yeah i got the special fuji apple flavour when it was out in their christmas tree bottle,   was nice.

Hope my new strawberry comes today   

Thanks guys!!!
 
I've copied all to my HD for future reference.

Told ya Rik!!!!

Welcome to The Den, Yoda75 

Here is an example. I believe you are using 12 mg/ml and would prefer 18 mg/ml.

Assume you want to make 30 ml of 18 mg/ml juice. Your nicotine base is 100 mg/ml.

You are making 30 ml of juice, so 30 ml x 18 mg/ml - 540 mg of nicotine is needed.

The most direct method is using some algebra.  You don't need to know how the algebra works, just plug new values in the proper places of the first equation  if you desire some other concentration or use different starting strengths.

(100v) + 12(30 - v) = 30 x 18  where v is the amount of 100 mg/ml base needed to end up with 18 mg/ml vaping solution
100v + 360 - 12v = 540


88v = 180
v = 180/88 = 2.05 ml nicotine base  (2 ml is close enough)
so 30 - 2 = 28 of the 12 mg/ml starting vaping juice is needed.

To check, you need 540 mg nicotine total.
(28 ml x 12 mg/ml) + (2 ml x 100 mg/ml) = 336 + 200 = 536 mg nicotine 
That come out to 17.87 mg/ml (you won't be able to detect the slight shortness of nicotine)

You can get nicotine base in various PG/VG ratios. I use 50:50 everywhere, so the actual ratio is only changed by the flavoring I add when I mix my juices from scratch. If you can get your nicotine base with the same PG/VG ratio as your juice, then the ratio will remain the same after mixing the starting juice and the nicotine base.  MFS has these ratios available: 100% PG, 75:25 PG/VG. 50:50 PG/VG, 25:75 PG/VG, 100% VG. There are other vendors that offer similar ratio choices.

A further example to show how plugging in different concentrations works. Let's assume you have 50 mg/ml nicotine base and your starting juice is 6 mg/ml. You want to end up with 20 ml of 12 mg/ml juice.

(50v) + 6(20 - v) = 20 x 12
50v + 120 - 6v = 240  (you need 240 mg of nicotine total)
44v = 120
v = 2.73 or approximately 2.75 ml of the 50 mg/ml juice.
20 - 2.75 = 17.25 ml of the 6 mg/ml starting juice is needed

Check:  50 x 2.75 + 6 x 17.25 = 137.5 + 103.5 = 241  (only 1 mg off - unnoticeable)