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I bought a scale to measure very small quantities in 0.01 increments.
The scale has a calibration weight of 50 grams and it measures so +/- an error as expected.
My intention for the scale is to measure powder/herbs.
To try it I have a measuring spoon that says 1.25 ml and I used cinnamon as a sample and scooped it, use a knife to flat out the top and when I weighed it the scale reported 0.5 grams while I was expecting 1.25 grams.
I tried with regular sugar (not powedered) and the weight reported is the same as the measuring spoon e.g. for 2.5 ml the scale reports 2.5 grams etc.
So now I am confused. Is there a difference when using powder and measuring spoons? What's the issue here?

Jim
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    See [this table](https://www.aqua-calc.com/page/density-table/substance/spices-coma-and-blank-cinnamon-coma-and-blank-ground). Ground cinnamon has a density of 0.5 grams per cubic centimetre (per millilitre). 1 cubic centimetre = 1 millilitre. So, your scales and measuring spoon are correct. – Billy Kerr Jan 31 '23 at 12:48
  • @BillyKerr: Thanks! So what is the difference with oil or sugar? I can't find those in the page you shared. – Jim Jan 31 '23 at 12:54
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    All ingredients have different densities. It just so happens that some will be equivalent in millimetres as they are in grams. You can't assume all ingredients will weigh the same based on volume. – Billy Kerr Jan 31 '23 at 12:59
  • @BillyKerr: Very helpful especially the page you shared thank you – Jim Jan 31 '23 at 13:01
  • @BillyKerr: Here https://www.aqua-calc.com/page/density-table/substance/sugar I see that sugar is 0.49 g/cm³ which is less than cinnamon though. How is it that for sugar the measurement matches? I thought it should have been 1 g/cm³ – Jim Jan 31 '23 at 13:03
  • It might depend on how fine or coarse the sugar is ground, or even whether you compacted it in the measuring spoon. Granulated sugar has more air gaps between the grains making it less dense than say powdered sugar, which will pack more densely. This is why measuring by volume is not accurate. Better to use your scales if the measurements are crucial to a recipe. – Billy Kerr Jan 31 '23 at 13:07
  • That site says granulated sugar is 0.79g/ml while cinnamon is 0.53g/ml. So cinnamon is less dense than sugar and would weigh less than the same volume of sugar. – Peter Moore Jan 31 '23 at 13:32
  • What happens if you use water, for which it should match? And measure at several multiples of 2.5ml, plotting a graph of mass vs volume? – Chris H Jan 31 '23 at 13:38
  • @ChrisH: With water is very tricky to fill it to the brim. For 2.5 ml the scale shows 2.4021 gr and for 5ml there is a slightly bigger deviation but I also think that the water goes beyond the brim of the spoon too – Jim Jan 31 '23 at 14:06
  • @Jim yes, you'll get a meniscus. Your spoon probably isn't perfect either. But the value you're getting for water is an acceptable sort of error – Chris H Jan 31 '23 at 14:11
  • @PeterMoore: I guess I am not using the page properly. I added `sugar` in the url i.e. https://www.aqua-calc.com/page/density-table/substance/sugar and checked the table column which says 0.49. How can I see the report for granulated sugar? – Jim Jan 31 '23 at 14:14
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    The site's confusing. That link takes me to "SUGAR 'N SPICE [brand], PAPRIKA". I think if you uncheck "Branded Foods" when you search you get better results. – Peter Moore Jan 31 '23 at 14:42

2 Answers2

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I think you are mixing up volume and weight.

Your spoon is measuring a volume, giving you ml of the substance that you scooped. To convert this volume into a mass, you need to multiply it by the substance density in mg/ml.

Additionally, powders and coarse materials like ground herbs will not have a constant density, because of the empty spaces between their parts, which change with how you pour/scoop them.

Try shaking a container filled to the edge with herbs, and see how the level seems to diminish as the herb fragments pack better.

If you want to carefully measure weight for loose substances like powders or ground material, use a scale, not a spoon.

As a reference for how big this effect can be, I routinely store my muesli in a glass jar. By directly putting the muesli in the jar, about 10% remains in the bag. After gently shacking the jar, the whole content can fit in.

L.Dutch
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  • So what is the difference when measuring with sugar or oil and the measurement matches? – Jim Jan 31 '23 at 12:52
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    @Jim: liquids are going to give you consistent volume measurements, but it may not be 1g/mL (although many are close). Granulated items have the potential to pack differently based on a lot of factors so trap air and won’t be a consistent grams per mL but if item is dense the amount of air might bring it back near 1g/mL – Joe Jan 31 '23 at 14:51
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Volume and weight are two different measurements, a spoon of powder won't weigh as much as a spoon of oil as they have different densities.

However, a handy thing to keep in mind is that with the metric system 1 gram of water = 1ml in standard conditions. So, a flat spoon of water at 1.25ml will weigh 1.25 grams. As long as your scale measures that accurately then it is correct.

Spagirl
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GdD
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  • I did the test of the water. It was roughly the same. It was very difficult to add water exactly at the brim of the spoon – Jim Jan 31 '23 at 18:43
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    At this level of precision the scale should be far better than the spoon. That's why I commented under the Q that it might be a good idea to plot a graph of g on the y axis against ml or spoonfuls on x – Chris H Feb 01 '23 at 11:11