Moving to larger batch size. Wondering about the effect on efficiency of using a dunk sparge

[dperrigan]

Hi All.

I've been brewing 5 gallon full volume BIAB batches in an 11 gallon kettle for the last year and have been very happy with my efficiency (usually around 80%) and the quality of my beers. Now, with warmer weather on the way I've decided to up my batch size to 7.5 gallons so that I can fill a 5 gallon keg for my keezer as well as a 2.5 gallon keg for outdoor fun.

I've determined that if I hold back 1.5 gallons or so from the mash then I'll have enough headroom in the kettle. I figured that after the usual draining and squeezing of the bag I would dunk it like a teabag in the remaining water and add that to the kettle as it's coming to a boil.

Has anyone had any experience using both methods? I'm wondering how this will affect efficiency, so that I can calculate my mashbill as accurately as possible. I'm also wondering whether there is anything else to consider that I may have missed.

Any help would be appreciated.

Thanks!
Dan

 

[CascadesBrewer]

Has anyone had any experience using both methods? I'm wondering how this will affect efficiency, so that I can calculate my mashbill as accurately as possible. I'm also wondering whether there is anything else to consider that I may have missed.

When I started with BIAB I did a dunk sparge for my first few batches and I will do a dunk sparge with larger gravity beers. I don't have hard data on the same recipe, but I typically saw an overall efficiency jump to 80% to 85% from my baseline of 75% with a full volume mash. With my high OG beers, the dunk sparge keeps me at near that same 75%, where I am sure it would be lower with a full volume mash.

I would say that factoring in a 5% boost would get you close.

I have not 100% figured out my water treatment strategy when I dunk sparge. I have tended to treat just the mash water (with salt and acid adjustments) and used tap water (treated for chloramine) for the sparge.

I have been thinking about a similar approach so I could full a 5 gallon keg and a 2.5 gallon keg from one batch using a 10 gallon kettle.

 

[DBhomebrew]

Given a constant pre-boil volume, you'll find ~8% boost in mash efficiency going from no-sparge to a single dunk sparge. Best efficiency is found when the first runnings are fully drained before the dunk. Be sure to fully mix the sparge water into the grain ball. Open the bag, mix it up. Don't just dip it like a tea bag. Also, for best efficiency, try to make each runoff roughly equal to each other.

Most importantly, try to do things in a repeatable fashion. Repeatable means predictable.

 

[DBhomebrew]

I treat my mash water with Ca salts and acid as needed to hit mash pH. More Ca salts and NaCl go straight into the kettle to hit my chosen overall mineral profile.

 

[dperrigan]

Thanks for the advice. This is going to be fun.

 

[tracer bullet]

My experience for #'s is similar. Low to mid 70% without sparge, low to mid 80% with sparge. I dunk sparge (grain bag is squeezed and then moved to another pot).

You could consider your first batch on a recipe where you dont' care very much about the gravity and ABV. SInce you're already in the 80's maybe plug just 5% into your recipe and give it a whirl.

 

[doug293cz]

Given a constant pre-boil volume, you'll find ~8% boost in mash efficiency going from no-sparge to a single dunk sparge. Best efficiency is found when the first runnings are fully drained before the dunk. Be sure to fully mix the sparge water into the grain ball. Open the bag, mix it up. Don't just dip it like a tea bag. Also, for best efficiency, try to make each runoff roughly equal to each other.

Most importantly, try to do things in a repeatable fashion. Repeatable means predictable.

The above is a good, and correct, summary.

It is relatively straight forward to calculate lauter efficiency for batch and no-sparge processes. Mash efficiency is conversion efficiency times lauter efficiency. You can measure conversion efficiency using the method here, and if you have a consistent process, your conversion efficiency should be the same batch to batch. So, if you know your conversion efficiency, you can predict your mash efficiency for any combination of grain weights, water volumes, and sparge process (as well as a few other variables.) Here is a spreadsheet that does just that. The calculations assume that the apparent grain absorption rate is the same for all draining steps, so for good accuracy, any sparge needs to be drained/squeezed the same as the original run-off.

The chart below shows the results of simulations for four different sparge counts, two different grain absorption rates, and a range of grain bill weight to pre-boil volume ratios.

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