My next experiment with London Plane was to use various parts of the living tree to stain seasoned timber. I tried different leaves off different trees but the waxy leaves didn't really break down, even after a couple of hours of patiently adding water and mordant and not letting it dry out. The bark created only a brown colourisation. I eventually elected to use the Button balls or seed containers that you find on the London Plane tree - a sort of soft conker.
I chopped the material up very fine and then added it to the boiling water and then reduced it down as much possible. I spent two hours adding water. I used Alum as a mordant as it was readily available and because its powdered I guess, I found it easy to judge the appropriate quantities needed during the process. I added the Alum while the simmering vegetation was still on the stove and so easily settled on the right consistency and colour. When I was happy I removed from the heat and let it cool down. Once room temperature I used a Muller to grind it down to a fine pulp.
When applying to the timber, I selected the palest stock I could fine and finished it to 240 grit and then prepared it with vinegar water solution. Once dry I cut back the raised timber fibres with a very fine abrasive and then applied the stain generously.
The result is not at the brilliant end of the colour scale but is certainly worth the small amount of effort producing a chalky green – not unlike French Grey.