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Manufacturing Guidelines

There are certain variables that can affect components during production and though on their own they can be small, they can combine to affect the final cover design on the trimmed book. By following the advice detailed below you can remove any potential problems pre-printing.

Maximum ink coverage

When designing work using 100% of all 4 process colours, there are potential problems due to curing of the black ink. If a black solid is covered by another 3 solids, the curing of the ink, and consequently the keying to the board, can be affected.

Ink that is not dry can be transferred to the for-edge of the books when trimmed in the bindery. Ink that is not cured can flake off the board, including any finishes on top, i.e. foil and varnish. With large areas, the adhesion of the laminate can also be affected, and UV varnish can give a mottled effect. Maximum ink coverage should not therefore exceed 350%.

Ink takes longer to dry on uncoated board (including the reverse side of coated stock), so for these designs, the ink coverage should be limited to 240% in total. Again, this will minimise any chance of drying issues or marking.

Printing on Wibalin cloth

Because the ink has a tendency to rub off after printing on Wibalin, we will always apply a seal varnish after printing to seal the ink. This will incur an additional cost.
Clothbound Book

Metallic colours on solid printed endpapers

It is strongly recommended that metallic colours are avoided on solid printed endpapers, there is a high risk that ink will rub off onto the inside flap of the jacket.

Uncoated cover board

Uncoated cover board such as Colorplan or Astropack is frequently used but does carry some higher risks in production. It is particularly susceptible to the transfer of ink onto the cover during the manufacturing process and dirt beyond. Specific cover designs are more at risk of this than others, especially if there are areas of low ink coverage or a high degree of contrasting areas of colour. Please speak to your account control to gain further advice on how best to maximise the chance of producing an optimum product using these materials.
In addition, the following requirements should be followed:

Ink coverage: Ink takes longer to dry on uncoated board (including the reverse side of coated stock), so for these designs, the ink coverage should be limited to 230% in total. This will minimise drying issues or marking.

Foiling: When foiling on unfinished cover board/jacket paper we need to use the HC foil grade. This foil is thicker than our standard foil which enables us to apply additional heat and pressure to ensure the foil reaches the bottom of the grain and transfers successfully.

Spot UV: We would not recommend applying spot UV onto unfinished cover/jacket paper as because of the absorbency of these substrates, the finish of the spot UV is often quite dull and patchy. This finish will therefore be at the customer’s risk.

To achieve a consistent result, an alternative is to use a clear foil (Kurz ref V949). To enable the foil to key to the cover/jacket, we also need to seal varnish first.

Holographic foil

Holographic foil is actually manufactured in sheets and then joined together into a roll before the foiling process. Where these join you’ll see a “band” of a slightly different colour. Although we have worked with our suppliers to minimise this it cannot be totally avoided.

Printing over foil - Design recommendations

  • Avoid areas with a tight fit between blocking and printing.
  • Avoid small areas of foiling and over-printing as there is an indentation made on the sheet at foiling stage which is then difficult to over-print.
  • Sheet distortion takes place in both processes so fit can vary between foiling and over-printing. This is more noticeable on the back edge of the sheet.
  • Always laminate job to ensure ink doesn’t scratch off foil.

Hard “scuff free” matt lamination

To minimise scratching and scuffing of laminates, particularly noticeable on designs with a dark background, hard matt lamination is recommended. Hard matt lamination is more expensive than standard matt or gloss; please contact your account controller if you require a price.

Pile, glitter textured and matt spot varnish

Pile spot varnish is a deeper layer of varnish and is often used as an alternative to embossing or where the inside cover printing should not have the image distorted by embossing, i.e. over an author’s picture.

Glitter spot varnish is increasingly popular and although other colours are available on request, we currently stock gold, silver and crystalina. Two particle sizes are used, 004 and 008 and can be used on their own or mixed. Further information is available on request.

Glitter spot varnish is increasingly popular and although other colours are available on request, we currently stock gold, silver and crystalina. Two particle sizes are used, 004 and 008 and can be used on their own or mixed. Further information is available on request.

