When tested with an XRF instrument this blue glazed ceramic bowl by Heath Potteries of Sausalito, California (year of manufacture is unknown) had the following readings:
Food Surface / Blue Glazed Interior of Bowl
- Lead (Pb): 838 +/- 28 ppm
- Barium (Ba): 585 +/- 38 ppm
- Antimony (Sb): 25 +/- 12 ppm
- Tin (Sn): 284 +/- 14 ppm
- Zinc (Zn): 876 +/- 44 ppm
- Copper (Cu): 8,210 +/- 187 ppm
- Iron (Fe): 3,780 +/- 187 ppm
- Bismuth (Bi): 36 +/- 10 ppm
- Vanadium (V): 106 +/- 23 ppm
- Titanium (Ti): 918 +/- 56 ppm
- Indium (In): 28 +/- 8 ppm
- Cobalt (Co): 5,923 +/- 200 ppm
Brown Glazed Under Side of Bowl
- Lead (Pb): 125,000 +/- 4,500 ppm
- Barium (Ba): 6,152 +/- 433 ppm
- Tin (Sn): 10,200 +/- 600 ppm
- Zinc (Zn): 16,900 +/- 700 ppm
- Copper (Cu): 306 +/- 68 ppm
- Iron (Fe): 8,277 +/- 498 ppm
- Vanadium (V): 2,504 +/- 179 ppm
- Titanium (Ti): 14,500 +/- 800 ppm
- Zirconium (Zr): 13,600 +/- 700 ppm
- Manganese (Mn): 1,479 +/- 328 ppm
At first glance it appears that the base (underside) of this bowl is unglazed, however upon closer examination the underside is glazed with a brown glaze that is slightly lighter in shade than (but very similar to) the brown color of the substrate of the clay.
Each area was tested for a minimum of 120 seconds (two full minutes) using an XRF instrument testing in “Consumer Goods” mode. All test results reported on this blog are science-based and replicable. Metals not listed in the reading sets above were not detected by the XRF in “Consumer Goods” mode. All tests are also done on a freshly calibrated instrument.
For context (so you have a better understanding of what the above numbers may indicate): newly manufactured items intended for use by children are considered unsafe (and illegal) if the glaze, paint or coating is greater than 90 ppm Lead (as detectable with an XRF.) Dishware (modern and vintage) is not regulated in the same way (or with the same strict standards) as toys and other items intended for use by children.
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