Nora, Rangiora.

Magic Oven Cleaner – In a roasting dish put 3 tbsp ammonia, 3 tbsp washing powder and then fill with 2 litres of boiling water. Place in the oven, block all vents and leave overnight. Switch oven off at the wall. Next day use the water to wipe out the oven and clean the racks. So easy and baked on gunk comes off with very little effort. -