Step mash water additions calculator

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Dec 29, 2015
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I'm using a cooler, but want to be able to perform step mashes for things like wheat beers. Obviously the plastic cooler rules out heating via the vessel, and it'll be a while until I get around to RIMS?HERMS or similar.

My current solution is to follow the method whereby you add volumes of boiling water to the mash in order to raise the temperature. However, every time you increase the mass of the mash, it takes more heat (and therefore hot liquor) to raise the temperature to the nest rest. A major issue being that if you start with too much liquor, then soon you end up with a very watery mash which won't filter properly and mucks up your OG.

Being pretty wet behind the ears at all this, I have enough to deal with, without having to calculate volumes of water on the hoof. So I've been working on a way of simply calculating the volumes of boiling water needed to raise the mash temperature in a stepped mash. I've found the various formulas required online but they're all from America with the inherent confusion of the imperial system.

I've now converted all the formulas into metric and written them into an Excel spreadsheet, which I'm making available here. At some point I'll probably write them into a stand alone webpage, but that'll have to wait. For now, it'll only work if you have Excel. sorry.

Right, having had a go at uploading it, it seems that an Excel file is not a valid attachment. If you're interested, PM me and I'll e mail you it. Or if anyone has the know-how of how to make it freely available on here, let me know.

I've tested the algorithms with various numbers and crosschecked them by manually putting the numbers through the equations by hand. Everything seems to line up and the resultant volumes make sense. But I can't guarantee that they'll work out perfectly.

So, if you open up the file you'll see this.
mash calculator.jpg

There are three separate calculators. They are all geared up for three rests, so if you're using less, simply fill in the latter ones with the same temp as your last rest and you'll see that the further water additions are 0. All additions are rounded up to 2 decimal places, but this is only what is shown, for convenience. The actual calculations are performed with the full figure, so you don't lose any accuracy. All calculators assume no loses due to evaporation and that your additions are actually at 100°c.

No.1 and 2 are for working out your strike water volume, given a specified set of rest temps and your desired final liquor volume.

No.1 assumes no, or negligible heat loses during the rest periods. This will probably be fine if you use something like a well insulated cooler. Simply input your values for grain weight in Kg, your final volume in litres and your doughing in and rest temps.

No.2 allows for known heat loses in your tun. Input your figures as per the first calculator, but if you know that your tun will drop a certain temp over a given period, work out what that loss will be for your chosen rest period and input those figures in the "temp loss..." column. This is the calculator to use when you've finetuned your system and know the loses for various subtle variables which can't really be covered by these relatively simple equations.

No.3 is for quickly working out the additions as you go along. So you input your volume of strike water and grain weight. Then when you need to raise the temp, measure the temp of the mash and input this as your dough in temp. Input your 1st rest temp and it will tell you the addition you need. At this point the further additions will say weird things Ignore them, it's the equations working out stuff they don't have data for yet. Then when it's time to raise again, remeasure the mash temp and adjust the 1st rest temp to reflect this actual value. Input the 2nd rest temp and it will tell you the next addition volume, and so on.

So feel free to use. Even if they're not perfect, they should get you in the right ball park.

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