Why is it important to control the humidity in the printing industry?

Paper is a hygroscopic material that tends to reach a condition of equilibrium with the temperature-humidity conditions of the surrounding environment. Any changes in temperature and humidity can cause dimensional variations and loss of paper flatness.

If humidity and temperature are not appropriately controlled, it can lead to printing defects or unwanted machine stoppages due to incorrect paper feed.

What can be done to decrease printing defects?

1. Paper’s absolute and relative humidity values should be known in order to ensure the right conditions during all stages of storage and subsequent printing and finishing of the product.

If there is a significant difference in temperature between the paper storage area and the area where the printing machinery is located, the paper needs to be kept close to the machine for a few days before unpacking it, so it can adapt to the ambient temperature where it will be used. In general, a time of at least 24/72 h is recommended.

2. Temperature and humidity conditions should be kept constant and controlled within a defined range to ensure efficiency, quality and reproducibility of the printing process.
   Generally, ambient temperature is kept at around 23°C, while the best relative humidity level is between 55-60% for offset printing, and between 50-55% for other types of printing.

Air conditioning, heating, air flow taken in by printing machinery, opening of doors and windows – all these processes affect the temperature and humidity and require a handling unit such as humidification system.

Nadiia Tuzova, Verso Solutions Corp, www.versolutions.ca