Need a formula, if possible

[Link]

I'm kinda math challenged, can someone help with this.

Lets say I have 26oz of sourdough starter mixed at 145% hydration

16oz of water
11oz of flour

now I want to use x ounces of starter (lets say 10oz this time), then add enough flour to take hydration down to 65%. x depends on size/quantity of end product

Is there an easy formula to calculate how much flour I need to add.

Thanks, Link

[Pete-zza]

Link,

The 10 ounces (x) of your starter will have the same hydration as your 27 ounces of starter, that is, 145%. By definition, the amount of water (w) in your x ounces of starter will be 1.45 times the amount of flour (f) in your x ounces of starter. That is, w = 1.45f. Doing a bit of simple math, it turns out that the amount of flour (f) is equal to x divided by 2.45. That is, f = x/2.45. So, if x equals 10 ounces, the amount of flour is 10/2.45 oz., or 4.08 ounces. The amount of water is 1.45 times that amount, or 5.92 ounces (you can alternatively subtract the 4.08 ounces from 10 ounces). If you divide the 5.92 ounces of water by the 4.08 ounces of flour, you will see that the ratio comes to 145%.

Now, to add more flour to the 10 ounces of starter to get the total to a hydration of 65%, you would use the expression w/(f + f1) = 0.65, where f1 is the additional flour you will have to add to the 10 ounces of starter to get to a hydration of 65%. The amount of flour f1 needed can be expressed as

                                       f1 = (w-0.65 f)/0.65

So, plugging in w = 5.92 ounces and f = 4.08 ounces in the above expression, solving for f1 will give you a value of 5.03 ounces of flour that you will have to add to your 10 ounces of starter to get to a final hydration of 65%. If you divide 5.92 ounces of water by the total flour (4.08 plus 5.03, or 9.11 ounces) you will get 65%.

So, to use the above expression for f1, you will first have to solve for w and f based on the quantity x and the hydration percent of your starter.

Peter

[November]

Or you could just enter the numbers into the Mixed Mass Percentage Calculator:

http://tools.foodsim.com/

EDIT: Since you're using bakers percentages, you must convert the percentages into normal percentages first.  I used 16/27 hydration as per your example.

66.4773 % of starter by weight
33.5227 % of flour by weight

[Link]

Pete-zza and November,

On this site, you two ARE the Hammer of the Gods.

youtube.com/watch?v=4C1iDbEha7U

I really appreciate you help,

Link

[November]

Link,

What I provided was somewhere between wrong and confusing based on your bakers percentage example.  As stated above, you must first convert the bakers percentages to normal percentages.  For hydration you would use 16/27 rather than 16/11.  Also, the target percentage would then be 65/165, not 65/100.

[Pete-zza]

Link,

When I last posted, it had not occurred to me to ask you why you were contemplating the method you described. However, later it occurred to me that you might be able to put the preferment dough calculating tool at http://www.pizzamaking.com/preferment_calculator.html to good use. For example, if you wanted to make a 250-gram dough ball with an overall 65% hydration, using 15% of your starter (as a percent of the total formula flour), with a starter water percent of 53.9% (16/27), and with a typical salt level of 1.75%, the preferment dough calculating tool will tell you how much water and flour to use as part of the final mix to keep the overall formula hydration at 65%. I don’t know if this is the sort of thing you had in mind, but the dough calculating tool would produce the following results using the above example:

Total Formula: Flour (100%): Water (65%): Salt (1.75%): Total (166.75%): Preferment: Flour: Water: Total: Final Dough: Flour: Water: Salt: Preferment: Total:

149.93 g  |  5.29 oz | 0.33 lbs 97.45 g  |  3.44 oz | 0.21 lbs 2.62 g | 0.09 oz | 0.01 lbs | 0.47 tsp | 0.16 tbsp 250 g | 8.82 oz | 0.55 lbs | TF = N/A     9.15 g | 0.32 oz | 0.02 lbs 13.34 g | 0.47 oz | 0.03 lbs 22.49 g | 0.79 oz | 0.05 lbs   140.77 g | 4.97 oz | 0.31 lbs 84.12 g | 2.97 oz | 0.19 lbs 2.62 g | 0.09 oz | 0.01 lbs | 0.47 tsp | 0.16 tbsp 22.49 g | 0.79 oz | 0.05 lbs 250 g | 8.82 oz | 0.55 lbs  | TF = N/A

Peter