Think I must be doing diy wrong but I make each concentrate separately, then add certain amounts of each together to make the flavour I'm after. I just make a note then of how many ml of each flavour needs to be used to make 10ml, 20ml and 50ml of that flavour.
Working out how much I need when flavour 1 recommended %age is 15%, flavour 2 on its own should be 7% flavour 3 needing 12% when at its own etc etc etc, that just seems too much faff to work out
I am a huge advocate for the K.I.S.S principle,few drops of a concentrate added to a 50/50 PG/VG 2 ml in a tub,add another couple drops of different flavour,taste,add next flavour & taste etc.This method means IF the result of adding flavour 2,3 etc makes it vile the waste is minimal.
Converting drops to percentages requires a couple of taste tests,when I can taste the abundance/lack of a flavour & adjust accordingly,once converted to all percentages a 10 ml bottle is produced with nic added too,vaped straight from the mixing bowl & if it isn't quite as it should be,stuffed in a drawer for a steep.
There aren't that many juices I've created from imagination,I tend to go "clone recipe" hunting or read/listen to a juice review where they say they can taste "citrus/menthol" or whatever & this is where I require the services of the little tub & a couple ml of PG/VG.My take on Snake Oil(despite never tasting the real juice)was by guessing the ingredient percentages+a clone recipe(which was where I discovered that there are 2 types of Snake Oil,USA & UK versions)& I actually prefer the UK version(which is all guesswork)to the USA version(clone recipe)
I've also noticed how over time,my tastes have changed.I switched to vaping & avoided tobacco flavours staying with fruits,menthols etc but a year later,I find myself now creating concentrates from tobacco & mixing these with just about my entire collection of other concentrates before deciding that there aren't that many other concentrates still taste vapable once tobacco is added.Caramel & Butterscotch (though tasting reasonably similar individually) when tobacco is added,the Butterscotch tasted like the vile "morning after" vomit in the back of the throat,but Caramel+tobacco was so nice,the 10 ml I mixed vanished in 1 day.
Nowadays,I find myself changing flavours several times per day whereas I used to stay with a flavour until the bottle was finished,as I'm bored with custard/banana & variations of these,fruits have to have a mystery taste or I'll not even vape an RDA worth.I have close to 100 recipes now on my phone,yet rarely mix them as they just don't give any satisfaction.There are some exceptions though,Honey+Cream was taken out the steeping drawer & placed ready to go in the trash a week or so ago(I need to build up to binning things as I despise waste)but yesterday,I needed a juice to soak the wicks of a different type of coil(only slight change to the ohms)so grabbed the Honey+Cream.The flavour was really nice,& gives me great satisfaction(as the 10 ml still has about 5 ml even though I've also been using it all today)so it has been saved(steeping since 16.7.14)and I'm going to be mixing another bottle sometime soon.