Why not achieve strike temp from a mix of boiling and cold water?

So, I've been brewing for some years now, and one part of the process I always wish was more care-free, was getting water to strike temp. Sure if you have some level of automation, this is easy. If you don't you have to essentially watch a pot until your thermometer meets your magic temp. Of course a heated mass of water has a kind of heat inertia, so if you cut your heat as soon as that temp is hit, you will likely overshoot mash temp. I find it needlessly fiddly and annoying, even though these days I nearly always hit my temp.

I was thinking about how German brewers hit mash temps without thermometers, by knowing the volume of boiling water to mix with well water to hit the temp they knew worked. (Or at least that's the fable I've been told)

It seems to me, that if we had a simple calculator, we could determine that if boiling is X, and our tap temp is Y, and we need Z amount of water in the mash, we need whatever volumes of each.

Then on brew day, all you'd need to do it put your quantity of water for the boil in your kettle, and start heating. When you reached boil, you just pour your tap water in the kettle and you're at strike temp. Seems way easier, carefree, and likely more accurate, than watching a needle for a half hour.

Is there any reason we don't do this? If there was a calculator that did this I don't think I'd ever go back to the way I do it now.

Oh and I just did a calculation, the water ratio to get a strike temp of 168, is 8:3, boiling to 65F water.

Firstly, if you use a ratio of 8 parts 212F water to 3 parts 65F water, you will get a strike temp of 172F, not 168.
To get a strike temp of 158F, you would need a ratio of 8:3.4

So assuming I need 13.75 qt strike water, I can measure out 13.75 qt, and put it in the kettle to heat, and check the thermometer, or I can measure 13.75 qt / 11.4 * 8 = 9.65 qt and put it on to boil, and measure 13.75 qt / 11.4 * 3.4 = 4.1 qt of cold water. Incidentally, this does not take into account the thermal mass of the kettle which will be pre-heated to boiling point and which will cause a higher temp than estimated.

Personally, I think I could get better accuracy by measuring 13.75 qt (which I can do easily) and reading the thermometer, than trying to judge 9.65 qt and 4.1 qt (which I cannot do accurately).

-a.

Or you can buy the $20 digital thermo on my site and set the temp alarm to 168F.

I mean, I've used digital thermometers with alarms, but by the time it goes off, you've overshot by a few degrees, an a few degrees more if you were in the next room pulling a pint.

I'm constantly multitasking and overshooting strike temp. Then I have to nanny it back to the right temp before doughing in. The problem is the temp you get from a thermometer is one in flux, unless you regulate the heat until it stays constant for a minute or so.

Boiling, your tap water (or whatever) temp is constant. The thermal mass of the kettle is constant, the temp drop between the kettle and the dough in is (relatively) constant. It just seems that if you know all that you could hit strike temp every time without even trying by taking advantage of the constants. With the right calculator this process is easier than what most of us currently do.

Correct me if I'm wrong but you can easily have water come up higher than the 212 it takes to start boiling. Hitting that exact mark for your calculations to be correct could be just as hard as hitting strike temp. Also I think that adding cold water would produce a lot more steam which would also throw off the calculations a bit

Even still, the hottest your setup can heat will be a relative constant. Once you've done it once, you'll know what that is. Also I imagine the temp inertia will be much less at the edge of your burner's power. Meaning, the closer you are to max heat, the less drift you'd experience. (Theoretically of course).

Not sure about the steam, but still I think whatever difference you'd experience would be relatively constant. Like the kettle's thermal mass.

I'm going to experiment with this I think. At worst it will be as tedious as doing it in the usual way. If results are good, I'll see about making a calculator for it.

Sure you could use a mix of boiling water and cool water in proportion and achieve proper mash temps, but even a cheap digital thermo is easier and more accurate and convenient IMHO. Hell, I have even come to realize that there are visual indications of when or strike water or a mash is at the proper temp. For that matter, just simply mash in low, and slowly heat the mash to carry you threw the proper conversion temperatures and you likely will make fine beer...

It just seems like more trouble than it's worth to try and mix water and hit a temperature.
You're cold water isn't going to be the same every time you brew, your strike water temperature will vary based on the temperature in quantity of grain, and you would have to make sure and have your measurements perfect.
When you go to check the temperature to make sure you hit it, you're going to probably drop it degree or two while you try and stir it up enough to get an accurate reading.
You would wind up with far more variables than just heating the water to strike temperature.

After doing it a few times a guy should know about how long it takes, keep yourself busy and you keep watching the thermometer.

It seems like way more work as others have stated.

You still have to measure the water temperature of the cold water or else your calculation is going to be way off.

Why not just measure the temperature of the strike water? I usually go 2-3F over what they say it should be, so i dump it into my mash tun and stir the hell out of it for 2-3 minutes until it drops down.

killsurfcity said:

I was thinking about how German brewers hit mash temps without thermometers, by knowing the volume of boiling water to mix with well water to hit the temp they knew worked. (Or at least that's the fable I've been told)

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I hadn't heard that fable before. I always heard that before thermometers the brewers would stick the elbow of their arm in the strike water to determine temps.

iaefebs said:

I hadn't heard that fable before. I always heard that before thermometers the brewers would stick the elbow of their arm in the strike water to determine temps.

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I would that there were several methods they used.
I would also bet that with no thermometer their efficiency was all over the place.

Just another example of it would work, you would have beer, but your efficiency and consistency wouldn't be there.

pistachio said:

Correct me if I'm wrong but you can easily have water come up higher than the 212 it takes to start boiling. Hitting that exact mark for your calculations to be correct could be just as hard as hitting strike temp. Also I think that adding cold water would produce a lot more steam which would also throw off the calculations a bit

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Ok, you're wrong! Kidding, but the only way to get (liquid) water over 212 would be to have it above atmospheric pressure.