Welcome to Over50sForum! The site for people over 50 to chat, make friends, discuss, share, and generally be part of something that's fun and friendly :)
I don't get scum but then my tea bag is only in the mug a mini second , I only like weak tea.
Heat the mug/add tea bag/add boiling water /scoop out the tea bag after required time/ then add the milk and not before or you will reduce the temperature of the water leading to scum