# Determining the friction factor in baking: calling all bread geeks!

In our earlier blog post on Desired Dough Temperature, we introduced a formula that professional bread bakers use to achieve consistently great results.

We learned that aiming for a desired dough temperature (DDT) in the 75-78°F range will lead to the best flavor and rise in wheat-based yeast breads.

The DDT formula takes into account the principal factors that affect dough temperature — room, flour, preferment (if any), and the friction factor — in order to calculate the one factor the baker can easily adjust: water temperature.

#### Don’t be afraid of a little math

The DDT formula is easy — all it takes is plugging in a few temperature readings, and doing a little multiplication and subtraction.

Even if you avoid math like the plague, I encourage you to give it a try. You’ll be amazed at how much more predictable and consistent your bread baking becomes!

However, there remains one piece of the DDT formula that we didn’t tackle in our previous blog post. What about that pesky friction factor?

While it’s easy enough to check your thermostat or stick a thermometer into your ingredients, determining the friction factor isn’t quite so straightforward.

#### What is the friction factor?

The friction factor (FF) in baking represents the amount of heat transferred to bread dough during mixing and kneading.

Friction can raise the temperature of your dough significantly, so it needs to be taken into account when making dough-temperature calculations.

The tricky part is that the friction factor can change considerably from one mix to the next. This is because so many variables go into mixing and kneading bread dough. Factors like the type of mixer, duration and speed of mixing, and the quantity of dough in the bowl all impact the amount of heat generated.

This can throw unwanted uncertainty into the whole DDT formula. After all, we need a fairly accurate predetermined friction factor in order to calculate the correct water temperature.

Unfortunately, I can’t give you a magical friction factor that will be accurate each and every time you make bread. I can, however, offer some tips on using estimated figures, and also show you how to determine the friction factor for yourself.

#### Choose your own adventure: Is it worth calculating the friction factor?

This is where I recommend you stop and consider how much of a bread geek you are.

Many bakers will be perfectly happy to stick with the friction factor figures I offered in my earlier blog post, and delve no further.

Here are those figures:

•Mixing and kneading in a stand mixer (7-quart KitchenAid mixer using the dough hook on “stir” for 3 minutes, then speed 2 for 4 minutes): FF = 22-24°F.

And here are a few comparison figures:

In his book Bread, Jeffrey Hamelman suggests a friction factor of 24-28°F for most mixers (mixing for 3 minutes on speed 1, and 4 minutes on speed 2).

For hand kneading many bakers go with a friction factor in the 0-4°F range. I do have warm hands and tend to knead quite vigorously, which may explain my higher hand kneading figures.

Given the inherent variability of the friction factor, it makes perfect sense to work with an educated guess. In most cases this will get you close enough to your desired dough temperature, with no further ciphering required.

#### What if you use another type of mixer or a bread machine?

While these figures will work just fine when using a similar kneading process, they won’t be reliable if you change the duration or speed of the mix, or use a different type of machine — like a bread machine or food processor.

This is all the more reason to continue reading so that you can learn to determine the friction factor for yourself.

That being said, bread machines aren’t really set up for use with the DDT formula. This is because they not only create friction, but also intentionally add warmth to the dough production process. Unless you’re willing to eliminate the preheat cycle and use your bread machine only for mixing and kneading your dough, it doesn’t make much sense to worry about the friction factor when using a bread machine.

#### Options for determining the friction factor in baking: for bread geeks only

If you’re a bread geek like me, you’re probably curious about how to go about determining the friction factor for yourself. Maybe you just want to know how it all works, or want to be as precise as possible when it comes to your bread-baking routine.

You basically have two options for determining the friction factor.

#### Option 1: Tweaking

The first option is to adopt an estimated friction factor, and then “tweak” it for your particular mixing and kneading method.

1. Choose a friction factor and then select your desired dough temperature.
2. Use the DDT formula as usual to calculate the water temperature.
3. Mix and knead the dough, and then check the dough temperature.
4. Calculate the difference between your desired dough temperature and your actual dough temperature.
5. Add or subtract this difference from the estimated FF you began with, in order to tweak the FF for the next time you make bread.

