This isn't a usual "I did something wrong and we had a disaster" post, because I haven't had many disasters recently, and the ones I *have* had (I cooked last night ... I ate two lumps of omelette) are for known reasons (I neglected to re-oil the non-stick frying pan after cooking one omelette successfully). Instead, this is the first of a possibly recurring series, pondering about weights and measures.
I will make presumptions here when I don't understand something. I think this will be the best way to identify my lack of understanding. I will only then research the subjects that I find problems with, to prove (test) my assumptions.
The Fluid Ounce
An ounce ... but fluid? As opposed to a solid ounce? I note that it's not "liquid ounce", so I suggest that "fluid" might refer to granules or powder, as much as a solution or emulsion. The markings for fluid ounces are on our measuring jug, between the ml and the pint markers. This suggests that it's a volume measurement rather than a weight measurement, but I have no idea why a modification (in this case "fluid") of a weight measurement converts to a volume measurement. I don't think we get a "fluid gram", so I presume it's not a standardised thing to do.
I just showed this screen to my partner, and she immediately said "the fluid gram is the millilitre."
Me: "What about the cubic centimetre?"
Her: "The cubic centimetre and millilitre are the same measurement for water, but not necessarily for other liquids".
Our conversation continues into fluids, and she said that she measures powers in weights rather than in volumes (I might be correct in my fluid-dynamics assumption ... I'll need to research it).
This brings me on to my next problem, of measuring in weights rather than in volumes:
I have lots of cups, of different sizes. If I want to make sure I have a consistent amount of "stuff" in a recipe, I could see myself copying the builders' concrete formula. That is: one spade of cement, two spades of sand, three spades of aggregate, will give you a consistent mortar, regardless of the size of the spade or the expertise of the builder. Moving this to cooking, I can see that one cup of flour, one cup of sugar, one cup of cocoa, will always give you a consistent mixture if you use the same cup (although I don't know what you could make from those items in a mix).
However, can different substances not be tamped to different degrees? I can see that sugar would be impossible to squash, but that cocoa would be easy; so I would be able to alter the ratio of items in the mixture if I was using volumes.
Therefore, as my partner just said, we use weight as a measure of the amounts of dry items ... although Americans use the Cup. Bugger, I don't suppose that a Cup is actually a weight measurement rather than a volume measurement, is it?
I've just been served dinner (steamed haddock, chips & asparagus), so I'll need to add a post about tea- and table-spoons later.