3 ms·

For more context, sample reference materials from the NIST reference catalogue are not meant to be exceptionally high purity examples of the sample -- SRMs are

by cyphar 2mo ago

For more context, sample reference materials from the NIST reference catalogue are not meant to be exceptionally high purity examples of the sample -- SRMs are usually commercially-produced products. The real value is that each sample comes with a datasheet with incredibly detailed and accurate measurements that are (as you said) used for calibration of measuring devices in industrial settings. To quote a Veritasium video about the topic from a few years ago[1], "the thing you're paying for is not the peanut butter, it's the knowledge of exactly what is in the peanut butter". [1]: https://youtu.be/esQyYGezS7c?t=226 https://youtu.be/esQyYGezS7c?t=226

buildsjets 2mo ago
Truth. I once paid nearly $500 for a set of 17 certified, calibrated wooden pencils, with documentation showing that each one met their rated hardness levels of 9H thru 6B. And for $500, they don't even come with erasers, that is an added-cost option. https://www.gardco.com/product/pencil-hardness-test-kit-astm-d3363-jpia/01t5I0000023pqaQAA https://www.gardco.com/product/pencil-hardness-test-kit-astm...
- foobarian 2mo ago
  Can I ask why :-) Sounds like an interesting project.
  - cwillu 2mo ago
    His link includes procedures, which suggest he was testing the hardness of some surface coating or similar: > For the pencil hardness test, reference ASTM D3363, pencils of increasing hardness values are moved over the surface in a precisely defined way until one lead damages the surface. Surface Hardness is defined by the hardest pencil grade which just fails to damage the surface. > Observe the pencil track. Sufficient pressure must have been applied either to cut or damage the coating or to crush the lead pencil point. > If neither coating damage or pencil point crushing is observed, repeat the test until a definite observation is made. > If scratching or damage of the surface occurs, proceed with the next softer pencil grade and repeat the testing process until a pencil lead grade is found which crushes and does not damage the coating. > If crushing of the hardest lead should occur, the coating is therefore extremely hard and is beyond the measuring range of this test
  - wildzzz 2mo ago
    You use the kit to test the harness of a finish coating, like a paint or a ceramic coating for cars. Pencils have their own hardness scale which can be used to gauge the hardness of the coating. Its really more of a relative qualitative test than quantitative as you'd use this for sample/coupon testing identical coatings. There are more absolute, quantitative methods to measure various hardness characteristics (scratch, indentation, and rebound). Like you'd use the pencil kit on a factory floor to make sure each paint sample performs the same, the sample being a small area on the product or a plate that's painted the same way.
    - 8note 2mo ago
      the pencil aspect is because its easy for a person to carry and take notes with? and you dont need to fit the car into a proper harness tester?
      - wildzzz 2mo ago
        No, these are expensive pencils that have high quality assurance to make sure the graphite is as hard as it's supposed to be. You use a jig to hold the pencil in a specific way each time. Don't think of it as a pencil, it's a kit of rods made from graduated compositions of graphite and clay. You could write with one but that's like making a PB&J with the NIST peanut butter, a waste of money.
  - buildsjets 2mo ago
    The pencil hardness scale is commonly used to assess paint film hardness by checking what is the softest pencil that can mar the surface when you scratch it with a given force. In this case, we needed to assess whether exposure to a certain chemical degraded the integrity of the paint coating that we were counting on for corrosion protection.
- MikeTheGreat 2mo ago
  I'd like to ask a more specific question than my sibling's excellent "Wait, why?" question :) Why offer erasers on these things? The procedure described below has nothing to do with using these as pencils, and at $500 for a pack I can't imagine anyone, anywhere casually drawing with these. (Is there another procedure, similar to the one described below, except instead of dragging the pencil tip across a surface you drag the eraser across it? )
  - buildsjets 2mo ago
    I’d suggest you read “The TSO’d Pencil” to understand the reference. Http://www.rstengineering.com/rst/articles/tsodpencil.pdf
    - MikeTheGreat 2mo ago
      :) I had no idea this reference existed, or that it's a a fun, though dystopian, read. Thanks! :)

by cyphar 2mo ago

buildsjets 2mo ago

Truth. I once paid nearly $500 for a set of 17 certified, calibrated wooden pencils, with documentation showing that each one met their rated hardness levels of 9H thru 6B. And for $500, they don't even come with erasers, that is an added-cost option. https://www.gardco.com/product/pencil-hardness-test-kit-astm-d3363-jpia/01t5I0000023pqaQAA https://www.gardco.com/product/pencil-hardness-test-kit-astm...

foobarian 2mo ago
Can I ask why :-) Sounds like an interesting project.
- cwillu 2mo ago
  His link includes procedures, which suggest he was testing the hardness of some surface coating or similar: > For the pencil hardness test, reference ASTM D3363, pencils of increasing hardness values are moved over the surface in a precisely defined way until one lead damages the surface. Surface Hardness is defined by the hardest pencil grade which just fails to damage the surface. > Observe the pencil track. Sufficient pressure must have been applied either to cut or damage the coating or to crush the lead pencil point. > If neither coating damage or pencil point crushing is observed, repeat the test until a definite observation is made. > If scratching or damage of the surface occurs, proceed with the next softer pencil grade and repeat the testing process until a pencil lead grade is found which crushes and does not damage the coating. > If crushing of the hardest lead should occur, the coating is therefore extremely hard and is beyond the measuring range of this test
- wildzzz 2mo ago
  You use the kit to test the harness of a finish coating, like a paint or a ceramic coating for cars. Pencils have their own hardness scale which can be used to gauge the hardness of the coating. Its really more of a relative qualitative test than quantitative as you'd use this for sample/coupon testing identical coatings. There are more absolute, quantitative methods to measure various hardness characteristics (scratch, indentation, and rebound). Like you'd use the pencil kit on a factory floor to make sure each paint sample performs the same, the sample being a small area on the product or a plate that's painted the same way.
  - 8note 2mo ago
    the pencil aspect is because its easy for a person to carry and take notes with? and you dont need to fit the car into a proper harness tester?
    - wildzzz 2mo ago
      No, these are expensive pencils that have high quality assurance to make sure the graphite is as hard as it's supposed to be. You use a jig to hold the pencil in a specific way each time. Don't think of it as a pencil, it's a kit of rods made from graduated compositions of graphite and clay. You could write with one but that's like making a PB&J with the NIST peanut butter, a waste of money.
- buildsjets 2mo ago
  The pencil hardness scale is commonly used to assess paint film hardness by checking what is the softest pencil that can mar the surface when you scratch it with a given force. In this case, we needed to assess whether exposure to a certain chemical degraded the integrity of the paint coating that we were counting on for corrosion protection.
MikeTheGreat 2mo ago
I'd like to ask a more specific question than my sibling's excellent "Wait, why?" question :) Why offer erasers on these things? The procedure described below has nothing to do with using these as pencils, and at $500 for a pack I can't imagine anyone, anywhere casually drawing with these. (Is there another procedure, similar to the one described below, except instead of dragging the pencil tip across a surface you drag the eraser across it? )
- buildsjets 2mo ago
  I’d suggest you read “The TSO’d Pencil” to understand the reference. Http://www.rstengineering.com/rst/articles/tsodpencil.pdf
  - MikeTheGreat 2mo ago
    :) I had no idea this reference existed, or that it's a a fun, though dystopian, read. Thanks! :)