Ever since I arrived in London, I’ve been wondering why the black tea I have made here has a horrible oily film on it.
Like the good noodle I am, I googled it, and it turns out that it’s because the water over here is so hard. When you boil water, it excites the calcium and magnesium salts in the water, which the tannins in the tea bind to as it brews. The oxygen in the air makes larger groups form that can no longer stay in solution and then separate from the water.
Why black tea and not green tea or coffee? It’s still there in green tea, but because there is less tannin in the green tea it’s pretty much invisible. Coffee beans have about half the tannin in them as tea leaves, so once again it’s still there but less visible. I think especially instant coffee would mask this effect because it 1. is soluble so may contain agents to assist this, and 2. is weaker in raw content then espresso. Also, I add milk to coffee so that probably masks it as well.
It has no flavour, and is not harmful, but it’s a bit gross and sticks to the inside of the cup. Thus, I have not made it far into the 100 bags I bought. Now, it seems I have to either boil the crap out of the water so that the salts become lime scale in the kettle, or filter the water first.
I’ll buy a filter.