Double-Jar System for Types in Fluid Collections

This system consists of two jars, one inside the other (Fig. 1). The inner jar contains the specimens. Two polyethylene foam rings divide the space between the jars into three sections, thus providing three security chambers to prevent evaporation over time.

Figure 1. Three versions of the double-jar system.

• Compass or machinist dividers
• Polyethylene film or polyester film, 0.08mm thick
• Polyethylene foam, laminated between two layers of polyethylene sheeting, 1mm thick (for use with jars with metal lids),
• Polyethylene foam sheeting, 1cm thick
• Scalpel
• Two glass jars (one should fit easily inside the other)
  
  

1. Choose two suitable jars, one should fit easily inside the other (Fig. 1).
2. Measure the inside diameter of the outer jar and calculate the radius (Figs. 2, 3).
   
   
   Figure 2. Measuring inside diameter of the outer jar.
   
   
   Figure 3. Calculating the inside radius of the outer jar.
   
   
3. Using a compass set to the calculated radius, mark the circumference on the polyethylene foam sheet (Fig. 4).
   
   
   Figure 4. Marking the inner circumference on the polyethylene foam plank.
   
   
4. Cut the disk with a sharp scalpel. Repeat this operation to obtain the second polyethylene disk.
5. Measure the outer diameter of the mouth and the middle of the inner jar, and calculate the two radii (Fig. 5). 
   
   
   Figure 5. Measuring outer diameter of inner jar.
   
   
6. Trace one concentric circle based on the radius of the middle of the jar onto one of the pre-cut disks; trace another concentric circle based on the radius of the mouth onto the second disk.
7. Cut out the central disks to form the rings (Fig. 6). One ring should fit the mouth of the inner jar, and the other ring should fit the middle of the jar.
   
   Figure 6. Polyethylene rings and jars for assembly.
   
   
8. Position the specimens in the inner jar in the opposite direction than normal placement, and fill the jar with preservative to the rim.
9. Dry the mouth and the rim, fit it with a sheet of polyethylene or polyester film and seal the jar.
10. Put the first ring in the bottom of the outer jar.
11. Cover the inner specimen jar with the inverted outer jar, pressing the mouth of the inner jar into the central opening of the ring. Turn the entire assemblage over into final position.
12. Fill the outer jar with preservative, at least two-thirds full.
13. Position the second ring around the middle of the internal jar.
14. Fill the outer jar completely, dry the rim, fit a piece of plastic film over the rim, and close the jar.

If the lid of the outer jar is metal, it can be fitted with a disk of laminar polyethylene / polyethylene foam/ polyethylene to prevent corrosion.