Thanks for all the comments and please don't take mine as criticism, I just can be kind of obtuse when on a "quest".
I am not a DIY'er but when I went to Tasty Vapor, they told me to let the juices steep. I can say there is a huge color difference in them. I didn't try them out of the bottle and let them steep for over a week before vaping. I'm sure there is some sort of chemical reaction going on that certainly affects the coloring, so I'd imagine it probably does for the taste too.
Somehow the amount of oxidation that occurs dues to the very limited amount of air trapped in the bottle wouldn't seem to be significant in terms of taste.
So what's the chemical reaction that makes stew taste better the next day? I have some liquids I haven't used in a long time, I haven't opened the bottle since when I first got them, and the liquid definitely looks darker. Why is that? Maybe evaporation, even though the bottle has been closed?
Remember we're talking foods and liquids for vaping. Just a quick analysis shows that additional evaporation occurs when the foods are reheated. That would result in a concentration of the flavors already present. Steeping is generally done with the lid on so no evaporation of any significance can occur. Some oxidation probably does occur because of the air trapped in the bottle.
One company that I get my liquids from make-to-order (Mr-E-Liquid). They include a card for each flavor instructing how long to let it steep. One example, Pure Michigan. When it is delivered, it's crystal clear and you can faintly smell the blend which is apple and strawberry. The card reads to let it steep in a dark cool place for at least a week and also on that same card.. that the color will change to a deep golden color. This is a 33% vg custom blend. After that time period it smells heavenly and it is a slightly sweet tasting exactly like fresh apples and strawberries, no artificial taste. So... in that case... steeping serves a purpose. I get a lot of my liquids from them.
I wonder if they can provide some support for their steeping instructions, other than "it needs to steep to taste right". A cool, dark, place would inhibit most chemical reactions...just sayin'.
Good Evening DIYers,
I also find that steeping or letting juice mellow does affect the color and flavors. I think that some of the PG evaporates, leaving a mellow product. If the cap is left on, this probably will happen very slowly, but if the cap and little nipple is left off, PG will evaporate. Those of you who use 100% VG? Who knows? My problem is I I just can't wait, and so far my DIY is just OK. Nothing yet to beat the premixed flavors that I love.
How does the PG evaporate and that would change the ratio of PG/VG as well. Leaving the top off will, over time, concentrate the flavors as the water molecules evaporate but the same thing can be accomplished much more quickly with a little heat.
I think steeping is the wrong word when talking about e juice. I think age or marrying is more appropriate. Kind of like a gumbo is better the second day (those from Louisiana will understand).
Again, reheating a food the second day, like gumbo, chili or spaghetti sauce (or any dish containing a lot of liquid components) is far different than letting a liquid sit in a cool, dark, place in a sealed container. In the case of foods, the amount of water is reduced by reheating which concentrates flavors.
On the steeping conundrum, and whether there is a measurable molecular change taking place: I haven't noticed any actual improvement in the liquids I use as they age, and there are a few that become decidedly unfriendly to cartomizers and clearomizers when they age more than a couple of months.
On the other hand, sweet tea (southern style) is always noticeably better after it has resided in the fridge for 8-12 hours. It seems to blossom, flavor-wise. I've often wondered if there's more to it, than simply a melding of the tea and the sugar.
Melding, at least to me, means thorough mixing. I guess some of the molecules could become sort of "bound" together, but I've never seen any real "proof" of what is going on. I'd love to know for sure. Another thought about the sweet tea, is it in a tightly closed container of a pitcher with a loose cover? In the latter situation some evaporation would occur.
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joann are you up late...you always seem the last to go....bit like me...night owl.....lizzie geez I hope your warm....oh sorry sandy....forgot to mention I like the hair do....I have thick wavey hair...I keep it long past my shoulders....is the only way for me...if to short its...a mess....I sent rabbit a photo of myself by my smart phone...also a pic of alice....I havnt got one with volt yet...I know this may sound confusing...but I don't have my email on comp...only on my phone...I have my reasons....ok night all sweet dreams....ooops sorry im posting like this.....its 
bender style
