Parti-Gyle Porter & Mild

[stitch]

Hi

I'm planning a bit of an experiment tomorrow: a parti-gyle brew, making two beers out of one mash. One brew will be a porter and the other a mild:

I will mash 7.5kg of grains in my 30 litre mash tun at the following percentages:

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75% Pale Malt
 8% Flaked Barley
 8% Amber Malt
 5% Chocolate Malt
 4% Medium Crystal

With 72% efficiency I hope to get 17.5 litres at 1.054 out of the first batch for the porter and 17.5 litres at 1.039 out of the second for the mild. Normally I brew 20-23 litres at a time so if all goes well this is going to be an efficient brew day.

If my estimates of mash output are correct the hopping will be as follows:

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Porter - 37 IBU:
  24g Challenger 60 mins - 22 IBU
  48g Challenger 10 mins - 15 IBU

Mild - 25g Fuggle 60 mins - 15 IBU

Yeast - I will massively over-pitch both with Wyeast 1768 ESB. I'm over-pitching because I have two batches of yeast neither of which I know how many viable cells there are. (One batch is 2 week old rinsed yeast cake and another is stepped up from stored fridge stock.)

Inevitably both brews will be similar but I'm hoping the different strengths and hopping rates will make enough of a difference so they're not boringly so. Anyway, this will be an experiment.

Has anyone else done much of this sort of thing? Any tips?

[barney]

I would do three smaller gyles and take some from one and some from three, and mix all three to get the two strengths, the danger is that the ph of the second gyle will be too high due to the buffering effect of the water. You could always adjust the PH of the sparge Liquid or another solution may be to cap the mash with some roast Barley and have stout instead of mild, a rest with a second batch sparge would probably re acidify the mash.

[stitch]

I think I figured if I kept the water alkalinity down it wouldn't be too much of a problem as the second batch's job is mostly to wash remaining sugars out, rather than doing more conversion.

Funnily enough I did think of chucking some roast barley on top of the mild just to add a bit of flavour and, now you mention it, it would help with pH.

[super_simian]

I would do three smaller gyles and take some from one and some from three, and mix all three to get the two strengths...

Now, that's a proper parti-gyle

[stitch]

Brewday over here. I did end up mixing parts of the gyles together as my estimates for the strengths of the different gyles was way off.