These elements have no mercy and stick to anythingthey come into contact with, the result is that your coffee will soon develop abitter and undesirable tonal quality, not only affecting the taste of theespresso but also affecting the aroma, in extreme cases tannin deposits havebeen known to cause partial blockages to the path of the water before it hitsthe portafilter or filter holder. Tannin deposits are well known to be one ofmain causes for a complaint of bitter-tasting espresso.

However, all is not lost as you can beat thisproblem with regular backflushing of the group head using PulyCaff Powder and ablind filter basket, so long as your machine has a 3-way solenoid (which allknown commercial coffee machines do). Puly Back Flush Powder is the food-safe,high concentrate, fast-dissolving product to use for best results.