Flour, by any measure

I made a batch of cookies last week, from a recipe I have used several times before with great success. But these cookies were the fail. They were thin, almost runny when they came out of the oven, and cooled to be hardened little slivers of sugar. Grump.

I played with several different theories about what might have gone wrong. The Baker Down The Street patiently explained to me that baking powder and baking soda lose their efficacy over time, and she recommended buying new boxes of both each year, just before the Christmas baking extravaganza begins. Okay, good advice, but it didn’t feel like the sole culprit for the cookie debacle.

As I thought about it more, it felt like the amount of flour might have been too light. About a year ago, I developed a preference for measuring out my flour by weight. I have a great little kitchen scale, and I use the conversion factor printed on the bag of flour (usually 30g to ¼ cup), but I was beginning to believe that was leading me astray.

So, I’ve started a spreadsheet. Over the next few weeks, I’m going to measure out flour twice, noting how much a cup of flour should weigh according to the bag, and how much it actually weighs for me. I’m also tracking the daily humidity, as I’m guessing that’s affecting the weight.

Here’s the spreadsheet.

Only two data points so far, but there seems to be something to my suspicion. I’m looking forward to getting over a dozen entries and then trying to best-fit it to a formula. Linear, exponential, power function… any guesses? Yeah, yeah, I’m a geek. Don’t look so surprised.