A water hole paper defect happens at the paper mill during the manufacturing process. Because of the high humidity, water droplets sometimes form and drop onto the web of paper. A hole will form and it will be seen in the sheet or web.
Offset printers sometimes mistaken these holes for a slime hole. However a water drop hole is distinctly different.
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| The difference between a slime hole and water drop hole. |
Notice the picture above on the left hand side. It is a hole, but has discolored edges. The bacterial slime has caused these outer edges of the hole to have this distinct look.
Now look at the hole on the right. This is a water drop hole. They are generally very small and do not have the decayed and discolored look on the edges.
Paper machines have cameras placed throughout. These cameras are designed to find such water drop holes and take pictures of them for troubleshooting. Here are some pictures.
To a paper mill, identifying this paper defect makes a world of difference. It is important to identify it properly to make a claim to make any kind of claim against the paper manufacturer.
What makes matters worse is if these water drop holes are present in the offset sheetfed sheets or web press rolls and they cause downtime. Perhaps even a smashed blanket. These things can be claimed back from the paper companies if evidence is found. The problem is that such a tiny defect is usually destroyed in the process.
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