Combine apples, sugar and ginger liquid in a large, non-reactive pot (use something that can hold at least six quarts, to give your jam space to bubble). Bring to a boil. Skim the foam off the surface of the jam with a large slotted spoon. Let the jam boil, stirring frequently for 25-30 minutes, until the rising bubbles look thick and stick.
If you have a instant read or candy thermometer, use it to check the temperature of the jam. You're hoping for 220 degrees (although I stopped at 218 and my jam has a nice, soft set).
When the jam has achieved the desired temperature and consistency, fill jars, wipe rims, apply lids and tighten rings. Process in a boiling water bath form 10 minutes.
Let the jam sit for 24 hours, then check the seals by removing the rings and lifting the jars by the lid. A good seal means that the lids will hold fast.