Originally Posted by
Dragonfly /img/forum/go_quote.gif vitamin C is highly unstable though. Once it is exposed to the sun it is useless.Therefore, always use it at night.
Also, make sure it comes in a dark opaque tube that sunlight can't penetrate.
And the opening tube the tube should be very small - the solution needs to be squeezed out, then tube is closed with a small cap.
Also, look for a smaller sized tube. Once it is opened, used daily until finished.
Saving it for a once in a while application will probably render the active ingredients useless over time.
There are 3 kinds of Vit C derivatives that are more stable than the regular ascorbic acid. They are more expensive but stable:Ascorbyl palmitate - oil soluble
Magnesuim ascorbyl phosphate - water soluble
Tetrasubstituted lipophilic ascorbates - next generation
Vitamin C derivatives: skin benefits of ascorbic acid without the downside
I've seen some DIY serums using both L-ascorbic and MAP out there. Lots of good reviews. I've not tried it nor used any vit c products yet. The key is to make small batches and keep cool dark location like med cabinet.
I wouldn't buy a product that says it has vitamin c that is packaged in a clear container tho.