Choosing the right paper calls for a strong knowledge of paper characteristics and how they relate to the specific print technology. Digital Presses use dry ink, which is a very fine powder. Litho presses use liquid ink. The following stock properties interact with the dry ink to determine the quality of colour images. At The Printing House (Print Buying Direct) we have 3 offset litho presses, all manufactured by Sakurai (ideal for high quality colour printing of annual reports, brochures, leaflets, flyers and newsletters. One large format inkjet (ideal for large posters, pull up banners etc) and a Xerox Digital Press (ideal for short run printing, business cards, appointment cards, postcards, posters etc).

BRIGHTNESS

Brightness is the measure of blue light at 457 nm. Brighter papers produce images with higher contrast.

Be aware that some artificial brighteners can affect colour reproduction by reflecting colors unevenly. A bright blue-white paper may reflect more blue and less red and green, affecting how the eye perceives the paper color.

Blue-white papers contain ultraviolet (UV) brighteners that break down over time when exposed to UV light. As UV brighteners break down, the paper shade may change from bright white to a warm white (yellow cast). UV light exists naturally indoors and outdoors.

RECOMMENDATIONS FOR BRIGHTNESS

As a general rule, use brighter papers when printing documents with photographs, halftone images, or complex graphics. Ideal for brochures, annual reports, postcards, leaflets and flyers.

FINISH/ SMOOTHNESS

Finish is the smoothness or roughness of a paper’s surface. Paper is processed to have a specific type of finish, ranging from very smooth to highly textured. Finish can significantly impact image quality on the printed sheet. If paper is too rough, light patches and graininess appear in solid areas. Halftone images also
appear grainy. Dry ink may not fuse properly to extremely rough paper, which may cause deletions where the ink rubs or flakes off. Wet ink suffers from muted colours and drying issues, always allow longer for uncoated papers to dry.

Smooth and coated papers produce sharp images because they reflect light more directly than
rougher papers.

Sheffield is a test that is used to measure the smoothness of paper. It measures the rate of air flow over the surface of a sheet. The lower the Sheffield smoothness number, the smoother the sheet.

RECOMMENDATIONS FOR FINISH/ SMOOTHNESS

Use smooth or coated papers for proper dry ink transfer to ensure the best colour density and image detail, and to increase the appearance of glossiness. Using a very smooth paper is especially important when printing fine lines and detailed images.

SHADE

Shade is the color of the paper. Paper shade may change the colors of printed images because ink is transparent and also is applied in dot patterns that allow the paper shade to show through. Lighter images reveal more of the paper color than darker images.

RECOMMENDATIONS FOR SHADE

• Select a true white for the truest colors and natural looking skin tones.
• Be aware that shaded paper will affect image colors and overall hues.
• Remember that paper shades can vary significantly among brands and lots.

FORMATION

Formation is the distribution of fibers and fillers in paper. Fibers and fillers should be distributed evenly throughout the sheet. Although formation is not included in the manufacturer’s specifications, you can check it by holding a sheet up to a light. If the sheet looks even throughout, it has good formation. If
you see uneven light and dark areas, formation is poor. Good formation is especially important when documents include halftone images of photographs or high ink coverage. Halftone images appear sharper
on paper with good formation. Solid images can appear uneven or spotty when printed on paper with poor formation.

RECOMMENDATIONS FOR FORMATION

• Choose paper with good formation to ensure uniformity of color images.

IMPURITIES
Impurities in the paper-making process can leave tiny specks in some stocks. The specks can appear as marks or spots in printed images, especially in high resolution images, fine type and fine lines.

Impurities in recycled papers consist of inks and adhesives (from window envelopes, stick-on notes, labels, etc.), which are difficult to remove during the recycling process.

RECOMMENDATIONS FOR IMPURITIES

Use high quality non- recycled papers when the best image quality is required.

OPACITY
Opacity impacts the ability of a printed image to show through from the opposite side of a sheet or from another sheet below it. To increase a paper’s opacity, filler may be added to increase thickness or be applied as a coating.

Opacity is measured according to how much light a sheet blocks and is expressed as a percentage between 0 and 100. Most papers fall within the 80% to 90% range. However, an opacity of 98% will prevent a printed image from showing through on the opposite side of the sheet (show through).

RECOMMENDATIONS FOR OPACITY

• Choose paper with high opacity when printing on both sides of the paper or when heavy dry ink coverage will be applied.

For More information of assistance please visit either of our websites – The Printing House Ltd – Print Buying Direct – or call us on UK number 0870 950 8444.