What will desolve steamed milk scum the best?!

What will desolve steamed milk scum the best?

I invented a device to clean the milk scum off of the frother arm of a espresso machine, but it doesn't seem to be effective, but it's not because the device doesn't function like it's designed. The operation of this cleaning device involves running watter and this doesn't seem to be as effective as soaking and scrubbing with a toothbrush. So my question is this: What substance, either as a liquid or a non-liquid additive, will be the most effective at disolving steamed milk scum the best?