Preparation of Verdigris for Emerald

Source

Papyrus Graecus Holmiensis / Stockholm Papyrus, Method 74, translated by Earle Radcliffe Caley.

Question

Does vinegar type or oiling the copper meaningfully change the verdigris produced?

Materials

• Copper sheet
• 5% white vinegar
• 50% vinegar
• Balsamic vinegar
• Olive oil
• Mason jars
• Nylon fishing line
• Pumice stone

Method

• Cut copper into strips and cleaned the surfaces with pumice and water.
• Prepared oiled and non-oiled copper samples.
• Suspended the copper over vinegar inside sealed jars without touching the liquid.
• Scraped verdigris morning and evening for two weeks.
• Weighed sample yields and compared color, texture, and copper surface changes.

Observations

• 5% vinegar produced the highest average yield in the small sample set.
• 50% vinegar samples left brighter copper after scraping, suggesting less unwanted copper oxide.
• Balsamic vinegar produced darker material.
• Oiled samples scraped off waxier and more cohesive than non-oiled samples.

Result

• The numbers were suggestive rather than definitive.
• The physical differences were more interesting than the weight data alone.

Uncertainty

• The small sample size limits statistical confidence.
• Weight alone may obscure historically meaningful differences in purity, texture, and handling.
• The source specifies sharp vinegar but does not define vinegar type or oil with modern precision.

References

• Caley, Earle Radcliffe. The Leyden and Stockholm Papyri.
• Papyrus Graecus Holmiensis / Stockholm Papyrus.
• Kuhn, Hermann. Verdigris and Copper Resinate.
• Cobb, Cathy, and Monty L. Fetterolf. The Chemistry of Alchemy.

Next

• Repeat with more samples and add chemical or microscopy work if practical.

Related Projects