#### IainM

##### Syphon-sucking bag squeezer

So,

T_pitch is the pitching temperature you want, in Celsius.

T_ice is the temperature of your freezer, in Celsius.

V_ice is the volume of water in the bottle you froze, in litres.

V_bulk is the volume of wort to which you are going to add the ice, in litres.

T_add is the temperature you need to cool down to before putting the ice in, in Celsius.

The equation, then is:

To give an example, image you want to get 18 litres of lager wort at a pitching temperature of 10C, by adding a frozen 2L bottle of water from freezer (at -5C) to 16L of wort of more concentrated wort. In this case Tpitch = 10, Tice = -3, Vbulk = 16 and Vice = 2. Putting these in gives you Tadd = 10 + 0.031 * (6.18 + 41.8 + 333.6) = 21.8. So, you can chill your wort down to 21.8C, put in the 2L of frozen water, give it a stir to melt it, and you end up with 18 litres of wort at 10C, ready to pitch and ferment. I've tried this out a couple of times, and it works very well. In practice, this is all you need to know, but in the next post I'll put a bit of theory for those that might be curious as to why the equation works, and why it is the way it is.