When I cook at home I can vary a dish based on what I have in the house or how I feel that day.

The other day I had a recipe that called for peanuts, chipotle pepper, and a specific sweetener.

I didn't have any of them.

So I made it with pumpkin seeds, gochugaru, and molasses and it was amazingly good.

Your average restaurant cook can't do that. Many of their customers return to the restaurant to eat the same dish they loved last time they were there. So the cook has to produce the dish the same way throughout each service and each cook has to produce the dish the same way no matter who's working there.

The same is true for bakers.

People fall in love with your baguette or challah and they want it the same as the last time.

So the baker needs to mix it the same way, let it rise to the same point, handle it consistently, and bake it off at just the right moment.

There are a lot of variables.

One variable that the baker can control is the temperature of the dough after it finishes mixing. This is known as the Desired Dough Temperature.

The room temperature may change, as may the temperature of the flour and other ingredients.

Imagine a cold day where the room, the flour, and the sourdough starter are also a bit cooler.

Then imagine a very warm day where the room, flour, and starter are warmer.

How do we get the dough temperature to be the same when the components are so different?

The answer is that we vary the water temperature.

On a cold day we use warm water and on a warm day we use cold water.

The calculation is fairly easy.

If your dough doesn't use some sort of preferment, you triple the Desired Dough Temperature and subtract the temperature of the room and the flour. You also subtract something called the friction factor. This is the number of degrees that mixing the dough raises the temperature by. The result is your water temperature.

If your dough does use a preferment, you multiply the Desired Dough Temperature by four and substract the temperature of the room, the flour, the preferment, and this friction factor to get the water temperature.

This is not a difficult calculation, but it's one more thing you have to remember, so I've created a simple iOS App that does the calculation for you.

It works in Celsius or Fahrenheit, with preferments and without. Start in settings by setting your friction factor (there are hints on what to start with and how to refine it) and then use the sliders to calculate your water temperature.

Oh, and the app also works on an M1 Mac - which something I didn't discover until I downloaded it from the App Store on my Mac.

Oh, one more "one more thing". If for some reason you don't want to use the app store or want to port it to a different platform you can find the code here on GitHub.