This is a foolproof way to preserve silicone sealants.
Silicone sealant polymerize by condensation reaction, with water being the catalyst. Once opened, the silicone in the tip is continuously exposed to water vapor and starts hardening. Different methods of stopping this process such as aluminum foil, plastic food wrap, nail or golf tee closing off opening, etc... were tried unsuccessfully. A tube cap or tip cap will still result in hardened silicone after a month. This is because a hermetic water vapor seal with the above could not be achieved once the tip is punctured and polymers do have minute air permeability (hence the aluminum foil seal in cartridges opening).
Using a hydrophobic liquid would provide a dry environment to preserve the sealant and create an instant seal. Mineral oil has been used successfully for this purpose.
1. Find storage container big enough to hold tube or cartridge and mineral oil. A puncture resistant plastic bag will also do (minimizes the amount of mineral oil needed).
2. Put silicone in container and pour enough mineral oil to cover its opened tip.
3. Close container. If using a bag, put it in an open container with tip down so as to have the tip covered with liquid.
Tips & Warnings
1. Clean tip well before using or extrude some material before use because any mineral oil film on the silicone will hamper moisture absorption and inhibit hardening.
2. This method should preserve the silicone sealant until expiry date.
