We also are excited - it's a major improvement for us. We are re-investing our profits into machines to produce some of our own formulations.
Ascorbic acid (Vit. C) is water-soluble, not fat soluble and it has difficulties penetrating oils. Water and oil do not mix unless you add an emulsifier. Most creams actually contain an emulsifier.
The most efficient way to use vit. C serum is to apply it to your skin, wait for it to penetrate and then apply any cream you like. I acknowledge that this method is quite annoying and time consuming.
You can mix vit. C into your cream but first dissolve the powdered crystals into a tiny bit of water. Mix the water into the cream. Basically, pour some of your prepared vit. C serum into your cream. For this purpose, make the vit. C serum more concentrated (add more vit. C).
We now sell a very finely-grained ascorbic acid instead of crystals so it will dissolve even quicker. Finely grained vit. C powder may even dissolve in a cream without pre-dilution in water (it depends what the cream contains). You have to try it on a small sample and stir a lot. It will take some time to dissolve. If it doesn't dissolve in the cream, use the trick with dissolving it in a little water before adding it to the cream.
The best is to use a small empty jar. In the jar, mix some of your cream and some of the fresh, highly concentrated vit, C serum (or add vit. C powder if it does dissolve). Use it up within one week (approximately) and prepare a new one. Keep vit. C serum in the fridge or prepare a new one every time you make a new batch of cream.