a big fav of mine, when i did do size work....
load up onto the barbell 120% more than your 1RM, if your back squat was 100kg, then load up 120kg. Set up the safety pins in your power rack so that their about shoulder height or slightly lower. Take the barbell onto your back, then stand up on your toes, hold for 2-3 seconds, then repeat.
From what i've gathered, the smaller the range of motion, the higher amounts of reps needed to elicit hypertrophy. So perhaps you'll need to do 15 or so reps.
As mentioned, alternate between having your toes facing forward & outwards. Do not have them facing inwards.
if that fails...locate some synthol & put it into your calves!!