Warning: Don't be a dumbass. Know your limits. If you don't have safety equipment, protective gear, and the requisite knowledge to use them, don't handle nicotine in concentrations above 5%. Seriously. There is still no known antidote to nicotine poisoning, so "oops" may be followed shortly by vomiting and death. Also, even if not handling high-concentration nicotine, be smart. Don't mix it up in your livingroom around children and pets or in the kitchen where you mix baby formula. Being in the business I've heard horror stories. We had a customer way back who told us he had ordered l-nicotine (>99%) and was going to start his own business mixing it up in his apartment. An apartment. Let that sink in. One spill and he not only would put his entire family at risk, but also all the other tenants. And what if an accident did happen? That would put every vaper at risk. So, again, if you don't know what you're doing, don't do it.
Definitions, Sources, etc.
What Is It and Where You Can Find It
USP: Stands for United States Pharmacopeia. Simply, it is a standard against which ingredients are measured. If an item is USP, it means it is certified for compounding in a pharmacy.
GRAS: Generally Recognized As Safe. An FDA designation that a chemical or compound is safe for consumption.
Glycerol: AKA glycerine, glycerin, propanetriol, VG. An alcohol almost exclusively derived from plant matter. Available in pharmacies and in natural food stores/co-ops as well as from chemical suppliers. Food grade or USP are fine. However, be aware there are industrial and vetrinary grades that you would want to avoid. Liquid. Clear. Colorless. GRAS.
Propylene Glycol: An alcohol primarily derived from petroleum. Food grade or USP are fine. However, be aware there are industrial and vetrinary grades that you would want to avoid. Available from chemical suppliers. Liquid. Clear. Colorless. GRAS.
Ethanol: ETOH. An alcohol produced by yeast during fermentation of sugars. What most people think of as "alcohol". 95% or greater concentration available from liquor stores or from chemical suppliers. Liquid. Clear. Colorless.
Citric Acid: A weak acid that gets its name from the citrus fruits. Available from natural food stores/co-ops or from chemical suppliers. Crystal/powder. Clear. Colorless. White in powder form. GRAS.
l-Nicotine: Levorotary nicotine. Other forms of nicotine are racemic and dextrorotary (both synthetic). The levorotary form of nicotine is the "natural" form. A stimulant, nicotine is found in tobacco as well as in plants in the Solanaceae family. Available from specialty chemical suppliers or, in greatly diluted form from e-liquid suppliers. Liquid. Clear. Very pale yellow.
Distilled Water: Water that has been distilled to remove impurities and micro-organisms. Do not use "tap" water or spring water as these may contain impurities and micro-organisms that will cause off flavors to develop. Available at most supermarkets and pharmacies. GRAS.
Flavorings: Can be artificial or natural. Usually GRAS. Avoid those containing sugars (sucrose, fructose, dextrose, glucose, etc.). Available at supermarkets, natural food stores, co-ops, baking/cooking suppliers, homebrewing suppliers, and flavoring companies.
So, my favorite drink is Grand Marnier. Needless to say, since I started coming up with flavors, that was my holy grail and, as it turns out, my Moby Dick. Citrus flavors (orange, lemon, lime, etc.) are all citrus oil based. Those oils are not, practically speaking, miscible in glycerol or water. Since that's the base we used, it was impossible. Not only that, citrus oils are used for cleaning preciesely because they dissolve almost everything - including most rubbers and plastics that you might find in an e-cig tank. Or in a dropper bottle.
It's mostly heat
Back in 2010 I did expiriments with our 60 mg/ml unflavored and menthol bases, both with and without citric acid and both with and without an argon header (MAP so that no oxygen was in contact with the e-liquid). There were controls (kept in foil at -5 deg. C), ones kept at room temperature in foil and also exposed to light, and ones kept cool (winter temperatures in Vermont) but exposed to artificial and natural light.
After 60 days, the "cleanest" (least odor and discoloration) e-liquids were the controls and those that were kept at winter temperatures exposed to light. The presence of citric acid had no noticeable effect nor did the argon modified atmosphere packaging. Light had a very minor effect. One interesting feature of all samples was that the menthol bases were all more degraded than the unflavored bases. Why this occured, I don't know. Other than the difference when compared to the unflavored samples, the results with the menthol base were similar to those from the unflavored base.
