Setting the “fluid Ounces” of Your Kitchen Scale Is a Lie
I recently replaced my kitchen scale. The new one has all the features I was looking for – negative tare is a big upgrade. But it also has two features that I never asked for and don’t want to. Nobody wants them. I’m talking about the “milliliters” and “fluid ounces” settings, which are complete bullshit.
You see, and I somehow feel uncomfortable explaining this, the scale is the scale. He measures weight. I appreciate that my scale can measure things in grams, which I use the most, or in ounces. These are measures of weight. (Okay, grams measure mass , but in normal kitchen scale use on planet Earth, this difference is negligible.)
On the other hand, milliliters and fluid ounces are measures of volume. The measuring cup holds eight fluid ounces. A disposable water bottle is usually 500 milliliters. These numbers tell you how much space is inside the cup or bottle.
Knowing the volume of something doesn’t tell you how much it weighs. If you empty a water bottle and refill it with Everclear or maple syrup or olive oil or sand or molten lead or helium, it won’t weigh as much as it did when filled. water. The whole reason we have different units for volume and weight is because they are not the same thing!
What does my scale do when it says it measures volume?
So what the hell does the fluid ounces function think it does? Well, it’s just weighing whatever you put on top and then guessing that that object is the density of water. I measured out a fluid ounce of water (using the small measuring cup that came with the cough syrup bottle) and the scale showed it was 1.0 fluid ounce, 1.0 ounce, 29 milliliters, and 29 grams.
All this is confirmed – the density of water is 0.997 g / ml, which means that 0.997 grams of water occupies 1 milliliter of space. Rounding off, one gram is roughly equivalent to one milliliter, and one fluid ounce is roughly equivalent to one (weight) ounce. If you need to add four fluid ounces of water (half a cup) to a recipe, weigh four ounces. But you don’t need the “fluid ounces” setting for this; you can simply weigh four normal (weight) ounces.
If you’re measuring water or something similar, the fluid ounce and milliliter settings are redundant: they simply duplicate what the normal ounce and gram settings report. If you’re measuring something that doesn’t have the same density as water, such as alcohol, oil, or syrup, to name but a few, the ounce and milliliter settings are more than useless. They can cause you to add the wrong amount of an ingredient to your recipe.
How big is this difference in the real world?
For the test, I measured out one “fluid ounce” of whiskey and one “fluid ounce” of Log Cabin Maple Flavored Pancake Syrup.
Alcohol has a much lower density than water, 0.789 g/ml. This means that it is lighter than water, which explains why you need to mix cocktails or the alcohol will float on top. My cheap whiskey was 90 ABV (45% ABV), which means that its actual gravity is heavier than pure alcohol, but still significantly lighter than water.
Meanwhile, syrup has a higher density than water because the sugar dissolved in it adds weight but does not increase volume. If you’ve ever made a simple syrup, you know this: one cup of water plus one cup of sugar makes something like one and a quarter cups of syrup, even if it contains the full mass (and therefore weight) of water and sugar. sugar you combined. Pancake syrup contains even more sugar than regular syrup, so it will be much heavier than water.
The image at the top of the page shows my results. Both cups were scaled to contain one “fluid ounce” of liquid. They are clearly not the same size. I measured them with my little medicine cup: the volume of whiskey (left) is 36 milliliters or 1.22 fl oz. The syrup (right) is 22 milliliters or 0.74 fl oz.
So, if you were making a cocktail for four people and decided to use your scale rather than a measuring spoon to measure out a total of six ounces of liquid (1.5 ounces per person), you would make the drinks a little stronger than expected. 1.83 ounces per person.
On the other hand, if you were to follow a cake recipe that calls for 3.5 fl oz of maple syrup and use your scale instead of a measuring cup, you would end up adding only 2.55 fl oz of maple syrup to the cake. The result will not be as sweet as expected.
(I know the maple pie recipe just says “ounces”, but the UK version says 100 milliliters , which is about 3.4 fl oz. I also used the gravity of real maple syrup, 1.37, in my calculations, although it very similar to fake syrup, 1.31, I measured in my own experiment, in case any of my old chemistry professors check my work.)
Syrup and alcohol are extreme examples, so I chose them. To name a few other common fluids that will offset your measurements:
- Oils are slightly lighter than water (0.917 mg/mL for olive oil).
- Milk is slightly heavier than water (1.04 mg/ml).
- Peanut butter is slightly heavier than water (1.1 mg/mL).
- Honey is much heavier than water (1.4 mg/ml).
So what should be done? Well, if you’re measuring water, any setting will do. If you are measuring another type of liquid, use volume measurements. A measuring cup, measuring spoon, or even a tablespoon will do (one tablespoon equals half a fluid ounce).