Ghosting in Heatset Web Offset Printing (Part II) - Zellcheming

Dr. Gerd Meder*, Mohn media, 

Carl-Bertelsmann-Str. 161 M, 

33311 Gütersloh, Germany 

Dr.-Ing. Wilhelm Busse, 

Verein ZELLCHEMING e.V., 

Emilstr. 21, 

64283 Darmstadt, Germany 

Dipl.-Ing. Maik Coesfeld, Mohn media, 

Carl-Bertelsmann-Str. 161 M, 

33311 Gütersloh, Germany 

The ghosting printing problem in 

heatset web offset printing is understood 

as the reduction of the tonal values of 

the printout on one side, caused by a 

motif or colour combination pattern on 

Das Papier Science and Technology 

Dr. Erich Frank, Flint Group Germany GmbH, 

Sieglestr. 25, 70469 Stuttgart, Germany 

Anne-Sopie Gombart, 

Sappi Netherlands Services B.V., 

Biesenweg 16, 

6211 AA Maasticht, Netherlands 

Dr. Joop van Hesteren, Solco NV, 

Zwaluwbeek14, 

9150 Kruibeke, Belgium 

Dr. Dirk Lawrenz, BASF Aktiengesellschaft, 

ED/PD – H 201, 67056 Ludwigshafen, Germany 

the reverse. This is clearly not just a case 

of the image on the reverse showing 

through or the penetration of oil or water 

from the ink on the reverse. 

Dr. rer.nat. Christian Naydowski, 

Voith Paper Holding GmbH & Co. KG, 

St. Pöltener Str. 43, 

89522 Heidenheim, Germany 

6/2008 

Peter Resch, Sappi Papier Holding GmbH, 

Brucker Str. 21, 8101 Gratkorn, Austria 

Dr. Joachim Schoelkopf, 

Omya Development AG, 

G. Meder, W. Busse, M. Coesfeld, E. Frank, A.-S. Gombart, 

J. van Hesteren, D. Lawrenz, C. Naydowski, P. Resch, and J. Schoelkopf 

P.O. Box 32, 4665 Oftringen, Switzerland 

*correspondence address: 

gerd.meder@bertelsmann.de 

Ghosting in Heatset Web Offset Printing (Part II) 

Reference 1 presented a model for the 

occurrence of ghosting. Ghosting was 

explained as interactions during the separation 

of the paper web from the rubber 

cylinder (Fig. 1) as a result of different 

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6/2008 Science and Technology Das Papier 

Das Papier · Summary 

Ghosting in Heatset Web Offset 

Printing 

The ghosting printing problem will 

be examined on the basis of test 

samples and a test form (sample 

printouts and rubber blankets). It 

tack forces on the front and reverse and 

the consequent continuous reduction in 

dot size. This reduction in dot size leads 

to a reduction in the tonal values and is 

the reason for lightening. 

Ghosting, which only occurs after a 

certain number of rollovers and which 

largely depends on the materials used 

– paper, ink, fountain solution, rubber 

blanket – is controlled by the tack forces 

and thus by the colour combination on 

the two sides. 

Das Papier 2008–T57 

will be shown that the study of the 

deposits on the rubber blankets and 

the comparison with the deposits 

typical of the offset technique bring 

about a greater understanding of the 

phenomenon. 

The influence of the colour combinations 

on the two sides (front and reverse 

of the printed page) on ghosting will be 

examined in greater detail here. First 

let us look at a number of examples of 

ghosting in practice. 

Fig. 2 displays a print sample in which 

only the colour black was printed on 

both sides. The contour and darker area 

around the number on the reverse side 

can be clearly seen. The darker area 

is the one that is not affected by the 

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number and ghosting is caused by the 

black reverse side around the number. 

Fig. 3 gives an example in which the 

red letter P on the reverse can be clearly 

seen as a bright image in the orange area 

(CMYK tonal values of the print plate 

specified in the image). Clearly the magenta 

on the reverse side has influenced 

the magenta on the front. 

Fig. 4 shows a grey area (CMYK, 30 % 

each) whose reverse produces strong 

ghosting (in the area of the hair) with 

equally high tonal values in all colours. 

Which colour on the reverse causes the 

ghosting? 

Fig. 5 presents a cyan yellow area on the 

ghosting side which is influenced by the 

colour combination on the reverse. The 

tonal values for all colours entered in 

the images show that ghosting occurs in 

points 1 and 3, in other words where the 

colour on the reverse is black.


