In most cases, epoxy has a small amount of solvent in it to create the desired viscosity. Over time, this can evaporate leaving very little 'solution' to the material. It is usually a highly unusual alcohol. Also, epoxy has a shelf life of usually one year or slightly longer. You would be better off catalyzing the product and disposing of it. You will likely find that the material will 'flash' very fast, get extremely hot (300F) and will not afford you the good wet film capabilities for application to the model. Hope this helps!