#### Option 2: Using the DDT formula to calculate the friction factor

A more precise option for determining the friction factor involves using the DDT formula with a chosen water temperature. In this case, the friction factor becomes the unknown variable.

1. Select the water temperature you’d like to use. Record this temperature, along with the temperature of the room, flour, and preferment (if your recipe calls for one).
2. Mix and knead the dough, noting the duration and speed of your mix method.
3. Take the temperature of the dough after mixing and kneading.
4. Multiply the final dough temperature by the number of pertinent factors (three if there’s no preferment, four if the recipe calls for a preferment), to yield the total temperature factor (TTF).
5. Subtract the actual temperatures of the room, water, flour, and preferment (if any) in order to yield the friction factor.

At this point, even the most diehard bread geeks among you may be wondering how on earth to incorporate such calculations into your baking routine.

Let me show you how I use the DDT formula and the friction factor when I make baguettes.

#### Tweaking the friction factor

It’s a pleasant 70°F in my kitchen and I’m on a mission to make our Classic Baguettes recipe. I mixed the poolish the night before, and it’s now ripe and ready to go.

I decide to adopt a friction factor of 24°F, and use the DDT formula as usual. Both my poolish temperature and my flour temperature are 72°F.

I’m aiming for 77°F as my desired dough temperature.

After mixing and kneading with 70°F water, my actual dough temperature turns out to be 75°F, instead of the 77°F I was aiming for.

This indicates that my chosen FF of 24°F was a bit high, since the increase in temperature is less than expected. To tweak the friction factor, I need to reduce it by the 2-degree difference.

Friction factor = 24° – 2° = 22°F

But what if the dough temperature was 78°F instead of my DDT of 77°F? That’s a sign that the mixer generated more heat than expected. In this case, I’d need to increase my friction factor.

Friction Factor = 24°+ 1° = 25°F

#### Calculating the friction factor using the DDT formula

A few weeks have passed and I’m ready to make baguettes again. This time, I want to calculate the friction factor from scratch.

Summer has arrived in earnest, and my kitchen is a warm 73°F.

First, I have to decide on my water temperature. I use a thermometer to determine my tap water is 67°F, which seems like a reasonable water temperature — especially on a warm summer day.

Next, a quick check reveals that my poolish temperature is 76°F, and the flour is 73°F.

After mixing and kneading, I check my dough temperature: it’s 78°F.

Ta-da! I now have my very own friction factor to use in future baking adventures. Remember, this number will apply best to recipes that are mixed and kneaded in a similar fashion.

In preparation for this blog post, I consulted my old friend Jaydl McCaffrey. She’s one of the talented bread bakers in our King Arthur Flour bakery.

I asked her how she incorporates the DDT formula into her early-morning mixing routine at the bakery.

Jaydl says she does use the DDT formula and a predetermined friction factor (20-25°F) when she mixes a new dough for the first time. However, for her day-to-day mixing she relies on a mixing log.

I much prefer to keep a log of all my data,” she says. “I find this is far more accurate. Some doughs have a large preferment; some a large soaker. Some mix for a short time; some for a longer time on high speed. Using the log and comparing my current day’s data to previous batches helps me narrow in on my choice of water temperature.”

What a great idea for home bakers and professionals alike! Logging all the pertinent data each time you make bread will go a long way toward building consistency in your baking.

Here I’ve logged my results when hand kneading my baguette dough.

Not only will your data provide insight into future baking choices; recording and referring back to previous baking experiences will help develop your knowledge and intuitive baking sense.

#### Tips for determining the friction factor:

1. If you’re math averse, it’s fine to use the friction factors I’ve determined for you: 22-24°F for mixing in your stand mixer, and 6-8°F for hand kneading. If your hand kneading method consists mostly of gentle folds or you have cool hands, go with 0-4°F.
2. You can “tweak” an estimated friction factor for accuracy by subtracting or adding the difference between your desired dough temperature and the actual dough temperature you achieve after mixing.
3. If you want to be more precise, use the DDT formula to determine the friction factor. In this case, the water temperature is known, and the friction factor becomes the missing variable. Take the temperature of the dough after kneading and use this to generate your total temperature factor (TTF). Subtract the temperature of the room, flour, water, and preferment (if any) to find your friction factor.

