Print Density Control

Problem:	Printed Sheets show color variation from sheet to sheet during the run. Ink film densities are very unstable.
Causes:	Low ink level in the fountain Improper roller setting Ink Emulsification Ink backing away from the "fountain" roller Roller Stripping Contaminated ink fountain – dust, grit, etc.
Solutions:	Keep ink fountain full to maintain head pressure Reset rollers Decrease water or add heavy body varnish Agitate ink in the fountain or increase ink flow Deglaze the rollers Remove ink, clean fountain, replace with fresh ink

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The aim of the Tele Colour Matching (TCM) system is to provide fast and accurate matches of any ‘non process colour’. With TCM the influence of the substrate on which will be printed is taken into account when formulating the recipe of the colour to be matched and mixed.

Procedure

The customer spectrally measures the reference colour from a colour guide, an earlier print or a colour sample. Also he spectrally measures the paper on which will be printed. Especially the latter is essential in order to increase the accuracy.

The above measurements are E-mailed to Ink and Print together with information about the paper quality on which will be printed (coated or uncoated) and the quantity needed.

Based on the data received Ink and Print manufactures a colour by means of the Gretag Ink Formulation software which is regularly updated in order to guarantee a highest possible accuracy.

After the colour is manufactured Ink and Print makes a check on a slip of paper to carry out an extra check. This slip of paper will not be sent to the customer because this is not the substrate on which finally will be printed. With the delivery a form will be enclosed with the measurements sent by the customer and the measurements checked by Ink and Print. Furthermore the reference number of the recipe will be mentioned on basis of which the colour is mixed.

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Specification of lightfastness figures in accordance with the international standard C.E.I./02-59.

Lightfastness value:	8 = exceptional	4 = fair
	7 = excellent	3 = moderate
	6 = very good	2 = poor
	5 = good	1 = very poor

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One of the most difficult types of printing jobs in sheetfed offset is printing non-absorbing materials with conventionally drying inks (i.e. without any application of forced drying). However using the right materials and following the right procedure will enable the printer to obtain perfect results in both quality and efficiency.

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