The real reason married men should fly sparge?

[HantsGaz]

Hit submit too early - can understand why that confused you! Have updated the post!

[HantsGaz]

Here's another thought / question for you, Chris - that might point me in the right direction....

If you were to collect 31 litres from 4.12kg of pale malt what would your expected pre-boil gravity be? If it's different to mine, then this is the area I need to examine more closely. As mentioned above, I'd estimate 1.030 based on a 75% efficiency, here's my calculation:

Grist 4.12 (kg) * 301 (extract kg/L) / 31L (boil volume) x 75% (efficiency) = 1.030 pre boil gravity

[HantsGaz]

Graham's recipes (to the best of my knowlege) are based on the efficiency in the fermenter, or over all efficency so they take into account all the losses. When efficiency is mentioned it is generally considered to refer to your final, over all efficiency as this is what effects how you design your recipe.

In otherwords, if you can achieve an overall efficiency of 75% you will hit the target gravity at required volume in the fermenter. This includes achieveing a lower volume at a higher gravity which when let down to the final volume is reduced to the target gravity.

That might just be it - I'm using mash efficiency, not overall efficiency (in my calcs) ...... How do you calculate overall efficiency?

[HantsGaz]

Bingo . So, the reason why I have to increase my grain bill to hit the target gravities is because my overall efficiency is in the low 60%'s. Thanks - I think that sorts this out now.... Thanks loads.

[Chiltern Brewer]

Another question about fly sparging anyone?

I have always fly sparged. And when I was first taught how to do it, I was always under the understanding that the grain bed was to be moist, but not underwater. To float the grain bed seems almost against everything I was taught. Surely if it floats, the path of least resistance becomes the edges of the tun? Surely it should be compacted enough to not crark but not under an inch of water. Most people on here seem to have there sparge water as nearly as deep as a batch sparge.

Which is right, which is more efficient?

Cheers,
Matt

It is something that was explained very well in an article on mash systems by David Edge and the Midlands Craft Brewers (unfortunately I can't find it on the CBA website anymore)... that the grains of an single infusion mash tend to float up through the sparge liquor. We're not talking about flooding the mash tun, the grains are floating just above the false bottom/manifold and there doesn't have to be any standing water on top for this to happen. If you run off too quickly the grain bed will drop and you may get a stuck mash as a result. Ideally you are trying to match the in and out flows, and personally I try to avoid flooding the top of the grain bed.