The infamous TPD. A set of regulatory measures to protect European citizens. A very good thing that allows vaping enthusiasts to enjoy high-quality e-liquid. Unfortunately, the Tobacco Product Directive has also brought its fair share of inconveniences, for example the 2 ml limit in pod tank size. Or another issue, which is relevant to this article, the 10 ml limit to nicotine-containing e-juice bottle size.
Whether you are just trying to save money, or just to work around this annoying limitation, you probably use nicotine boosters.
Vape companies have planned ahead, and you can easily find what are known as Mix-n-Vape product ranges. This means a 0 mg e-juice bottle in which flavours have been strengthened ahead of time, as they will be diluted. These bottles are also filled to about 80%, leaving room for your boosters (a 50 ml bottle will have 10-15 ml empty so you can just squeeze the booster in).
How it works
This TPD limitation has an advantage: it allows you to choose your nicotine strength with high precision (which is important): do you prefer 7? Or 2.5 mg? Well you can, it’s just a matter of proportion and a little mental math, and I’m going to tell you how.
So in this case we are diluting a 10 ml booster, measured at 20mg nicotine, into a 50 ml base. What is the nicotine strength of the mixture? Let’s calculate. We diluted 20 mg of nicotine in 60ml total. This means 6 times less nicotine than in the booster (50 ml + 10 ml of booster, so 6 times more liquid than the booster on its own), or 3.3 mg. Unfortunately, this is not the best method, given we want to obtain a precise measure of nicotine.
So let’s work backwards. Let’s imagine we want exactly 5mg/ml, starting with our 50 ml base. This is how you calculate: divide the nicotine strength of the booster by the desired strength, so in this case 20/5 = 4. This means we will want to remove 4 ml of the base liquid (0 mg) and replace it with booster liquid (20 mg).
Given the bottle is 50 ml, you will need to remove 12.5 ml (a quarter) and add the same amount of booster liquid. In this scenario, our total volume of e-liquid with nicotine will be 50 ml, rather than 60 ml in the previous method. The advantage of this method is that we can work with bottles that are full, given we are removing and topping up rather than just adding to the base. The drawback is that flavour is a little diluted.
You can also calculate the booster quantity required for the total (50+10) but then it gets a bit more complicated and that’s why we have online calculators: here or here for example. Keep in mind as a reference that the TPD limits nicotine to 20 mg, in boosters or flavoured juice. This means that will always be the nicotine strength you need to dilute.