Food Packaging Cardboard – Try This For Size

If you are looking for a box sleeve or wrap for chilled food, baked goods or a ready meal, your printer will probably recommend using a hard sized board. So what does that mean? The first thing to note is that the term “sized” has nothing to do with the dimensions of the cardboard. In the context of food packaging, to “size” means to “treat with size to glaze or stiffen”. A size is a substance that is applied to, or incorporated into, other materials, especially papers, to act as a protective filler or glaze. As well as being used in paper-making, it’s also used in textile manufacturing, guilding and photography

This addition of a “size” agent to the middle plies of the paperboard increases its resistance to water absorption and allows the board to be grease, heat and water-resistant. These qualities make hard-sized food packaging suitable for microwave and conventional oven use. A hard sized folding boxboard with a single coated white reverse is ideal for a wide variety of end-uses, including packaging for refrigerated and frozen foods.

The earliest paper was unsized, soft, pliant and absorbent, making it well suited to the calligraphic brushwork of scribes. Our first records of sizing appear in the 8th century in China and Arabia, with the use of glue-like coatings such as gypsum and starch. Today, elements such as acid- or alkaline-based rosin and papermaker's alum are added directly to the wet paper pulp, this is called internal sizing.

There are three categories of papers with respect to sizing: unsized (water-leaf), weak sized (slack sized), and strong sized (hard sized). Papers that are unsized readily absorb moisture, and are used for towel, tissue, and blotting papers. Slack-sized paper has a minimal amount of internal sizing, while hard-sized paper has a greater degree. Hard-sizing is used for papers such as packaging board stock, which must withstand exposure to significant levels of moisture. Sizing is also added to prevent glues and other adhesives from penetrating the paper when applied to labels and packaging.