I learnt this nifty little tip when I did Masterchef back in 2009! I lived near a cute little french cafe in Sydney & walked in one day to ask if they could help me prepare for the show. I was so lucky to get hands on experience inside the kitchen & learnt so many amazing tricks for the kitchen & cooking. I always use this one in the summer time.
Note: you can also use a standard drinking glass (the thinner the glass edge is the better the result).
Love Rach xx