When viewing a printed sample it is often difficult to tell which process has been used simply by looking at it with the naked eye. However, if a printed sample of the text area is examined with the use of a magnifying glass, the following characteristics are visible.
• Clean edges around Lithographic print
• Outline edges around Flexographic/Letterpress print
• Dotted edges around Gravure print
• Coarse/dotted edges or clean edges around Screen print, depending on screen mesh used
It is undoubtedly a considerable asset to be able to determine with reasonable accuracy the printing process or processes by which an item of printed matter has been produced. There are a number of characteristics or clues which, if they can be discerned, make identification of the process possible, but not necessarily simple. Indeed, there are some jobs where it is very difficult to identify the relevant process or processes, even to those having considerable experience, and the use of a powerful magnifying glass or ‘linen tester’ is of considerable value.
Offset Printing
• Overall, smooth and even printed result
• Very wide range of substrates including coarse textures, can be satisfactorily printed, even when very fine halftone illustrations are reproduced
• Tonal effects obtained by the use of mechanical tints or halftones.
Flexography Printing
• Thickening of design under pressure, along with a general outline to the printed areas in the form of a visible halo, especially around the outer edges
• Tonal effects obtained by the use of mechanical tints or halftones
• Fine‐screen halftones must have substrate with a coated surface
• Printed samples often obtained from processed material in reel‐form such as self‐ adhesive labels, plastic and paper wrappings.
Letterpress Printing
• Thickening of design under pressure, along with a general outline to the printed areas in the form of a visible halo, especially around the outer edges.
• Slight embossed effect usually detectable on reverse of sheet, especially with sheetfed printing.
• Tonal effects obtained by the use of mechanical tints or halftone dot
• Fine‐screen halftones must have substrate with a coated surface.
Gravure Printing
• Wide range of tonal values is possible, giving an effect of continuous tone‐like quality (especially in four‐colour process work)
• Because of the screen pattern or cell structure, which appears over the whole of the printed image, fine‐line work and text matter appear rough/broken at the edges when examined with a magnifying glass
• Under a magnifying glass the ‘screen pattern’ in conventional gravure is seen to be of a regular square formation (showing uniform cells).
Screen Printing
• Thickness of ink film is usually more apparent than in other processes, especially where solid colours are printed upon one another.
• Because of the use of relatively coarse screen meshes, forming the support for the stencil, small lettering and fine‐line work tends to break up round the edges and this can be identified when examined with a magnifying glass.
Digital Printing
• Overall, smooth and even printed result.
• Fine‐screen halftones must have substrate with a coated surface.
• Printed samples often obtained from processed material in reel‐form such as self‐ adhesive labels, plastic and paper wrappings.