When it comes to the approximate proportion of glycol and water for a popsicle machine, the suggested ratio for the freezing agent is 60% food grade pure (99.99%) propylene glycol and 40% clean tap water. This ratio helps to reduce the overall cost of the freezing agent.

Propylene glycol is a popular choice used as a freezing agent due to its superior temperature-keeping properties and its non-corrosive nature towards metal surfaces. While the initial cost of using propylene glycol may be higher compared to salt water, it proves to be more cost-effective in the long run when considering maintenance and cleaning.