Hopefully by the time the Graduate had his abbreviated career counseling session, the chemistry of the material in question had evolved from its 1937 formula; in this ad, the manufacturer proudly cites formaldehyde as an ingredient. Who cared if perishable [ahem] foods were surrounded by such noxious stuff—it brought "beauty and permanent color" to the appliance.
A digression: The proofreader in me insists on noting that while the boast of ten Plaskon parts are in every fridge, I count only nine arrows highlighting the feature.