Whats does the vinegar or lemon juice do? You talking like the lemon juice from grocery stores that come in a plastic lemon?
YOU need to read the
vinegar thread

Really..anyone interested in diy should be reading this one....
I like many of Capellas flavors too but I think that everyone should know that some of their flavors do contain diacetyl. They were tested by Kimerpuff at OSDIY last year and found to be in their flavorings. Some folks don't mind diacetyl but everyone should know what they are vaping. See post # 14 here
http://www.e-cigarette-forum.com/forum/one-stop-diy-shop/240607-cant-say-enough-good-things-2.html
Well, this could be sour grapes (not saying it IS, but I've seen no documentation), or it could be that one of the chemicals used in ALL custard flavors that replaced diacetyl (sorry, can't remember the name offhand, but I'll try and find it) I read somewhere can, after a long period of time somehow develop trace amounts when tested. Again...I read it, remember it, but can't remember where. In that case, your only choice would be to not vape ANY custard flavors...which of course is your right
Bostonboxers can I ask what percentage of PG/VG do you use normally? You said you add the lemon juice to the custard mix too? By how much? Do you use a sweetener with it or just the 10% custard? How many drops of lemon juice would you put into the juice?
I should explain myself better for clarity sake. The very first flavors I tried was like 12 FA ones. For two or three weeks straight FA ones only. I then moved on to trying some of the others and now Capella's so just that part would help you understand perhaps why I still haven't tweaked this to 100 percent perfection. I really like the custard but I want to use less of it (hopefully the ten percent as a standalone) so please give me exactly what you do- thank you.
PS: OK sorry I see you said you rarely use sweetener sometimes a little EM. OK How long does it have to steep then for you a little or days?
Sooooo many questions?! lol! Sorry...I'll try to answer, but if I miss any, let me know or pm me.
For custard type flavors I use apple cider vinegar, not lemon juice. I also use a natural acv, but I don't think it matters. Usually 2 drops (large pipette dedicated to vinegar) per ml. If I'm happy with the flav right off the bat, I use ONE drop per ml only. If after using 2 drops/ml I'm still not happy with it after a week or so I'll go one more drop per ml for a total of 3.
For fruit flavors (and anything with a 'sharp' rather than 'smooth' ie, cola...) I use the same formula, but I use lemon juice instead. As for brand, I've used the frozen minute maid, and the stuff in the lemon shaped bottle. Doesn't matter to me as long as it's 100% lemon juice.
Cap Van Custard is soooo tasty, but weak when mixed. I wait at LEAST 3 days before vaping. I'll taste after an overnight steep but not vape. You'll be amazed at the difference from when you first mixed it

Same with the cheesecake. I don't do baths, cap off, or anything special...just wait a few days. I mixed a 50 ml bottle when I first bought the flavor (back when this thread started) and I'm still vaping out of it. I vape lots of flavs throughout the day and switch around a lot, but the cvc is my goto...can't stop vaping it, aaaand, to me it gets better every time I dip into that bottle (amber glass if it matters to ya).
Did I get em all? lol!
added: oh ya...pg/vg...not sure! I mean, I don't know how to figure it. I get 100ml nic in pg, mix with pg to 36 for storage. When I mix down to 24ml (I add flav to this too, so that takes it down a bit) I use straight vg so ???
Added:Here's the info on diacetyl I refered to but couldn't remember for those that care to read it