Final answer:
A silicone and white spirit mixture can be stored without hardening if kept in a hermetic container because silicone cures by reacting with moisture in the air. To preserve an opened tube of silicone caulk, store it in an airtight container or use a commercial preservation product. The hardening of the silicone solution over time is mostly due to exposure to air.
Step-by-step explanation:
When using a mixture of silicone and white spirit to waterproof gear, the solution can generally be stored for some time without hardening if kept in a hermetically sealed container. Silicone is versatile and used in a wide range of products due to its heat-resistant and rubbery properties. When exposed to the air, silicone can start to cure due to the presence of moisture, even in very small amounts, because many silicones cure via a process that includes a reaction with moisture in the air. If the solution does harden over time, it is most likely due to inadvertent exposure to air and the subsequent moisture that catalyzes the curing process.
To increase the chances of preserving an opened tube of silicone caulk, one might try storing it in an airtight container or using a commercial sealant preservation product designed to create a barrier between the silicone and the air. This can significantly extend the life of the silicone, though it is not a guaranteed method to prevent hardening entirely. It's important to always follow the manufacturer's instructions for storage and handling of silicone-based products to maximize their lifespan.