I've been searching online and reading up on all-grains brewing and it seems like most places have indicated that all-grains receipes requires mashing at the full batch size.

Ie. If I want to make a batch size of 23L, I'll have to be mashing the full 23L of water.

Is there any effect if I were to brew less than the batch size amount and top-up water just like how its normall done in kits/partial mash recipes?

1 Answer 1


Yes, you can make a concentrated wort and the dilute that after the boil as with extract.

The key differences are:

  • lower mash efficiency: higher gravity mashes tend to have lower conversion efficiency. To keep boil volume to a minimum, you might even choose not to sparge, and just use the first runnings - expect conversion efficiency around 50%. More grain will be needed compared to doing a full boil.

  • lower hop utilization: with higher boil gravity, you get less bitterness from the hops, so more hops are required.

Apart from those differences, you should get just as good results with a partial boil compared to a full boil.

Just for reference, you don't actually mash the full batch size - typically half of that. The rest of the liquid comes from the sparge.

  • Thanks! What do you mean by higher gravity mashes? Does it mean that having a concentrated wort (less grain-water ratio) creates higher gravity mashes? In that case wouldn't sparging actually help increase the conversion efficiency? Pardon my ignorance, I'm still pretty new to this.
    – David C
    Jun 28, 2013 at 14:48
  • Yes, exactly right higher gravity is a more concentrated wort same amount of sugar but in less volume. Sparging does help increase conversion efficiency, since you rinse more sugar out of the grains, but at the expense of diluting the wort. Whether that's a problem for you depends upon the size of your boil kettle.
    – mdma
    Jun 28, 2013 at 14:53
  • 1
    This is also known as blending. Here's a great article on BYO: <byo.com/component/k2/item/237-blending-for-volume-techniques>
    – Tom McCann
    Jun 28, 2013 at 18:55

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