A customer has asked me to formulate diy face masks that she can make in store and provide to the customer to use once or twice.
I have let her know that once she makes it it would need to be kept in the fridge and used within the week.
Is this correct? It would be using kitchen items, sterile water and clay. Is there any ingredients that she can add that will make the product last longer or will say 20% clay and glycerin make sure it is ok for 1 week. Also how can I make sure it is ok without sending for micro testing?
have tried to convince her to use natural preservatives to no avail.