Short Answer:
Yes; as nicotine oxidizes it can become more harsh/unpleasant. Oxidation is accelerated by heat, light (UV light), and exposure to fresh air. Reduce those elements and you slow oxidation.
Long Answer:
Potential problems in mixing:
- Over-filling mixing bottle: This is particularly problematic when adding ingredients directly into the end-use bottle (vs. using an intermediary container like a larger bottle or beaker). Thick liquids, plus limited range of motion, equals poor/ineffective blending. The result is incomplete blending, poor flavor distribution, and potential nicotine "hot spots." (Note: hot spots will be harsh) Best practice: leave enough room to thoroughly mix.
- Under-filling aging bottle: An over-sized/under-filled bottle leaves addition air in the bottle, which in turn leave additional oxygen, to react with the nicotine. Best practice: leave only enough room to thoroughly mix.
- Excessive mechanical mixing: the use of any form of open container power mixing (e.g. blenders, frothers, stir plates, etc.) all expose the mixture to more air/oxygen than closed-bottle shaking. Closed bottles have a finite amount of available oxygen. Extended mixing cycles, and repetition of mixing cycles, expose the liquid to more oxygen. Best practice: mix only as much as needed to thoroughly mix.
- Environment: Warmer, brighter environments are going to encourage faster reaction (oxidation) than cooler, darker environments. Artificial sources, such as hot water baths or hotplates, accelerate the reaction. (Have you ever left a bottle of e-liquid in a hot car for a day?) Best practice: don't apply unnecessary heat or light.
- Patience: Failure to give a mixture enough time to blend/stabilize/homogenize. How much is "enough" is dependent on specific ingredients used, and personal preference. Best practice: vape a sample... if it is enjoyable; vape away... if it is not; put it away for a while, then sample again. Repeat as needed; or until no further change is detected. Then evaluate the recipe for change or abandonment.
So, looking at the above, one can start to see potential conflicts of interest. This is why there are so many different ways people choose to DIY. It becomes a matter of give and take. Benefit vs. risk. Personal choice.
I have noticed a reoccurring theme in your DIY threads... "smoothness." So, I went to your profile page and looked at all the threads you have created. Of 40 threads created, 5 (including this one) are smoother DIY related, and 35 are hardware and coil building related.
There is nothing wrong with that, and I too, like to experiment with different hardware. However, in
my opinion... if you are jumping all over the map with hardware, coils, wire, and whatever else, you are not going to find satisfactory answers to your DIY questions at the same time. It is like trying to figure out why your gasoline isn't performing the way you want; when you are driving everything from lawnmowers, to land-speed vehicles, and everything in between.
Many folks find, when switching from their eGo starter kit that used classic CE2 cartomizers (or something similar), to their first sub-ohm DTL rig; their juice that was "just fine" before, is now no longer pleasing. Nic levels are too high, flavors don't taste the same; something creates the need to change up. Vaping DIY does not make us immune to the effects of changing hardware.
If you haven't already; find a setup you are comfortable and confident with. Then make that setup your DIY rig. Use only that rig, always in the same configuration, to test your DIY experiments. And when you do; focus on
only one thing at a time. Making multiple changes, adjustments, and substitutions, confuses the results. Including hardware changes just makes identifying cause and effect even harder.
In
my limited experience, the only way
I can make any sort of productive advancement in
my DIY efforts, is to maintain
consistency in my hardware. That means using the same atomizer, same coil configuration, and same wicking configuration. Because the same liquid, can and often does, vape differently in different setups.
Play with exotic hardware all you want; just don't do it with your DIY. Or, at least don't evaluate your DIY, while you do it.
When you ask "is it better to add nicotine before, or after aging?"; I have read answers supporting both. Is one right and the other wrong? I don't believe so. I believe that each person has found what works best for
them. One or the other, or both, or neither may work for you.
The only
real way to know
your answer is to set up a simple test. Mix two identical batches (they don't have to be big), except leave out the nicotine in one. Treat them exactly the same. Age them for whatever time you choose. Then add in the nic to the one missing it, mix well, and vape both samples side by side. Which do you like better? That is how you find
your answer.
Slow, steady, and methodical, is how the greats succeed. Patience is your best friend!
I hope you find the success you seek.
