Alginate is a great product only in certain conditions. You must maintain a stable field (moisture, temperature, humidity). If you are going to change any of those variables then you had better not use it. As for stability, it is really only there for 24 hours under constant conditions. If you are looking for something more stable then look into PVS or VPS (polyvinyl siloxane). This is what dentists use to make stable impressions that can last a life time. PVS comes in different viscosities so you can let a light body that flows easily or a heavy body that is stiff. Usually a llight body is flowed onto the surface and then followed by a heavy body for the "filler". These do not have to be maintained in a wet field either. Not sure you can get PVS on the open market....I have access to it by trade and it works wonders at craeting duplicates of pour items.