Hoop And Bag Cover

The cover consists of a transparent polyethylene bag, supported by two or three plastic rod hoops that are secured to a rectangular or square base (Fig. 1). The physical support and protection is provided by the base and the hoops. The base should be at least two inches bigger than the specimen dimensions on all sides. The size of the base determines the size of the hoops, which in turn, determine the dimensions of the polyethylene membrane or bag. If the system is completely sealed, it can protect against airborne pollutants, rapid environmental changes, and insect pests.

Figure 1. Components of the hoop and bag cover.

• Dental floss
• Polyethylene foam plank
• Polypropylene welding rod
• Polyethylene sheeting
• Tacking iron
• Utility knife
• Wire cutters

1. Cut a piece of polyethylene foam plank that is 2in larger than the specimen on all sides.
2. Cut two or three lengths of polypropylene welding rod that are long enough to form hoops over the specimen, and to be inserted 1in into the foam. Two hoops provide adequate support; three hoops provide more stability (Fig. 2).
   
   
   Figure 2. top, Two-hoop structure. bottom, Three-hoop structure.
3. Insert the ends of two of the rods in each corner of the foam support to form two intersecting hoops. A third rod can be placed in the center of two opposite sides of the base to form a third hoop. Hoops should intersect at the top center.
4. Tie the hoops together at the top with dental floss.
5. Drape a section of the polyethylene sheeting over the hoops and fold it along the hoops to form a close fitting cover.
6. Staple the plastic along the lines formed by the hoops at 1in distance from the hoops.
7. Remove the stapled cover from the hoops and cut off the triangle of excess polyethylene along the stapled seams.
8. Remove the staples by cutting the plastic parallel to the previous cuts. If a number of specimens are the same size, this cutout may be used as a template for other bags (Fig. 3).
   
   
   Figure 3. Pattern for bag used with two-hoop support.
   
   
9. Hold the cut edges together and use a heat sealer or tacking iron to weld the seams of the bag.
10. The bag may be fixed to the polyethylene foam plank with poly-propylene welding rod pegs.

If pest control is an issue and the system needs to be sealed, the bottom edges of the bag can be sealed to the polyethylene foam plank with a tacking iron, although this is not a reversible method.