For all of these finishes, the following guidelines should be followed:

  • These types of varnish should not be positioned over folded, creased or trimmed areas.
  • Another varnish (i.e. glitter) cannot be applied over the top of the varnish. It cannot be embossed as it will crack and “flake off”.
  • Glitter varnish with large solid areas of cover will take longer to produce and so could require a longer schedule.
  • As with normal spot varnish, glitter spot varnish will soak into an uncoated board such as Colorplan and the “glitter” will then flake off. The way around this is to clear foil the areas first, and then glitter varnish over the top.


Clays standard embossing route to achieve the maximum appearance of depth, has a “domed” shape to the embossing. Other effects can be achieved such as chiselled, textured or layered embossing so please speak to your account controller for more details.
Embossed paper

Card tip-in at front, back or both of book, with inside cover printing

For this design, the following guidelines should be followed

  • The image must bleed 2mm into spine on inside front OR inside back cover. This should help to avoid white line between cover and tip.
  • 2pp card tip: no finish (i.e. varnish) to appear within 3mm unsewn allowance and 3mm in trimmed back (i.e. 6mm unfinished strip in total) to facilitate binding. 
  • Cover finish on inside printing: no finish (i.e. varnish) to appear within 3mm of spine on inside front cover or inside back cover as applicable to facilitate binding.


Supply specification:

It is important that stickers feed off the reel feet first in order to avoid hand stickering.

General requirements:

  • label spacing should be a minimum of 2mm
  • reel width should be 290mm
    • we can accept reel width of less than 290mm but please make as wide as possible
  • reel core is 44mm
  • label width is 6-55mm
  • label depth is 12-40mm
  • there is a 1mm tolerance when placing stickers
  • stickers per reel
    • please supply as many stickers per reel as possible, for example, if there are 6000 stickers supply as 1 reel of 6000 stickers rather than 2 reels of 3000 stickers


Round and Backed / Flat backed

The minimum text bulk for round and backed is 10mm, below this the book will be flat back (with a board hollow).

Covers with Flaps

The production method for this style of binding entails two runs through the binding line. Due to this process, we achieve a much cleaner and stronger final binding result if we side glue the covers.

Webroom – Text printing

Halftone printing on text paper

Halftones can be successfully printed on text paper, however a number of factors need to be taken into account when supplying data, if the optimum printed result is to be achieved.

At Clays we use cold set web presses, where, typically, mechanical dot gain on the printing press will be in the region of 22% (industry standard). To avoid the shadow (dark) areas of your illustrations printing unacceptably dark, the maximum dot size on your data should be no greater than 80%, conversely the highlight (light) areas should be no less than 7%.

Any dot size greater than 70% may result in a dark image lacking in detail and contrast.

Choice of paper plays a major role in determining the quality of the printed result. A significant contributor to dot gain is the dust on the surface of the paper, which allows the ink to spread or the dot shape to change. A good quality dust free paper will provide a far superior result compared to a dusty paper. If you need help with choosing an appropriate paper, please contact your account controller.

Wherever possible, halftones should be avoided in the first or last sections of the book (1st 32pp or last 32pp) as a certain amount of “set-off” (i.e. ink transferring onto the page facing the halftone) is inevitable due to the binding process. This will be particularly noticeable on hardback titles, if the illustration or tint is particularly dark or if the illustration is facing the title page or a blank page.

If you have a title where positioning of halftones on these pages is unavoidable, please contact your account controller to discuss. 

If the subject is a series of tint blocks (a bar chart for example), the tints should be a minimum of 7% going up in steps of no less than 10% (to ensure definition) to a maximum of 70%.

Halftone images should be supplied without a screen ruling. Clays will apply the screen ruling of 150 lines per inch for illustrations printed on text paper and 175 lines per inch for illustrations printed on separate, coated paper.

Creating a “stencilled” image on edge through bleeding fore-edge printing

Our guidelines are a minimum of a 6mm ‘tab’ image on the fore-edge – 3mm inside and 3mm outside of the trim.