Why is my crackling not crispy?

Dry skin, salt and a blast of high heat — the three requirements, and moisture is what defeats all of them.

Difficulty: intermediate
Time: 30 min
Read: 3 min
Safety: caution

Short answer

The skin must be bone dry. Score it, salt it, and leave it uncovered in the fridge overnight, then start in a very hot oven. Wet skin steams and will never crisp however long you cook it.

Crackling is skin that has dried out and then puffed in high heat. Every step is about removing water first and applying enough heat second — and any moisture, including from a covered tin, prevents it entirely.

Safety

Hot fat spits when the oven door opens on high heat. Stand back, use long oven gloves, and be careful transferring the tin. Pork must still be cooked through — crackling is about the skin, not a reason to undercook the meat.

What you'll need

Pork with skin on
Sharp knife or blade
Salt
Kitchen paper
Wire rack (optional)

Step by step

Score the skin without cutting the meat.Lines about a centimetre apart through the skin and into the fat but not the meat. Cutting into the meat lets juices out onto the skin, which is exactly what stops it crisping.
Dry it thoroughly.Kitchen paper, firmly, into the scores. Then leave it uncovered in the fridge overnight if you can — the cold air dries the surface far better than anything else.
Salt it generously just before cooking.Rub salt into the scores. It draws out the last of the moisture. Salting a day ahead also works, but wipe off the liquid it draws out before roasting.
Start very hot.220-240°C for the first 20-30 minutes. This is the blast that puffs the skin. Then drop the temperature to cook the meat through.
Never cover it.Foil traps steam, and steam is the enemy of crackling. If the meat needs protecting, cover the meat and leave the skin exposed.
Keep the skin out of the juices.A wire rack, or a bed of vegetables. Skin sitting in liquid in the bottom of the tin will not crisp.
Finish under high heat if it is still soft.Take the joint out, cut the crackling off, and put it back in a very hot oven or under the grill on its own for a few minutes. This rescues nearly every failure.
Rest the meat separately from the crackling.Covered meat steams the crackling. Take the crackling off first and let it sit somewhere dry.

Tips

Ask the butcher to score it. They do it properly and quickly, and getting the depth right is most of the job.
Free-range pork with a thicker skin crackles better. Very thin supermarket skin sometimes will not crisp whatever you do.
Pouring boiling water over the skin then drying it thoroughly is a traditional trick that opens the scores and helps a great deal.

If it doesn't work

Soft and chewy

Cause: Moisture on the skin — Fix: Cut it off and blast it separately in a very hot oven or under the grill.

Crisp in places, soft in others

Cause: Uneven thickness or the joint sitting in juices — Fix: Use a rack, and rotate the tin partway through.

Burnt before the meat is done

Cause: Too long at high heat — Fix: High heat for the first 30 minutes only, then drop to 170-180°C.

Skin did not puff at all

Cause: Not dry enough, or scoring too shallow — Fix: Overnight uncovered in the fridge, and score deeper through the fat.

Questions people ask

How do I get crispy crackling?

Dry skin, deep scoring, plenty of salt, and a very hot oven for the first half hour. Never cover it, and keep it out of the juices.

Can I rescue soft crackling?

Yes. Cut it off the joint and put it back into a very hot oven or under the grill on its own for a few minutes.