The purpose of this comparison was to observe any difference between using sodium bicarbonate and potassium bicarbonate for alkalinity.
For this comparison, I made two different batches of water. The first one was my standard recipe, and the second was an altered one with potassium bicarbonate swapped in for sodium bicarbonate.
For this test I used Imperial Lu Shan Yun Wu Green Tea of Jiangxi from Yunnan Sourcing, since I have drank a good amount of it, and know it pretty well. The test was not done blind, but with the help of my brother, who I know to be incredibly uninvested in my experiments, and very unbiased.
We used the exact same brewing parameters for each tea: 4.00 grams of tea per 95mL gaiwan, brewed at 176F. Brewing times were also kept consistent with a timer.
Result: We found that the water which contained potassium bicarbonate tasted more mineral and bitter, and this was mostly apparent in the aftertaste. We also found that the wet leaves which were brewed using the potassium bicarbonate recipe had a much fresher aroma. The wet leaves brewed with the standard sodium bicarbonate recipe had a more broth-like, savory aroma. This particular difference was not subtle. There was no difference in the appearance of the brew or the leaves.
Conclusion: Based on the result of this quick test, I don’t see a reason to taste more teas with the potassium recipe. Though the difference was slight, I definitely prefer the original recipe.