Hey, bread geeks! I’d love to hear the friction factors you come up with. Consider the comments section one big baking journal; the more data we gather, the more we’ll learn about the mercurial friction factor and how it affects our bread baking.

For some great background on why the friction factor can help make or break your bread, read our blog post on desired dough temperature

Long time professional artisan bread baker, caramel maker and member of our Baker Specialist team, Barb grew up in Ann Arbor, Michigan and has four grown sons. She has baked in Michigan, Maine, Vermont, and Texas (if you count baking cookies for her son's wedding!).

1. Elaine G. King

I’ve never heard of any of this, and I’ve been making my own bread for 60 years. It always comes out fine, because the neighbor who first taught me showed me how the bread should feel when I knead it. That really seems to be all that is necessary for plain white bread and variations thereof. It may be different for all the other things people bake.

1. Barbara Alpern, post author

Hi Elaine, we’re strong believers in doing what works for you, and after baking bread for 60 years I’m sure you could teach us all a few things! These methods can be helpful for those who are having difficulties with their bread baking that may be related to dough temperature, but, as they say, “if it ain’t broke don’t fix it.”
Barb

2. Linda Morgan

How did our Grandmothers and generations before make such good bread? They never thought in these terms.

1. Barbara Alpern, post author

Linda, our grandmothers did most of their kneading by hand, so didn’t need to worry too much about the friction factor, but they probably also learned by trial and error to use cooler liquid on a hot day to protect their dough from rising too quickly.
Barb

1. Barbara Alpern, post author

Hi Karl, a preferment is a type of starter that is composed of a portion of the flour and water from a recipe, plus a little yeast or sourdough starter. Typically this starter is allowed to rise overnight or for 12-16 hours and then added in with the remaining ingredients when the dough is mixed. A sourdough preferment is often called a “levain.” A typical preferment you’ll see in baguette recipes is called a “poolish” and is composed of equal parts flour and water by weight, along with just a little yeast. Pre-fermenting a portion of the flour in a recipe results in deeper flavor development, increases the strength of the dough, and also improves the keeping quality of the bread.
Barb

3. Margo Zwald

What I will remember however it to opt for cooler water on a hot day and also not run my mixer so much.

1. Barbara Alpern, post author

Margo, this is exactly the information I was hoping those who are less enthusiastic about math would take away from this post, so bravo! Using cooler water and paying attention to kneading time came make a big difference in your bread baking in the warmer months!
Barb

4. Judith P. Oppenheim

I am a PhD chemical engineer whose dissertation required a numerical fluid flow equations – and an avid bread baker, a hobby which goes back to my graduate school days. Of course, I love this post – but also feel that I have to add a few comments: the use of the term “friction factor” is not strictly correct; certainly, its reduction to practice in terms of a water temperature requires everything else be held constant: type of bread, recipe, flour composition, mixing bowl temperature (for hand mixing; not as important for mechanical mixing), mixing bowl area and thickness (large vs. small), water quality (dissolved gases, soft vs. hard), and as others have pointed out water-to-flour ratio. These other items are related directly the equations that address the heat capacity of the dough as well as the boundary condition heat transfer between the dough and the mixing bowl interface……..I do go on. For this overworked engineer, I prefer to give my right brain a rest and resort to my intuition when baking bread. Happy Labor Day Holiday to all, J.P. Oppenheim

1. Barbara Alpern, post author

Hi Judith, you had me at “numerical fluid flow equations”! It is, indeed, a flawed formula that can still offer the bread baker some beneficial guidance when it comes to deciding on what water temperature to use. I find having done my own calculations a few times, that my intuition is a little more honed when it comes to what water temperature to use, even if I don’t want to go to the trouble to do all the calculating. Thanks for sharing your expertise!
Barb

2. Dana Johnson

If you were stuck having to predict an end temperature of such a system with no prior data/experience, you would have to account for a lot of different factors as Dr. Oppenheim has listed. One of the great things about empirical processes such as this “factor” is that most of these bits of data dissapear into the background of shared conditions. It is only the variables you normally control for you can have an effect on and provide adjustments for. I very much appreciate Dr. Oppenheim’s reliance on intuition which is one of our most powerful mental faculties. It has often produced the biggest right brain breakthroughs.
To add a bit of trivia, energy gets added to the dough by any deformation that your mixer produces, not just by friction against the bowl. Any time your mixer slows down, that energy is going into the dough, some through friction, and some through bond stressing. Bread making is probably as much a process of forging as mixing, especially for stiffer doughs.

