Answer: We make our poster sleeves from three different types of material. Each material has significant properties that you should consider before you choose the correct one for your needs. An independent lab has tested our Polyethylene, Polypropylene, and Polyester materials for their acid-free and “safe for long term storage” properties. All these materials are inert, which means there is nothing in them that can transfer to the stored item and cause damage to it.

1. Polyethylene Sleeves– Our 100% pure-virgin Polyethylene is a soft, clear film that has some stretch to it. We stock three thicknesses of polyethylene sleeves for comics – 2mil, 3mil, and 4mil. 2mil is the thinnest and highest in clarity. Polyethylene material is an excellent choice for long-term storage as it can store at higher temperatures, a good material for chemical resistance and has a very low moisture absorption rate. https://www.bagsunlimited.com/category/6/comic-poly-bags

2. Polypropylene Sleeves – These 1.5 mil sleeves are super high clarity. The material is crisp with a high sheen. We use bi-oriented polypropylene which means that when the material is made, it is stretched in both directions, so that over time, it will not pucker (decreasing the clarity) as some polypropylene sleeves do. The super-high clarity of this sleeves and the reasonable cost make it an excellent choice for comics that are on display or being resold. https://www.bagsunlimited.com/category/6/comic-poly-bags

3. Polyester– Is considered to be the ultimate material for archival storage. It is crystal-clear, semi-rigid, and in accelerated aging tests, shows no breakdown of the material for over one thousand years. We use DuPont inert Melinex® or a suitable equivalent.  Storing comics in polyester is the equivalent of using museum-level preservation standards. https://www.bagsunlimited.com/category/353/comic-mylar-polyester-sleeves