Q.Painting tree trunks
I wonder if you can help? I am an artist living in the Glos/Herford/Monmouthshire borders and for a forthcoming nature/arts festival i want to make a proposal to the organisers of the festival for an arts event, site specific art work. I would like to decorate, using a natural paint (say clay slurry, or other suitable material) a number of tree trunks in a woodland setting. The clay ‘paint’ would eventual and naturally wash off with rain etc., but do you think this would be harmful to the trees at all? What would you recommend?
Thank you for your help
Best wishes
Kate

I'm in the school of thought that this is a unique idea, but there are too many unknowns for me to make an exact recommendation.
Different trees and the type of bark that the tree has, could react differently to this process.
Trees need to breath and even using a natural clay product could compromise the trees.
You could contact the manufacturers of the products you are using to determine the safety of the paint for use on a living tree.
With this being said, painting tree trunks with water based paints is a process that is used at times to help prevent sun scald.
Here is an article about this process.
https://www.gardeningknowhow.com/ornamental/trees/tgen/painting-tree-trunks-white.htm