So how do I ensure that my pork crackling is crispy?
The key for me is two factors, dryness and hotness.
The pork skin needs to be really really dry. I use kitchen towel to ensure that the pork is as dry as possible. I know some people will rub salt in, but that is basically the same thing, the salt will asorb any moisture on the skin. Personally I find that just using kitchen towel is just as effective.
The next stage is place the pork into a really really hot oven. I have my oven on full and when it has pre-heated, I place the pork in the middle and cook for 15 minutes before turing down the heat to 160℃ or 180℃ depending on the cut of the pork.
As a result, nearly everytime I get a wonderfully crispy crackling.