Sold by weight, not volume

I recently rediscovered a favorite Australian candy bar of mine, Violet Crumble. It’s made of “honeycomb” on the inside and coated with a thin layer of chocolate. The chocolate provides not only flavor but also function: honeycomb is hygroscopic (absorbs water from the air), and the chocolate forms a barrier to keep water out (and the honeycomb dry and crunchy).

Browsing the food label highlighted some interesting differences between Australia’s take on nutrition and our own. Most of the information is the same, although metric units are used (naturally) and energy is listed in kilojoules rather than calories. The ingredient list caught my eye because it associates a percentage with each item, something I’ve never seen in the U.S. And in this case, Violet Crumble was listed as being 59% chocolate and 40% honeycomb. As you can see from the picture, this clearly is not determined by their volume, but rather something else. I determined via google that these percentages are based on “ingoing weight” (prior to cooking/baking/mixing/preparing).

My candy bar is 17 cm long by 3.5 cm wide by 2.2 cm high (on average), for a total volume of 130.9 cm3. The chocolate layer appears to be about 1 mm thick, yielding a shell volume of ~21 cm3, leaving ~110 cm3 for the honeycomb. The whole bar weighs 50 g, so if we apportion weight using the above percentages, that’s 29.5 g of chocolate and 20 g of honeycomb. We can then determine the density of each, yielding 1.4 g/cm3 for chocolate and 0.18 g/cm3 for honeycomb. The only relevant density report I could find online is a figure of 1.325 g/cm3 for semi-sweet chocolate, so this at least seems reasonable. And just think, all this was possible because Australians include percentages in their ingredient lists!