Container Transpiration

Initial Transpiration Study

Figure 6.1 shows the rate of transpiration for 125 mL and 500 mL LDPE bottles with conventional PP caps. This study, which was conducted over a five year period, showed a significant transpiration rate difference between the two bottles. Initially, it was thought that transpiration was occurring through the container walls. However, no correlation could be found that would explain the difference of the slopes. Surprisingly, it was discovered that there was a direct correlation between the transpiration rate and the circumference of the opening.

Figure 6.1: Transpiration - 125 and 500 mL LDPE Bottles

The transpiration rate for the study shown in Figure 6.1 was found to be directly proportional to the ratio of the circumference of the bottle opening to the surface area of the solution. No correlation of the transpiration rate to the bottle surface area could be found. These findings suggest that transpiration is occurring around the cap/bottle opening and not through the container walls. This discovery was unexpected. Therefore, additional transpiration studies were conducted in an attempt to better define the transpiration mechanism.

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