If you do decide to use half of a syringe remember the size of the jar that you are injecting into. If you inject half of a 10cc syringe into a 1 quart jar...no problem:-)

But if you inject that much into a half pint jar you're going to add alot more water to the substrate. You will have a higher probablility of getting puddles in the bottom of your jar and thats not good.

Just something to consider.