Sweet summertime – ahh… the season that (most) people look forward to. Sun, warm temperatures, vacations, break from school, etc. But the heat and humidity that summer brings can be a game changer when it comes to paper products.

As the temperature in the air increases, so does its ability to retain moisture. When humidity levels increase, the fibers in the paper draw in moisture very quickly, resulting in expansion. For example, think about the doors in your house and how they seem to stick during the summertime. That’s because of materials expanding due to the humidity. The same happens with paper tubes and cores.

During summertime conditions, paper tubes and cores manufactured in high humidity can shrink drastically if an end-user puts them into an air-conditioned room with extremely low humidity. Humidity can weaken the tubes and cores which will then cause them to fail. If used in a timely manner, less moisture will affect the product. Paper tubes and cores should not be stored near any type of heating or cooling unit, in an air stream of heated or cooled air or in the path of a humidifying stream of air. Knowing your storage environment is very critical.

Understanding how moisture and humidity affects paper tubes and cores is imperative for end-users as they are looking for the products to have the best appearance and performance. To ensure optimum performance, control the relative humidity (R.H.) levels and temperature in the processing and storage environments.

Being a fibrous product, cores are sensitive to changes in temperature and humidity.  To retain normal dimensions, paper tubes and cores should be used and stored at 73°F and 50% relative humidity (R.H.).  Most problems arise when the relative humidity drastically rises or falls.  Usually these changes take place during the changing of the seasons.  Air conditioned rooms, cold warehouses, low humidity and damp areas all will have an impact on the dimensional stability of fiber cores.  These are the same conditions that cause wooden doors to stick in everyday life.

Cores packaged in cartons – The cores around the outside are the ones most susceptible to change as they are closest to the atmospheric influences.  Cores on the inside of the boxes may not be affected as much because they are more protected.

Snake-laced on pallets; tied in bundles; on racks – Outside perimeter cores are likely to be more affected by drastic humidity and temperature changes, causing inconsistency between different cores.

Wintertime conditions – In severely cold weather when plant heating systems are running for prolonged periods of time, it is likely that the humidity within plants becomes very low.  These are the same conditions in one’s home that cause dry air, sinus problems, doors drying out, static electricity, etc.  These low R.H. conditions usually cause cores to shrink in size due to the evaporation of moisture from the cores.

Summertime conditions – Cores manufactured in high humidity, e.g. 90% R.H., can shrink drastically if the customer puts them into an air conditioned room with extremely low humidity.