I am trying to make caramel ice cream from the Silver Spoon. I'm not entirely sure what they mean by the word "skim" at the start of the recipe:

Put the sugar (100g) in a pan with 1 tbsp cold water and set over a low heat until it has melted. Increase the heart to medium, skim and, when it goes golden red in colour, pour in 5 tbsp hot water and remove from the heat.

There was a bit of a crust of bubbly sugar on the top surface of the pan, but how are you supposed to skim that? Perhaps it's something lost in translation from the original Italian recipe?