The published articles are meant to primarily educate the students in printing to supplement their knowledge in the field of Printing. These are not simple Glossary of printing terms, but to the extent possible every term has been explained in brief so that it can be of some use to the students who appear in some sort of examinations and interviews.
I served the Printing Industry for over 40 years
in various capacities, a major part in an Security Printing Organization. In order not to waste the printing and paper related knowledge which I gained over years, I decided to keep them in public domain for the reason stated in prepara. Most of the illustrations - over 90% - have been generated by me to explain the terms suitably.
While I am not sure to what extent the published content will help, if the content is going to be of use to some one in some manner, I will be greatly satisfied.
Your views may be sent to me (
nrj_1945@yahoo.com) for my record and correction wherever needed.

TOTAL NO OF PRINTING TERMS

POSTED TILL NOVEMBER, 2012

- Over 400 terms-

Click on this line to read from 'A'

Saturday, June 25, 2016

Fluff/ Debris and Hickeys- Clarification


  (Written by N.R. Jayaraman)

Questions and Clarifications


With reference to my clarifications published vide Part-1 to Part-IV on the subject ‘Printing defects on the Canadian Currencies and Coupons’ which were in response to the original articles of Mr Hitesh Doshi  (Ref:-Doshi.H. / Email: Hitesh Doshi -hdoshi@ryerson.ca), he has raised few more important queries and sought elucidation on the subject further. They are reproduced below in the form of ‘Question and Clarifications’ for the benefit of readers:

Question:-

Sr No 1:- 
Quote:- With respect to fluff and debris there is often a term that I have seen used called a hickey? Many textbooks have provided an explanation of how hickeys happen. You do not seem to have used that term and I was wondering the reason for that. - :Unquote

Clarification:-

Let there be no confusion on Fluff and Debris on one side and Hickies on the other. Both are different terms meant to express two different types of problems and vary in behavior. While Fluff/ debris cause void spots in the print, the hickies may or may not cause white spots. Either there will be a hazy, non sharp, uneven white ring around the hickey spot or there may be a dab like appearance in the midst of the print. This is the reason why the term hickies have not been used along with the term Fluff/ debris in my article as they were basically two different problems. Quite often people may get confused with the prints which have hickey problem, and appear with void rings as though they are fluff.

Question:-

Sr. No -2
Quote:- Also I have another article that is coming up (I will share that with you as soon as it is published) which discusses the differences when the debris is stuck to the plate or the blanket. I am wondering if you believe it makes any difference    :Unquote

Clarification:-

The following narration will clear the doubt on the behavior of Fluff/ debris and that of Hickeys when they stick to the plate or the blanket surface.

a) The problem of Fluff or debris occurring on the Dry Offset printing process is not related to the Ink but related only to the paper surface and the blanket. The problem of Fluff/Debris will also not occur either in the Letterpress or in the Intaglio process of printing as the paper on which the print is made is in direct contact with the plate and not through the blanket.

b) The extraneous particle called Fluff/ debris emanating from the surface of the paper stick to the surface of the Offset printing blanket during printing process. Once the particle is stuck on the blanket, from then on they resist the transfer of the image from the plate over their surface (over the particle), resulting in the print to appear with voids or no image spots in those areas where they are stuck. This is because they are shiny and non absorbent material and may have been converted to such nature during bleaching and calendaring process in the paper mill which polishes their surface, and when they embed on to the surface of the paper as dried particles, their surface remains polished and therefore reject the inked image. The fact is that the  ink slips away from the surface of the particles stuck on the blanket. 



c) The Fluff/ debris is directly related to blanket vis-a- vis Paper surface. Till the particle stuck to the blanket is removed, the void will continue to appear on subsequent sheets that follow the first sheet affected with fluff. The appearance of voids on the print will also be uniform in size and shape on all prints alike the embedded foreign particle sitting on the blanket surface. 

d) Only in Letterpress and Intaglio printing the paper has direct contact with the plate. In letterpress printing process only the coated stocks and inferior quality paper made from low quality wood and other mechanical pulp transfer the fluff/ debris from their surface on to the plate/blocks which in turn pass on them to the inking rollers in contact with them. Thus the ink gets contaminated with the accumulation of the paper dust and debris and when they continue to ink the plate it results in the reproduction of unsharp, hazy image on paper but will not show any voids on print.

