Axel, a regular blog reader posted this astonishing account of how he used cooked pu-erh to paint wood on Yahoo! Tea-Disc Group. He also sent me the pictures of his work. You'll be able to see that he obtained a color very close to the one used for bamboo tea trays:
"Using puerh for anything else than tea drinking may seem like an odd and perhaps sacrilegious idea. I've found that it can also be used to stain wood, with very nice results. Like many other great ideas throughout history (penicillin being discovered after a forgetful lab assistant left his cheese sandwich out for too long, for instance), the idea came to me by accidental means. Having over-steeped a brew of cooked puerh and noticing how dark and opaque the liquid was, it reminded me of a product I sometimes use to dye wood. If puerh can stain a table cloth, it can certainly stain wood...here's how to do it.
For starters, you'll need some cheap, cooked puerh. The process also works with that 1972 vintage you've been saving for a special occasion, but for those on a budget while experimenting on such things, the cheaper the better. The tea doesn't have to taste great. It just has to brew up an extremely dark and concentred infusion.
I originally used a piece of cooked beeng cha that I had blindly purchased a year ago. From a taste point of view, the tea was a disaster...notes of wet dirt combined with a hint of roofing tar best describe its taste. Its aroma is similar to that of a can of coca-cola that has been left open in the sun over the weekend. I didn't pay much for this tea, so I basically got what I paid for. It was a learning experience which resulted in the loss of a customer for a local tea vendor who shall remain anonymous. Such is the price to pay for the sake of art.
To make the dye, put some cooked puerh into a container (a non-porous teapot is ideal, as this won't ruin your teapot - I use a metal teapot of the kind used in dim sum places) and pour boiling water over it until the water covers the tea. Let this sit for a few hours and then pour out the liquid through a strainer into a bottle or jar. The resulting brew is extremely concentrated and I would strongly advise against tasting it unless you wish to liquefy your internal organs. I imagine one can get similar results by boiling the puerh for about ten to twenty minutes. If the brew is not concentrated enough, you can reduce it in a pan, much like a sauce, until it thickens a bit. This will speed up the process of staining wood, although I like to use it as is.
Once your puerh wood stain is ready, you can keep it in a closed jar or bottle. I keep mine well-sealed and in the fridge, to keep it from fermenting into something really unpleasant. Just don't mistake it for Guinness on St-Patrick's day, unless, as mentioned earlier, you wish to pay a visit to your local ER.
The staining process itself is fairly straightforward. The first step is to prep the wood as usual before staining it with any water-based wood dye. Be aware that any water-based dye raises the grain of the wood. To prevent this, wet the wood after having sanded it and let it dry, then sand it again before applying the dye. You can then apply the puerh dye with a brush or cloth. Before applying another coat, let it dry out completely then polish the surface with a soft cotton cloth. The more coats you apply, the darker the wood will get. Wood dyed with puerh is brown with a light red tone, much like the tea. It pays off to be patient, because the colour only starts to really show after three or four coats. The nice thing about this process is that it gives a softer, more natural look to wood than most commercial products. It also "antiques" the wood and is very forgiving and easy to work with once you get the hang of it. It's also eco-friendly and relatively inexpensive.
The only drawback I've found is that it is not possible to varnish the stained wood with water-based acrylic varnishes. These actually discolor the stain. I finish my pieces with furniture-quality beeswax, to great results. If anyone of you tries this with solvent-based finishes (polyurethane varnish) or oils, it would be most interesting to share the results. If you ruin your mother-in-law's mahogany buffet, you're on your own and I am not legally responsible for any harm caused. If you create a masterpiece and sell it as an antique to a misguided fool, I'll accept 35% of the earnings as a gracious gift."
Here a comparison between a block of lime tree and the bamboo box in which the small xishi teapot came. The bamboo box became a reference for the color to obtain.
A bar of white pine tree before and after the treatment. Here, the wood received 8 layers of puerh paint!