DLUnicorn wrote a recipe for making your own saline to flush wounds with. It said "Boil 1/4 tsp salt in water for 5 minutes, then cool". But how much water? And can you store this in your fridge, or does it need to be "fresh". In an emergency pinch, could you use a squirty bottle of contact lens saline, then use your own home-made? Thanks in advance.