There are many times when it is advantageous to have an airtight, or nearly airtight, container. From hobby collecting to displaying treasured items, a plastic container that prevents the constant contact with air and, more importantly, airborne contaminants, is greatly desirable. Many times such containers are expensive; however, you can make a container at a much lower cost.
Select a box for your project that is of sufficient size and has an adequate lid (or base) for access later on.
Test the fit of the lid to the body of the box to determine how much silicone will be required. Keep in mind that the box must seal and that most lids have certain designs to allow a secure fit against the body of the box.
Apply a bead of silicone around the lid in the groove into which the body of the box will fit. Wipe away any excess silicone that may detract from the overall appearance of the display unit.
Allow the silicone to dry, or cure. Follow the manufacturer's recommendations regarding this to allow sufficient dry or cure time.
Test the seal to see if adjustments need to be made. Look for areas where the lid will not seat fully against the body of the box. Use a knife or hobby knife to carefully remove excess or unwanted silicone.
With Rubber Stripping or O-Rings
Test the O-ring or stripping in the grooved channel of the lid where it will seat against the body of the box. Make sure there is enough room for the lid to function and attach.
Apply a small amount of adhesive to the groove of the lid. Do not overapply and also don't get adhesive on the outer portion of the lid.
Insert the O-ring or stripping into the groove of the lid, and use a blunt-tipped instrument to firmly press the ring or stripping into contact with the adhesive. Allow the adhesive to dry completely.
The key is to create a seal or seat around the groove of the lid that will seat snugly against the body of the box and thus prevent air from entering the box itself.
Use care when applying silicone and adhesives. Wear proper eye and hand protection. Use extreme caution when working with sharp tools and particularly knives. Read and understand all manufacturer's instructions.