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These real examples of ghosting provoke 

the question: which ink on the front 

(ghosting side) is actually influenced by 

which ink on the reverse? Obviously 

it cannot be assumed that the ghosting 

effect only occurs between two identical 

colours, i. e. within a single print unit 

(Fig. 1). 

We must assume that direct ghosting 

(within the same print unit) and indirect 

or consecutive ghosting (consecutive 

print units are affected) exist as shown 

in Fig. 6. 

Which combinations of colour on the 

front and back produce ghosting? 

The combinations for direct ghosting 

are blackblack, cyancyan, magentamagenta 

and yellowyellow. There are many 

more combinations for indirect ghosting. 

Fig. 7 demonstrates a number of 

combinations. The figures are intended 

to explain how an ink applied in a print 

unit (e. g. magenta in print unit 3) passes 

through the following print units by 

means of the paper web. 

When it comes to indirect ghosting, the 

question is whether a subsequent colour, 

e. g. the cyan on the reverse, can influence 

the black on the ghosting side (tack 

force difference FSC in Fig. 7) or is it 

rather the colour previously applied to 

the reverse side, black, that influences 

the subsequent ghosting colour, cyan 

(tack force difference FCS in Fig. 7). 

Is an influence only relevant over one 

colour interval (subsequent print unit 

only) or can magenta also be influenced 

by black and what happens when the 

colours are overprinted? 

To answer these questions, we shall consider 

the test form already used in 1 , 

Fig. 8, in which different colours were 

combined for the ghosting side and the 

reverse side. Fig. 9 exhibits the rubber 

blankets for the ghosting side belonging 

to the test print copy. 

The black rubber blanket presents the 

ghost effects in all colour combinations 

that contain black, while the cyan rubber 

blanket shows the ghosting effects in all 

colour combinations containing black 

and cyan. The magenta rubber blanket 


evidences ghosting effects for all colour 

combinations that contain black, cyan 

and magenta. 

Interestingly, all rubber blankets feature 

increased ghosting effects in the colour 

combinations that feature colours that 

precede their own colours. For example, 

in the case of the cyan rubber blanket, 

the CMYK and MYK colour combinations 

(K before C) feature greater ghosting 

than the colour combination CMY, 

even at much lower tonal values. 

In the case of the magenta rubber blanket 

(Fig. 10), the combinations K40C 

and K40M (M or C after K!) do not 

feature indirect ghosting, but C40K and 

M40K certainly do (K before M or C!). 

During indirect ghosting, the inks on the 

upper and lower rubber cylinders do not 

connect with the paper at the same time 

(as is the case with direct ghosting) but 

rather the already partially penetrated 

ink applied to the underside of the paper 

web comes in contact with the fresh 

ink of the upper rubber cylinder. At a 

printing speed of about 8 m/s, the previous 

ink (the emulsion) had about 0.1 

seconds to transfer oil and water to the 

paper. Thus, this dot will become tacky 

at an earlier stage or will remain tacky 

for longer if a larger amount of ink is 

applied, leading to increased tackiness. 

However, it is precisely these differences 

in tack that are the decisive reason for 

ghosting. 

To summarize: A subsequent colour (e. g. 

magenta) cannot influence the previous 

colour on the other side (e. g. black), 

but a previous colour (e.g. black) can 

influence the subsequent colour (e. g. 

magenta), Fig. 10. 

The degree of this printing error mainly 

depends on the type of ink and, in particular, 

on the ability of the paper to absorb 

water and oil. However the tendency 

remains basically unchanged. 

Fig. 11 presents the influence of twosidedness 

of paper. After the motif has 

been printed on side 1, the paper web 

was turned and printed on side 2. This 

example evinces that even if it was not 

possible to eliminate ghosting, a marked 

difference could be achieved. 

6/2008 

Is the printing error – the lightening on 

the ghosting side – caused by the colour 

combination and thus by the tack forces 

always the same or can a page even be 

darkened? 

To examine this issue in quantitative 

terms, the lab values (Fig. 12) were 

measured in the ghosting areas. Figs. 13 

and 14 present the L/L0values, (L0 

=L of 20 %) for different combinations 

of the upper and lower colour combination. 

Fig. 13 shows that ghosting only 

occurs with a ratio of tonal value tile / 

tonal value ghosting side = 2. In this example, 

direct ghosting only occurs in 

magenta. 

The upper images in Fig. 14 point out 

the influence of the preceding and subsequent 

colours. In the case of the paper 

type examined here, black on the tile side 

has the greatest influence on magenta, 

followed by magenta itself on magenta. 