Results: To keep your nicotine containing e-liquid fresh, keep it cold.
Purity and Heat Matter
We started out in 2009 using ultra pure lab grade l-nicotine (>99.997%). It degraded faster than the nicotine we were most recently using that was only guaranteed to be >99.9%. The difference? The nicotine we were most recently using was being produced specifically for e-liquid. It didn't matter if it had slightly more water, but it did matter that it had fewer byproducts of nicotine degradation and that the manufacturer kept it chilled and away from light.
For those that don't know, l-nicotine has a very distinctive odor and can range from near colorless to yellow depending on decomposition. Ideally, you want your l-nicotine to be near colorless. The smell and taste are still there, but those are the smell and taste of nicotine. The best way to cut down the smell and taste is by using an acid to convert some portion of the l-nicotine (which is a base) into a salt by adding acid. We used citric, but Ive heard of other manufacturers using ascorbic or acetic acids.
As mentioned above, nicotine degrades with heat. Therefore, because the reaction between nicotine and an acid produces heat, you want to keep the reaction cold. The easiest way to do this is to add the correct amount of acid to your e-liquid base and then chill that to -5 deg. C or below. When you slowly mix in the nicotine (which you'd be smart enough to keep chilled), the reaction will not generate enough heat to significantly raise the temperature of the entire mass and, as such, minimal degradation will occur.
Menthol and Artificial Cooling Agents
Menthol Rules; But Not In Glycerol
As a menthol user, my first order of business was creating a good menthol e-liquid. We were trying to avoid propylene glycol completely. There was just one problem: menthol is not readily soluable in glycerol or water. I spent two years trying various artificial cooling agents and they all left much to be desired. Most imparted an off taste and, those that didn't, woefully underperformed menthol in cooling. That is why our menthol had propylene glycol and ethanol in it at about 20% each.
Don't Overdo It
You may not know this, but flavor producers give a usage range or limit for their flavorings. Usually, this is between .5 and 2.5% by volume. However, I've had more people ask me about someone on a message board recommending 10% or even as much as 25% of an e-liquid to be flavoring.
That's insane. First, when creating e-liquids you are already using flavorings in a way that they were not intended. Second, the reason the manufacturers give those figures is that those are figured to be safe concentrations. And finally, if you have to use 25% flavoring, you are either using a really shitty flavoring or are using a really crappy base that has such a bad taste that it requires that much flavoring to cover up. Don't do it.
It's Simple... Mostly...
The math involved in making e-liquid is relatively simple, if you can "get your head around it". Here are some sample problems and solutions (welcome back to junior high):
Ex. 2 (slightly more complex):
Ex. 3 & Sol. 3 (about the most difficult):
You bought another liter of the 24 mg/ml pure VG base. You did the steps just like in Ex. 2 above and figured out that you can get a total of 2400 ml of 10 mg/ml e-liquid from it (1000 ml * 24 mg/ml / 10 mg/ml). You noticed the flavoring and citric acid were rather thin (like water), so you decided to treat them as water for the time being. You figured out that you need to add 920 ml of glycerol (2400 ml * .8 - 1000 ml). You then had 1920 ml of your 2400 ml total. To figure out how much Citric Acid Solution to add, you looked at the recipes page and saw that VTV used 4.54 ml of the solution for every 6 g of nicotine. Since you knew you had 24 g of nicotine, you did the math and found you needed to add ~ 18 ml of the Citric Acid Solution (24 g / 6 g * 4.54 ml). You then turned your attention to the flavoring. Seeing that it takes 600 µL (0.6 ml) of Mocha Flavoring to make 30 ml of Mocha e-liquid, you figured out that you needed 48 ml of the Mocha Flavoring (2400 ml / 30 ml * .6 ml). You then had measurements for all the ingredients except the distilled water. You added up all the other ingredients and got a total volume of 1986 ml. Subtracting that from your total volume of 2400 ml, you found you needed to add 414 ml of distilled water. With measurements in hand, you reread the hints above.
After rereading the hints above, you decided it would be a good idea to mix up everything except the 24 mg/ml nicotine base and place the mixture in the refrigerator or in the freezer where you, of course, placed your 24 mg/ml base when you received it. Once both were well chilled, you slowly mixed them thoroughly, filled your e-cig, and finally enjoyed vaping Vermont Vapor 10 mg/ml Mocha again.
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