3. Barbara Alpern, post author

This is so interesting, Dana! I love your suggestion that we’re not only mixing, but “forging” bread dough. And I agree that intuition is a great tool, for both bakers and scientists! Thanks for contributing your thoughts to this discussion!
Barb

5. Craig Whitley

This might put me on the high end of the bread geek scale but I put the formula into my master Excel [Google Sheet actually] spread sheet so all I have to do is enter the KNOWN values of Desired Dough Temp, room, flour, FF, pre-ferment, and it spits out the water temperature to achieve that goal. Seems to work well for me.

I have one set up for our KitchenAid and one for hand kneading.

I have also found for the very extremes of low and high hydration breads I need a set of fixed formulas adjusted via observation of the results achieved making those breads because of the smaller or larger amounts of water have a lessor or greater impact on DDT.

1. Barbara Alpern, post author

Craig, you are officially my hero! I’ve often wondered about how hydration plays into the DDT formula and friction, so I’d love to hear your observations related to high and low hydration breads.
Barb

2. Craig Whitley

Barb, this is what I am using which gets me pretty close to altering the water temperature based upon hydration. YMMV.

I first use the formula I learned from KAF which you show in this blog page to determine the water temperature. Works quite well but is somewhat altered by Hydration %, IMO.

I then take that result [Lets call it “TWT” for temp water temp and do the following

“Adjusted for Hydration Water Temp” = TWT-((Hydration%-65)/7)

As the water % increases it has a greater impact on DDT so I started with a base line of 65% hydration because I have not baked anything below that level.

The “7” was a “adjustment factor” which I arrived at from using the supplied formula and witnessing the ACTUAL final dough temp. Placing a 7 in my formula gave me the result I had measured.

Using a hydration % of 75% and an initial Temp Water Temp from your/KAF formula of 76 degrees F would look like this in the formula

76-((75-65)/7) = 74.5 {adjusted Water Temperature based upon hydration %}

This has worked well for me but may go too far into Geek territory.

3. Barbara Alpern, post author

Wow, this is fascinating, Craig! I will definitely have to give your formula a try. Thanks for sharing!
Barb

6. Hope McLaughlin

Does the friction factor affect other doughs (specifically, cookie dough)? My sister swears that her chocolate chip cookies are the best (and they are) because she uses a fork to cream her butter and stir her batter, and not a mixer. Could there possibly be any truth to that theory?

1. Barbara Alpern, post author

Hi Hope, you pose a really interesting question! I’m sure that the heat and action of machine mixing does affect cookie dough in various ways, although these friction factor calculations really only pertain to bread dough. I’m definitely not a cookie expert, but I have to agree with your sister that I find I get better results when I hand mix my oatmeal chocolate chip cookie dough. I always thought it had to do with the mixer incorporating too much air, or manipulating the dough too much. I never really thought about the heat. Probably in most cases the cookie dough wouldn’t be in the mixer long enough to generate a lot of heat, but it’s definitely something worth thinking about on a very hot day!
Barb

7. Alicia

At the risk of adding more geekiness to this discussion, is it possible that the type of flour used, particularly whole grain flours, might affect the friction factor, or is this insignificant compared to the other components of the calculation?

1. Barbara Alpern, post author

We welcome all geeky questions, Alicia! That’s what this blog is all about! You’re totally correct that many other factors can contribute to friction that are not part of this calculation. It may well be that coarser whole grains affect the amount of heat generated. What about recipes that contain a high percentage of soaked whole grains? How are soakers calculated into friction factor calculations? The truth is that determining the friction factor is far from an exact science and there are many, many variables that aren’t accounted for in the DDT formula. Despite the limitations of these calculations, they are still a valuable tool when it comes to controlling dough temperature. Realizing that machine kneading generates a significant amount of heat can help us opt for cooler water on a hot summer day, and that can make a huge difference in the way our bread turns out.
Barb