The other combinations do not lead to 

lightening, i. e. ghosting, but rather cause 

darkening! 

Fig. 15 again clearly demonstrates that 

subsequent colours do not cause preceding 

colours to ghost, but also indicates 

that previous colours can have no effect 

if the subsequent colour is applied 

on both sides. The preceding colour 

has sealed the tile side like a film, thus 

creating different conditions for the subsequent 

tack. 

Once again, these curves are valid for the 

ink and paper used. If both are changed, 

the quantity of the resulting ghosting 

also changes, although the described 

working mechanisms remain valid. 

In order to further examine these working 

mechanisms, the input and output 

angle of the web was changed in the 

magenta print unit by installing deflector 

rollers, Fig. 16. In variant V1 the input 

and output of the web is unchanged, 

while in variant V2 the input of the paper 

web has been changed in such a way 

that the paper web runs symmetrically. 

In contrast, in variants V3 and V4 the 

output web was diverted either to run out 

symmetrically (V3) or to be compulsorily 

guided on the lower cylinder (V4). 

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Both in direct magentamagenta ghosting 

and in indirect magentablack ghosting 

the curves in Fig. 16 show that, 

because of the compulsory guidance of 

the output web, the separation of the 

web from the upper cylinder is no longer 

controlled by changing tack forces – the 

ink transfer and thus the tonal values of 

the ghosting side remain constant over 

the entire tonal value range. 

With direct ghosting, the paper web is 

separated and the ink transfer is disrupted 

in V1 and V2 with a tonal value 

ratio of (80/40=)2. With indirect ghosting 

the error occurs even with a lower 

tonal value ratio because of the penetration 

of the black ink in the paper and the 

consequent increase in tack. 

Let’s take a closer look at the dots of the 

three colour combinations marked in 

Fig. 8 for the four variants. 

Fig. 17, colour combination M20M50, 

shows the already familiar pattern whereby 

dot M20 within the tile area (M50) is 

smaller than the dot outside. In Figs. 18 

and 19 these dots were compared with 

those of variants V2, V3, V4. In the case 

of variant 2, the dots inside and outside 

the tile are largest and are almost the 

same size. Because the paper web feed is 

symmetrical, the penetration pattern on 


both sides is the same and the tack ratio 

does not change. In the case of variants 

3 and 4, the dots are also of the same 

size, but much smaller than is the case 

with V1, V2. The transferred dots have 

extremely sharp edges thanks to the 

compulsory guidance of the paper web. 

In relation to the deposits in the ghosting 

area, the sharp separation means that 

the penetration of oil and water into the 

paper is minimal, the deposits on the 

rubber blanket increase and narrow the 

dot. 

In V3 and V4, a slower buildup is expected 

because of the long contact time 

and thus dots form that are less sharpedged. 

It is clear that V1 has the dots 

with the sharpest edges and V2 the dots 

with the darker core. 

Figs. 20-22 display the behaviour pattern 

of the dots for the colour combination 

M40K50. With this indirect ghosting, 

the dots in V1 and V2 inside the tile 

area are much smaller than those outside 

the tile. The black ink (Fig. 22) has 

already penetrated and can build up a 

marked difference in tack from magenta 

in the magenta print unit. The compulsory 

guidance of the web at the outlet 

in V3, but in particular in V4, prevents 

ghosting here. 

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Finally, let us consider Figs. 23-25, the 

colour combination K20K70. The paper 

input and output were only varied in 

the magenta print unit and the black 

print unit is completely unchanged. All 

variants feature almost no difference in 

the dot values; variant 2 features a less 

precise printout, while variant 4 has the 

printout with the sharpest edges. 

If, following these explanations, we look 

back at Figs. 26, it becomes clear that 

ghosting samples 1 and 2 are clearly direct 

ghosting, namely blackblack (Fig. 2) 

or magentamagenta (Fig. 3). In ghosting 

example 3, the measurement of the lab 

value indicates that the grey tone has 

moved into the red and indirect ghosting 

exists through black and cyan. Finally, 

ghosting example 4 also shows indirect 

ghosting – black influences the cyan on 

the ghosting side. 

References 

1 Meder, G.; Busse, W.; Coesfeld, M.; 

Frank, E.; Gombart, A.; van Hesteren, 

J.; Lawrenz, D.; Naydowski, C.; Resch, 

P.; Schölkopf, J.: Ghosting im Rollenoffsetdruck. 

FograTagung München, 

November 2007, Druckfarbe und 

Papier


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Ghosting in Heatset Web Offset Printing (Part II) - Zellcheming

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