Submersion time: The test protocol only involved submerging the bottles for 10 minutes, which may not have been enough time for the labels to fully adhere to the bottles. Increasing the submersion time or using a different method of submersion could help to address this issue.

Drying time: While the protocol mentions that the labels were left to dry for 30 minutes at room temperature, it is possible that this was not enough time for the ink and adhesive to fully dry. Increasing the drying time or using a different method of drying could help to address this issue.