Black streaks

[Novastucco]

Hi. I am doing a white Venetian plaster but when I burn it I get many black marks, I am using the marmorinotools tool that according to avoid this but they keep coming out. What can I do or what am I doing wrong?

Thank you !!

 

[LuisC&S]

Hey, have you sorted this out? I will burnish with a hard plastic trowel or use Come Bianko. Much better than the marmorino tools trowel.