I use the ascorbic acid powder (vitamin C) from micro ingredients. I got a 1.1 lbs bag and I use it to make my own vitamin C serum. This bag will literally last probably 5 years... It takes so little for each batch. I like it because I can make a Vitamin C powder that's more concentrated than most retail ones and the other ingredients I use are all natural and super beneficial as well. Some words of advice: Make sure to stick to proper measurements. Adding more powder won't be any more beneficial and will song the neck of of your face doing more harm than good. I do not use a preservative so it's stored in an amber cooked bottle in the fridge and I always discards unused products after 2 weeks, even if there is no discoloration of weird smell... Better safe than sorry. I put a label on each bottle marked with the date its do be discarded so I don't lose track. But 9 highly recommend this for anyone comfortable making their own skin care products. It's made a huge difference in my Complexion!