Mash tun proportions

[Tom Archer]

A quick newbie question..

I'm currently setting up the wherewithal to make three simultaneous very small British ale brews, so that I can not only test recipes, but also fine tune them. I'm currently looking at a finished batch size for each test brew of just six pints.

As far as possible this will be a faithfully scaled down version of much larger batch production, avoiding temptations like substituting DME or using a BIAB method to save time. Hopefully the results will then later scale up without too much deviation.

Most of the challenges of down-scaling I have a clear plan for, but there's one design element that I'd appreciate advice on.

I plan to use re-engineered Gastronorm pans as miniature mash tuns (I have a large second hand Bain Marie that I can use to keep the mash temperature stable)

These pans come in various sizes, some deep, others broad. The two options I'm looking at are the deep GN 1/6 200mm pan or the broad GN1/3 100mm pan. My plan is to fit a drain and false bottom to each pan to make the mash drain properly.

Designing a sparging arm is less challenging for the deep pan, but the shallow pans would save me re-engineering the Bain Marie.

My question is: What works best when it comes to sparging? Does a relatively deep, narrow grain bed sparge better than a broad, shallow one - or vice versa?

 

[Buffers brewery]

I'd think that while you might scale down the recipe you might consider keeping the "mechanics" the same, i.e. keep the grain bed depth the same in your scaled down kit as you would have in the full size set up. Just a thought.

 

[The-Engineer-That-Brews]

Does a relatively deep, narrow grain bed sparge better than a broad, shallow one - or vice versa?

The quick answer is that a wider, shallower grain-bed is preferred by commercial brewers because you get less temperature gradient from the top to the bottom, and sparging is faster.

In slightly more detail, it rather depends whether you're doing a mash-out, and whether you are doing fly sparging or some other method.
If you're fly sparging then, in general, the deeper the grain-bed the more time you'll have to continue sparging in order to rinse the sticky sugars fully off the surface of the grains. In effect what happens is you get a 'bow wave' of sugars drifting down the temperature gradient - and it has further to travel.

As a side note, scaling down the dimensions of a mash vessel means that the rate of heat loss may be higher because the surface area to volume ratio is proportional to the linear dimension. So with smaller vessels the quality of the insulation becomes much more important.

 

[Tom Archer]

Many thanks for the advice.

It seems reasonable to conclude that the depth of the grain bed is a potential cause of scaling issues, and that it is therefore safer to scale in two dimensions rather than three when considering mash tuns.

Out of curiosity I calculated how big a mash tun would be if scaling up from my six pint test brew using a 1/6 gastronorm to a commercial 10 barrel brew, and concluded (if my sums are correct..) that it would be about ten feet in diameter with the same grain depth - wide, but not unfeasibly so.

Anyway, the gastronorm pans have been ordered.

I now have the interesting challenge of creating a sparging arm. My first thought was to use a fine spray for this, as accurate nozzles with defined spray angles are not hard to source, but the means of pressurising very hot water to food grade standards seems much more elusive. I'll probably settle for a crude gravity feed and perforated bar.

 

[The-Engineer-That-Brews]

Many thanks for the advice.

Welcome
Just remember that with smaller mash tuns you will have to insulate them much better than a normal one (or keep them in something like a water bath to stop heat-loss)

 

[Buffers brewery]

I now have the interesting challenge of creating a sparging arm. My first thought was to use a fine spray for this, as accurate nozzles with defined spray angles are not hard to source, but the means of pressurising very hot water to food grade standards seems much more elusive. I'll probably settle for a crude gravity feed and perforated bar.

I've only seen one commercial mash tun working, so experience is limited, but the water was not "sprayed" on to the malt but just trickled from the sparge arms.

 

[Sadfield]

I think you are over thinking this. Scaling recipes up or down for different kit isn't that complicated if you know the brewhouse efficiency of each system.

 

[Buffers brewery]

Hey @Sadfield wash your mouth out! Complicated is good in my book. The more the better

 

[RoomWithABrew]

I now have the interesting challenge of creating a sparging arm. My first thought was to use a fine spray for this,

For your size batches I'd get a childs watering can!

 

[Sadfield]

Hey @Sadfield wash your mouth out! Complicated is good in my book. The more the better

Sorry. Have you considered fluid flow dynamics? You'll need to address all valves and piping and look at the affect Darcys Law has on varying grain bed depths.

 

[Buffers brewery]

Sorry. Have you considered fluid flow dynamics? You'll need to address all valves and piping and look at the affect Darcys Law has on varying grain bed depths.

That's more like it