Just to be clear, we're talking about packing brown sugar into a measuring cup, not in our luggage! (Although...) Recipes with brown sugar almost always call for it "packed" while most other baking ingredients are sifted or merely scooped. Why the special treatment for brown sugar?
Packing brown sugar just means pressing it firmly into the measuring cup. We find it easiest to fill the measuring cup first, then press the sugar gently down using the back of a spoon. You don't need to use a lot of force. The sugar will compact and leave a quarter-inch or so gap at the top. Use the spoon to fill this in, press the sugar down again, and then repeat as needed until the measuring cup is filled.
What we're doing is pressing out the pockets of air that get trapped between the sticky grains of sugar. If we didn't do this, our volume measurement would be off. We only want to measure the sugar, not the air. Packing the brown sugar is also a way of making sure the measurement is consistent from batch to batch and from cook to cook.
Of course, if we really want to be accurate, we could always weigh the sugar using a kitchen scale instead!
Related: Pantry Problem Solving: Five Ways To Soften Brown Sugar
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Yup, packed light brown sugar is always 218g for me! I love my scale (and Rose Levy Beranbaum's charts in the back of the Cake Bible).
I often come across recipes that do not specify that the brown sugar be packed. Is it implied? I never know what to do!
@jmorme - I never specify in my own recipes that it should be packed, since it is just *what you do* with it, I always assume it's implied, unless you're measuring with a scale.
"Recipes with brown sugar almost always call for it "packed" - so I clicked on the link thinking 'they do? Odd, I've never seen that, I wonder what it is...'
...and was nodding and thinking, hmm, yeah, good point...
....right up until the mention of scales, when I realised why I'd never seen this before - it's because recipes which don't specify dry ingredients by weight (over a couple of tablespoons, that is) are something I've only encountered as an adult on the net, and they generally get put back down pretty sharpish around here... (am I slow today, or what?)
Thank you, caseoftornados. It seems like recipes used to always specify packed (lightly packed or firmly packed), but now they don't.
"I never specify in my own recipes that it should be packed, since it is just *what you do* with it, I always assume it's implied, unless you're measuring with a scale."
And this is the reasoning that makes learning to cook a challenge.
now i need to see that chart in the cake bible! on my way to the library!
Slow Lorus, I go by Rose Levy too, but I often round down to 200 or up to 225, depending on whether the recipe in question could use more moisture or not. Not sure why I do that, but....oh well.
I've always wondered why Americans love to pack stuff into their measuring gear - especially butter seems so troublesome :D
Joyofbaking.com tells me that 1 cup of packed light brown sugar weighs 218 g whereas that of packed dark brown sugar weighs 238 g. No packing necessary.