Brass Pulley for My TT


I recently had a machine shop make a Brass pulley for me to try, it is working great but; I am seeing some yellowish dust which I assume is brass. Is this normal? I don't have much knowledge of Brass so I am looking for answers??? Will this stop after a while or not? The belt is made of Mylar.. I have cleaned it off a couple times but it is still producing it...
jsman
invictus005,
Yes I agree my other pulley is made from SS, he told me he would make one from SS if I wanted it. 

Update:

So I had the machine shop make another pulley from SS and wouldn't ya know it , it is also leaving a residue. So now it is either the belt itself or something the shop used on the material I guess???


Update:
Turns out it was the belt leaving the residue, kinda weird though none of the belts I used in the past did this... I am thinking maybe because I am near the end of the roll of Mylar had something to do with it?