Lab Results

[Justin0455]

Hi the lab did a leachate test because it seems there could be a copper glaze on this stoneware although maker says there is not. I wanted to make sure it’s food safe. The lab says it leached copper but I don’t know how high the leachate concentration is based on the results. It doesn’t say what is considered a normal result. Does anyone here know how to interpret this? Here’s the lab results.

[High Bridge Pottery]

The bold heading is your results of 0.207 micrograms per milliliter and if you multiply the total volume of leachate (acetic acid) 192 x 0.207 you get 39.744 or 40 micrograms total. The reporting limit of 0.005 is the lowest values they can accurately report.

 

In this they say there's no legal limit for copper but 1.3 milligrams per liter is safe for drinking water and you have 207 micrograms per liter or 0.207 milligrams so about 15% of what can be inferred as "safe"

https://ceramicartsnetwork.org/ceramic-recipes/recipe/Copper-Oxide#

[Callie Beller Diesel]

In the absence of a better guideline, most people compare leachate values to drinking water standards. The accuracy of doing this is up for debate because pottery isn’t your plumbing pipes, but it’s at least a starting point. Your leachate value is going to decrease with an item’s use, not fluctuate like drinking water running through miles of pipes. It’s further complicated by the fact that you drink acidic beverages out of some containers which might ….you get the idea. 

The Government of Canada has an Aesthetic Objective recommendation of 1 ppm of copper for staining and smell/taste, and a maximum value of 2 ppm for health purposes. Your leachate value is well under both those numbers. 

The US EPA has an “action level” of 1.3 mg/L, or 1.3 ppm for copper. You’re well under that too.