Actually, Hélène, one of my French readers, has sent me an e-mail with her findings about bamboo charcoal. Since her findings have caused a lot of discussion in French, I think I should translate her experiments in English:
"I use Reverse Osmosis (RO) water for my teas, but I noticed that these wouldn't display there nicest aromas. It was as if they were 'veiled', 'cloudy' behind the taste of water. My water has a measure of 20 mg/l for Total Dissolved Solids (TDS). Now, here is how I use your bamboo charcoals:
I place 1 piece of active charcoal in the cold water in my 1 liter kettle. I bring it to a boil and wait 1 minute before removing the charcoal. The taste of the water becomes more lively. I feel it tickles my tongue a little, but without the mellow feeling I was expecting. When the water was cold, I tested the water again and found out that the TDS remained at 20 on my instrument. I have obtained the same results each time I made the test. Therefore, I conclude that the bamboo charcoal does not add minerals. Then I had an idea: why not add a little salt? Some natural sea salt?
And so I started to make new experiments with different quantities of salt. I came to the conclusion that my teas tasted best when the TDS was around 200-230. Best is to use an instrument, of course, but with some training, I learned to make without it. Actually, for 1 liter of water, 4-5 grains of (big) salt are enough, which is like a pinch of salt.
Important remark: if you add water to the water in the kettle, salt is still there and so you have to be careful not to add to much. For information, my measuring instrument comes from Hanna instruments.
You may wonder about the taste of salt? Actually, I don't feel my water salty at all! It's just if the TDS is above 230 that I start to feel that the water becomes too heavy."
The fact that the bamboo charcoal doesn't add more minerals (maybe there is an exchange of minerals?) is probably due to the fact that filtering bad elements is the main function of active charcoal. In case of RO water, there is not much to filter, so it's also interesting to see that the bamboo still improved that water by making it more lively.
Hélène's idea to use salt is a great intuition, since she didn't know that salt was added to make tea during the Tang dynasty, as was reported by Lu Yu in his Tea Classic. The reason why salt helps to improve water is the same as why they would use it in the old times: salt acts as a taste lifter/enhancer! What a fascinating experience! Thanks again Hélène for sharing!
Of course, you can only add a little salt if your water is very low on minerals. And this is also the reason why the best water does contain some minerals (like Na) to enhance the taste of tea without overshadowing it.
For those who are interested to also 'somehow aquire' bamboo charcoal to improve your water, I use this opportunity to remind you that if you order from my selection, you will receive 2 free pieces of bamboo charcoal with your order!