Self-Preservation 4 (Crinkle or not?)

When you’ve reached a ‘rolling boil’ (...you might think you’ve reached a rolling boil, but unless it’s a truly homogeneous ‘mesh’ of tiny bubbles, you might not have!), it’s time for the ’crinkle test’.

Using a spoon, put a very small sample of the marmalade liquid onto a cool dry plate. Blow continuously across the surface of this sample for about a minute to cool it rapidly. Then push your fingernail gently through the liquid. When you’ve reached the ‘setting point” the surface will ‘crinkle’ ahead of your fingernail. Eureka! (But keep boiling and testing if there’s no clear ‘crinkle’!)