Shelf Life 3.2023
Many of us are familiar with the “Use Before” dates on our food stuffs. What we may not think about is the use before dates or shelf life on the materials that we use for building models. Adhesives may age by solvent evaporation and/or polymerization of their ingredients. This can affect their strength or viscosity and create application problems. They may not properly cure and achieve the structural strength expected when used. Paints may separate, color shift, have solvent evaporation, and some chemistries may also polymerize. In addition, spray cans may leak their propellant gas over time. Like adhesives, these issues can create curing and application problems.
Typical spray paints, e.g. Krylon and Rustoleum, have a manufacturers’ specified shelf life of two to three years. A common 5 minute epoxy by Devcon has a shelf life of three years, West Systems epoxies have “expiration dates” two years after manufacture, and Titebond III has a minimum shelf life of one year. Your experiences may be different. Environmental conditions, typically storage temperature and humidity, will affect shelf life. If the storage environment is comfortable for you, it will probably extend the shelf life of your products. Also, most shelf lives are stated for unopened products. Exposure to oxygen and humidity from broken seals can shorten shelf lives. Aerosol cans, once used, are more likely to leak their propellant over time.
Some materials will allow the addition of solvents to thin them to ease application if they have become too thick to apply. Agitation to remix separated ingredients may help. Follow the manufacturers’ recommendations. The best strategy, if in doubt about a paint or adhesive, is to apply a sample to spare or scrap items and evaluate whether it is acceptable.
NAR Safety Committee Chairman