|Dust from 200m of filament|
I don't consider that I do a huge amount of printing but clearly there is quite an amount of dust and fibres that might block the extruder and contaminate the extruder mechanism.
Obviously if it doesn't get stuck somewhere, it ends up in the plastic.
|Tesco pan cleaning sponge|
The sponge is simply wrapped around the filament and held in place with a cable wrap that came keeping one of the cables neat and tidy during shipping.
There are designs out there on Thingiverse such as this for example.