1st timer, ratios, and math questions

[Pedrobear]

Now that Im pretty happy with my hardware, I would like to venture into cutting my costs even more with DIY juice and before I buy, I wanted to ask some questions if that's ok... I know we have handy calculators out there, but I would like to know the hard math / calculations etc..,

Shooting for a 70/30 VG mix at 6mg 10mL bottle for example...

So, juice is VG+PG+Nic+flavor. Understood. I prefer my juice a higher VG then PG. If I were to buy say 60mg 60mL VG base nic, do you dilute right into your final mixture or can you "pre-dilute"... IE.., 6mL of nic to 94mL pure VG would net me 100mL of 6mg nic unflavored, yes? I could then use this mix as my nic/VG? So I would combine 7mL of that already made juice, and 3mL of pure PG, to net a 70/30 6mg nic unflavored solution? Now, to add flavor, I could use 7mL of that pre made nic/VG, 2mL of PG, and 1mL(2x .5 mL, 3x .33mL etc..,) flavorings? Is this general math / idea correct? If not, could you please steer me to hard formulas that could steer me correct?

Im after a vicks type menthol blend, no "extreme ice, wintergreen, etc..," just pure menthol main flavor, with small hints of different fruits I enjoy. I want to get the menthol part down. Im not quite understanding the whole menthol crystal and pure grain alcohol mixing... Nor do I understand why the calculators have a water option.. Im assuming bottle water would be the best? (Disani, aquafina?)

Thanks for reading and any help or knowledge you could provide!

 

[Boletus]

There are a few spreadsheet calculators you can download that will greatly simplify the math, including one mentioned in the stickies here:
http://www.e-cigarette-forum.com/fo...e-calculator-added-quantity-calculations.html
There are others that may be better, but IDK since I do not use them.

The general formula for concentration of a single substance in a mix is:
sum(C_iV_i)=C_fV_f, where:
C=concentration of that substance (e.g. mg/ml),
V=volume (e.g. ml),
"i" refers to each liquid being combined (e.g. for the first liquid, i=1, for the second, i=2, etc), and
"f" refers to the final mixture when all of the "i" liquids have been combined.

Note that for simplicity, the volume occupied by the nicotine is usually ignored, because actual nicotine volume is usually less than 4% of the final mix. You can include it if you want, but it gets very complex and will not do you much good, except the mental exercise. As long as you are consistent, the easier way works well enough.

So for example if I mix 10 ml of a 70% VG 30% PG base with nicotine concentration of 100 mg/ml with 20 ml of straight VG, my nicotine concentration is given by:
C₁V₁+C₂V₂=C_fV_f
=(100 mg/ml)*(10 ml)+(0 mg/ml)*(20 ml)=C_fV_f
and we can calculate V_f because it is V₁+V₂
V_f=10 ml + 20 ml = 30 ml
Solving for C_f:
C_f=[C₁V₁+C₂V₂]/V_f
=[(100 mg/ml)*(10 ml)+(0 mg/ml)*(20 ml)]/(30 ml)
=[1000 mg +0 mg]/30 ml
=33.3 mg/ml.

Now you can calculate the VG% the same way:
(70% VG)*(10 ml) + (100% VG)*(20 ml) = C_fV_f
V_f= 10 ml + 20 ml = 30 ml, so
C_f = [(70%)*(10 ml)+(100%)*(20 ml)]/(30 ml)
=(700+2000)/30
= 90%

So now when you add flavoring, you need to do the same thing for it. Note that when you add flavor, the nicotine and VG concentrations will change, so you need to do the same for them again to get precise final concentrations. Or you can also include the flavoring in the original equation, where now you have:
C₁V₁+C₂V₂+C₃V₃=C_fV_f
Of course now you need an iterative process to determine how much of each is needed for a given final concentration of each substance.

So in summary, if you are good with algebra, enjoy math, and completely understood all of the above, that is how to do it. However, if that is not the case, use a calculator application.

 

[Stosh]

Pre-mixing a larger batch of unflavored nicotine and PG/VG is a simple way to go. If you like you can mix it for one or two mg/mL higher than you vape so when you add flavors it drops down to your desired level.

Mixing pure menthol is easier still, mix you PG/VG/nicotine to whatever you want to vape, the amount of menthol you will need to add is negligible. To mix the crystals I fill a 5mL bottle with crystals, as much as I can fit and add PGA or vodka, then shake like heck. The results are strong enough that a few drops is all you need for a 15 mL bottle.