e) Now take the case of Hickies. When extraneous particle stick to the surface of the plate, they interfere in the plate receiving proper inking  over the image for further transfer to the paper. Be sure 95% of the particles may have been from the ink rollers which may have received the hardened particle like dried ink or other dried particles from the ink duct. During the inking process some of those particles travelling in the inking rollers get released from their surface and stick to the surface of the plate. Do not expect the extraneous particle over the Plate to behave like the extraneous particle on the blanket. Either the plate will hold it for some time or instantly transfer it back to the inking rollers or transfer it on to the blanket or on to the paper directly depending upon the process deployed for printing. The resultant image on the print will be a blotch on the printed image with a hazy void ring around them which will also be not uniform in size and shape and vary from print to print. 



f) Some times the extraneous particle thus stuck on the surface of the plate will remain there firmly. During the inking process, while the image areas receive normal inking, the spot where the extraneous particle is stuck on the plate will also receive the ink but particle being slightly raised from image level, the outer portions of the particle will not receive the ink properly. This is the reason why when the image gets transferred on to the surface of the paper, the print will appear with a blotch of ink surrounded by a ring of void in those areas where the foreign particle is stuck on the plate. Such a particles are called Hickies. In this process few sheets printed without removing the Hickey will show the blotch mark but the important point to be noted here is that the appearance of the blotch surrounded by a ring of void may not be uniform since in the continuous inking process, some quantity of the ink may also intrude into the sides of the foreign particle on the plate and reduce the effect of void.  The effect will thus be fluctuating. 

g) Sometimes the top layer of the ink in the duct gets dried and form a thin layer of dried film. If the operator failed to remove them they too would get mixed with the ink in the ink duct and transfer them on to the inking rollers. During inking process, such hardened particles which had traveled along with ink stick to the surface of the plate. Such hardened or contaminated ink particles cause the problem of hickies in Letterpress printing process or even in the wet Offset printing process. Both result in the reproduction of the same effect – a blotch surrounded by void rings on print in the areas where the dried ink film particles were stuck on the plate. However such occurrences are very low in Offset compared to the Letterpress printing.

h) The blotch of ink being wet, the blanket in wet Offset printing process picks it up and either hold it for a while or transfer it on to the paper surface. However in this process only few sheets will be affected before the operator notices them to stop the machine and remove the hickey.

i) If it is letterpress printing process, the ink blotch on the plate will transfer it on to the paper and the next one or few sheet will show unsharp image on the same spot, but the subsequent sheets will begin to take normal print.

j) Till the particle stuck to the plate/ blanket surface is removed, the subsequent sheets that follow the first sheet affected with the hickies problem will show some kind of a patch image on the print whose appearance will also be not uniform in size and shape on all prints. 



k) Sometimes the high viscose ink may pull out the paper coating or paper fibers when the plate transfer the image on to the paper surface. The pulling out of the fiber will show irregular shaped voids in print as the internal bond of the paper comes out unable to withstand the tack of the ink. At first sight the void appearance on  print will appear as though it was Fluff problem. Actually it is not and may have been the cause of high viscose ink. This is also a kind of an hickey only. 

l) The problem of Hickies occurs both in wet Offset and Letter Press printing process and rarely in Dry Offset and Intaglio printing. But again they do not result in printing of halo or void images. They will result in a dab like appearance encircled by a pattern like ring of irregular shaped void.

m) In Intaglio printing the problem of Hickies normally do not surface and  are very rare because after the plate receive the ink the surface is automatically wiped out to remove the excess ink by a unit fitted with Teflon blades. Therefore any blotch of ink stuck to the plate will be removed before printing. Beyond this, even if some ink spill falls from the duct on to the blanket of the impression cylinder, the back side of the paper will only be affected which can also be called unusual hickey. Therefore any extraneous particles like dried ink film or other hardened material sticking to the surface of the plate or the impression blanket cylinder in the Intaglio process will not cause voids/ ink blotch problem on the print. Only broken image problem or spreading of ink on the print showing unsharp image occurs in Intaglio. 



