Inherent Curl

We all know what paper is made of and being of a natural product it will react to different situations in its own way, rather than a synthetic product which will react in the way it is told to react. Therefore, in some paper you will see what is known as an inherent curl and this can happen either in production or in the way it is stored so mach sure you avoid curling your paper by choosing high quality produced paper and storing it correctly.

Inherent curl can happen when the paper is being made as the fibres on the wire side of the machine will be more aligned than the paper fibres on the felt side of the machine and as such, the fibres are aligned at different degrees.

This leads to built in stresses in the wire side of the paper when it dries and it is more likely to shrink than the felt side. Then, as soon as the paper is sheeted or covered, it curls with the grain edge, bending towards the wire side. Also, if the two sides of the sheet of paper dry unevenly, when the paper is being calendered, the wetter side will stretch more and the result is a built in curl.

However, paper can develop an inherent curl long after production if it is stored in a roll for a long period of time. The curl will also be stronger and tighter in the centre of the roll of the paper. When storing paper wound up, the outer side of the sheet is under more tension and as a result will be permanently stretched.

This latter type of curl is often called mechanical curl and we have all seen it when we roll up a poster or a piece of paper and then go to unroll it. We stretch it out and roll it back the other way but it will never be smooth or flat in the same way as the fibres have moved and changed over time.

For more information and advice about stopping your printing projects from curling, contact Print Compare now.