Spine Widths for Covers

NB Please contact your account controller if your job has an extent over 1000 pages and is being printed on thin paper, as you may need to add extra into the spine.

Text Bulk

Text Bulk (TB) is the thickness of all the pages together, which determines the spine width. The bulk of the text paper in the book is calculated as follows:

The extent (in pages) multiplied by the thickness of the paper (in microns) is divided by 2000. This gives the bulk of the text in mm.
e.g. an extent of 224 pages on paper of 110 microns: (224 x 110) / 2000 = 12.32mm = TB

Text Bulk Adjustment

For TB calculated up to and including 10mm, add 0.5mm. This becomes the final calculated bulk. For TB calculated over 10mm, round the figure up or down to the nearest whole mm
e.g. 12.32mm becomes 12mm; 15.6mm becomes 16mm

Unsewn Paperbacks

For text bulks over 10mm, up to and including 45mm, add 1mm
e.g. TB = 30.7mm, final bulk = 32mm

For text bulks over 45mm, add 2mm
e.g. TB = 47.1mm, final bulk = 49mm

Sewn paperbacks

For text bulks over 10mm, up to and including 25mm, add 1mm
e.g. TB = 23.8mm, final bulk = 25mm

For text bulks over 25mm, up to and including 35mm, add 2mm
e.g. TB = 32.3mm, final bulk = 34mm

For text bulks over 35mm, up to and including 55mm, add 3mm
e.g. TB = 45.5mm, final bulk = 48mm

For text bulks over 55mm, add 3.5mm
e.g. TB = 60.7mm, final bulk = 64.5mm

Spine Widths for Cases & Jackets
Rounded and backed books

Notes:

• for intermediate bulks add the increase used for the next listed bulk.
  
• please contact us about spine widths for books bulking over 56mm.
  
• final bulk will always be subject to variation in paper micron.

Flat backed books

Text Bulk + (Board Caliper x 2) + 1
e.g. a bulk of 36mm with 2250 micron boards would be: 36 + (2.25 x 2) + 1 = 41.5mm