Make sure you use the correct proportion of nicotine base when mixing, so that you end up with a liquid that's in the nicotine strength range you're aiming for.
e.g.: If you bought 72mg nic base and you're aiming for 16mg strength in your finished liquid, 72 divided by 16 = 4.5 , expressed as a percentage that equates to 22.22 so for every 10ml batch you mix up, you should be aiming to use around 2.2ml of nicotine base in your 10ml mix to end up with 16 mg.
If you bought a different strength nicotine base, then just change the first number of the calculation ( e.g. for 48mg nic base, 48 divided by 16 = 3, which equates to 33%, so 3.3ml of nic base in a 10ml mix would give a finished mix of 16mg strength).
