Advice on Paper Absorbency

There are many more things you need to take into account when choosing paper for your next printing project than just the size and the colour. For example, did you know that different types of paper and differently manufactured have varying degrees of absorbency and as a result, will absorb more or less of the ink your printing project is made up of.

The absorbency of paper is related to how much or how little it will take to water or in some cases oil, and as such this also includes the inks you are printing with, or the water used in offset lithographic printing. The absorbency of paper is related to its sizing as sizing is the process where paper is rendered resistant to water penetration.

Ordinarily, cellulose fibres are receptive to water and when made into a sheet of paper, they create a porous product, which is very absorbent. This unsized paper has the same characteristics as blotting paper, and cannot be printed on because the ink feathers through the fibres.

However, when these fibres are treated with the right chemicals, they become partly water repellent. This can be achieved by dispersing rosin into the paper’s fibres while they are still at the pulp stage, and this is called internal sizing. Aluminium sulphate, also known as simply Alum, is used as a fixing agent to adhere the rosin to the cellulose fibres. It also acts the control the pH at which the paper is made and this in turn has a significant impact on the printing quality of the paper.

Synthetic sizing agents such as AKD or ASA are more commonly used now, but your printer should know the sizing process of the paper you have chosen for your printing project and the effect this will have on your finished product.

For more information about the absorbency of papers and how this can effect the quality of your printed projects, contact Print Compare now.