Rinse guava fruits to get rid of impurities and cut-off ends.
3 pounds Guava
Cut guava into manageable chunks and collect in a bowl.
Cut lemon or lime into two.
1 Lemon or Lime
Place guava into a large jam pan with the water and boil guava soft.
1 quart Water, 3 pounds Guava
Blend guava smooth.
Take the guava pulp through a strainer to get rid of the stone-hard seeds. Do that with the full batch.
Take the strained guava pulp back to the heat with the sugar. Squeeze lemon/lime juice in and throw in lemon/lime halves too.
3 pounds Guava, 3 pounds Sugar, 1 Lemon or Lime
Bring to a rolling boil and then keep on a steady heat to reduce jam. When it starts to change color and it has reduced, stir because the jam will start to jump out. Stir frequently at the end when the jam is done.
When the jam appears glossy or translucent, it might be done. Test if done, setting temperature with a thermometer is 220 Fahrenheit/ 105 Celsius. You can test if the jam is set too by dropping some jam on an ice-cold plate. If it's runny it needs to cook a little more. Repeat test until set.
Take out lemon/lime halves and discard.
Pour hot jam into prepared jam jars up to the rim.
Close the jar with a lid and turn it upside down to create a vacuum. Turn it backup when the jar can be touched again to avoid air bubbles.