A true silver colloid, which consists of silver particles and not silver ions, does not require glass bottles and are typically shipped and stored in PET plastic. PET stands for polyethylene terephthalate, a form of polyester. PET is commonly used to package soft drinks, water, and fruit juice. PET plastic bottles are the single most prevalent beverage bottle produced in the world today. High-quality products do not require a glass bottle to remain stable.
Many products which are advertised as being colloidal silver are actually ionic silver solutions which must be stored in glass. Ionic silver will potentially interact with plastic containers and cause the solution to deteriorate over time. It is generally the lower quality products that require a glass bottle to remain stable.