Mash Ratio And False Bottoms.

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Crazy Eye's Brewery
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A question for those proficient in all things false bottom. :ph34r:

Every false bottm has a void under it and the one I have just made has about 2 litres although nearly all of this is drainable. So when calculating mash ratio's is there any compensation made for the void under the false bottom.

For example: You are mashing 5kg at 2.5lt/kg with the 2 litre void under the FB- if you just do the simple calculations of 5 x 2.5 you end up with an actual mash viscosity of closer to 2.1 lt/kg casue you lost 2 litres or 0.4l/kg to the void. But if you actually infused the extra 2 litres the calculations would be 2.9lt /kg but the mash viscosity would be closer to that of a 2.5lt/kg infusion in a manifold type mash tun( no void). I realise that there is more to it and it's not a clear cut thing as finer stuff will get washed into the the underside and it fills up and some activity will be happening there. But there must be some general rules to work on.

So what is the go?


Borret :blink:
I have a similar system and I do not add extra water. I have never even thought of it until now. As you said alot of the grain dust still makes it to the bottom, so it is not just water. I have'nt had any problems with the way I do it now, so don't think i would change.


I just mash @ 3 Litres per kg and allow an extra 2 litres to compensate for the FB deadspace. Not rocket science but works well enough. Some mash with less water YMMV.

Just allow the weight of your grain in water absorbtion eg; 5kg grain absorbs about 5 litres of water. With a LG ratio of 3-1, 15 litres + 2 litres for deadspace = 17 litres subtract 5 litres for absorbtion = 12 litres. Sparge with about 13 litres of water + or - a litre to give 25 litres in the boiler and roughly a post boil volume of 23 litres.

You get the point.

:excl: All this is far easier with a refractometer to measure later runnings. You basically hit your target perfectly most times.

Warren -
I just use Beersmith. It works out about 2.5/1 or 3/1 and the rest of the water gets used in the sparge. And thats a good question, i'm glad u asked, yes if you dont do a mashout you could end ep with about 25 litres of sparge water to make up the total boil. So I just sparge until the runnings drop to approx. 1.010. With a nice slow fly sparge often I can run it all thru.


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