbs is ~1.88. Your pH is in line to get conversion. It does surprise me that you needed so much acid for a RIS. But I don’t know your water nor grist.
In a constant recirc setup if your ‘water’ rises during recirc you’re going too fast and sticking your mash. I wouldn’t rely on the recirc to ensure grain is covered. I would add enough water to cover grain then recirc. And figure your water amounts, then add the volume under your false bottom.
I run a RIMS system and add figure out my TOTAL water volume. I add enough water to go 1.5-2” above the grain, then fly sparge with the remaining water.

Loopie thanks for your advice. My water at camp is alkaline. I normally have to use distilled water at 50/50 mix or all distilled and add chemicals back for most brews. The imperial stout normally does not normally need lactic acid addition with all camp water. It did in this one because of poor grain/water contact.

Yeah good advise not to rely on recirculation to cover the grain bed. Trying to add just enough rice hulls to prevent stuck bed while achieving enough pressure drop to ensure head builds up above bed is a tough balancing act. The balance act would likely result in too many stuck beds.

The problem I have is that 3 gallons of water below the grain tube bottom. This is normally not a problem except for the higher alcohol beers. With the imperial stout if I put in enough water to cover the grain bed, I wind up with too much water to boil down to 5-6 gallons. I did some further measurements and there is 1 gallon below the false bottom and 2 gallons below the grain tube but above the false bottom. So I was figuring that I would try biab without the grain tube for the next high alcohol beer/RIS. will still recirculate for temperature control and periodically stir bed like I would normally do for biab. At end of mash will lift it with block and tackle and let it drain. Once drained I will plop the bag in the tube to sparge. I wont get as clear as a wort with this method but will get my my target OG. Might at some point try using the bed as a filter aka the bag as a grain tube. The bag might make clean up a little easier as well.

Thanks again for the advice.

1 Like
Back to Shopping at