Plant-Based Solutions for Metalcraft: Alternative Non-Toxic Copper Patination Method from Thai Fruits and Vegetables

Abstract

The patination process in metalcraft traditionally involves highly corrosive and toxic chemicals. Although low- and non-toxic patination methods have been explored, plant-based materials remain under researched. This study, conducted in Bangkok, Thailand from March to June, set objectives to experiment with Thai fruits and vegetables’ ability in creating patinas on copper, catalog those producing distinctive results, and provide a discussion and suggestions for this alternative, plant-based, non-toxic patination method in metalcraft. Eight solutions were applied to 0.1mm thick copper sheet for 3-4 days, resulting in a variety of non-toxic patinas. It was found that plant solutions with pH 2 created a matte green patina, while pH 4-5 produced iridescence. However, despite being both pH 4, Tomato created matte green, and Mango produced iridescence, suggesting sweeter juice content leads to iridescence. SEM analysis revealed that thicker layers of corrosion products appear green, while thinner layers appear iridescence, with no significantly difference in components. The eight Thai fruits and vegetables solutions resulted in patinas in a range of textures and hues from matte green to shiny iridescence and semi-matte gray-purple. These plant-based solutions offer an eco-friendly option for jewelry, product design, and metal craft.