n) The problem of Hickies is directly related to the ink. Since the plate is in direct contact with the paper, during the process of printing the dust and other extraneous particles over the surface of the paper may also get adhered to the surface of the plate. The plate is in direct contact with the inking rollers to receive the ink. The inking rollers are in direct contact with the Ink duct. Now the paper dust once transferred on to the paper will also move to the inking roller and from the inking rollers they travel to the ink duct too and affect the ink in the fountain. The more and more dust thus getting transferred from the paper to the plate to the inking roller and to the ink in the ink duct like a chain will contaminate the ink in the ink fountain. Such of those dust when mix  with the ink converts some quantity of the ink into hardened lump like formation here and there. This happens when the machine is stopped for some time for any purpose. When such hardened particles travels back through the inking rollers and adhere on to the plate surface, they too cause problem like hickey.

o) In short the Hickey is the result of the following:
  • Poorly ground ink
  • High tacky ink
  • Top layer of the Ink partially dried in duct and continue to transfer ink with a thin film of dried ink
  • Paper dust getting mixed up in the ink duct to convert it to high tack ink
  • Too much dust in the atmospheric condition
p) One may ask, when the fluff or debris adhered to the blanket surface  resist the transfer of the inked image from the plate to cause void in print, how come the dried ink particle stuck on the plate can accept ink.

q) As I mentioned earlier the reason for the Fluff/ Debris stuck on the surface of the blanket refusing to accept ink  because they may have become non absorbent during bleaching and calendaring process which polishes its surface in paper manufacturing. The surface of the particle turns into glazed surface and therefore the ink slips away from sticking on them.

r) However any other dust or other particles like dried ink film if get stuck to the plate, they will receive the ink from the inking rollers as the particles mostly belong to that of ink and fibers from paper which are not only non absorbent in nature abut are also in semi wet condition.

s) In short the fluff and debris stuck to the blanket surface in Dry Offset printing process will result in halo or void to appear in print. Their appearance, shape and size will be uniform in all sheets; however the print on the paper with hickey spot will show imperfect image with or without halo whose size, shape and appearance will also be not uniform.

t) This is the huge difference between the behavior of Fluff/debris and Hickey stuck on the surface of the blanket and plate.

Question:-

Sr. No -3 
Quote:- Also I have read that in addition to the static related material such debris can also be contributed from particles of dried ink etc. This type of material cannot be removed by the static removal device that you mentioned but I have read that there are other ways that the presses automatically clean to remove hickey causing material without stopping the presses -: Unquote

Clarification:-

a) The Hickeys resultant problem on account of ink cannot be removed by the anti static rods like the one fitted on Offset machines to eliminate the static from the surface of the paper after which only the print gets transferred on to the paper surface. Static electricity occurs only on dry surfaces which are not wet. The Hickies are semi wet material partly stuck on the plate or blanket and therefore the anti static rods have no role to play to remove them from there.

b) The anti static rod cum dedusting unit is an ancillary equipment fitted on the machine that works in sync with the machine to remove the floating extraneous material from the surface of the paper and not those partially embedded particles from the surface of the paper or from the surface of the plate or blanket cylinder. 




c) There are few equipment and units available to remove the fluff/ debris  from the paper surface and the hickeys from the plate or blanket surface, both equipments, both of them attachable to the machine for online cleaning .

The normal process of removing Fluff/ Debris and Hickies are:

(i) In order to remove the fluff/ debris, one has to  stop the machine, clean the blanket surface manually with some cleaning solvents and restart the machine. Similarly to clean the Hickeys the same procedure is adapted. 



(ii) However to remove fluff/ debris or Hickies on machines fitted with online cleaning attachments, the machine is not stopped but the impression and feeder unit is disengaged. The washer/ cleaner unit is immediately engaged to clean the surface of the blanket or hickeys remover that wipes away the hickeys while the machine is still running and then the impression unit is re engaged again to continue the printing. These processes depend on the type of unit attached.

Question:-

Sr; No -4 :- 
Quote:- With respect to the broken image I have a question. Lets say the plate is damaged from the beginning. How many imprints would you expect from one damaged offset plate before the plate would be routinely replaced? In other words how many sheets can a plate be expected to print before it is replaced. The reason this is important is because the question arises whether an individual plate is damaged or whether the master has been damaged. The reason why this question arises is because the number of sheets that have been affected are in the order of more than a million sheets. - Unquote   


Clarification:- 

I am totally surprised how the Canadian Currencies with such glaring mistakes are issued in millions without getting them weeded out during inspection process? Is it the policy of the Central bank that Currencies and security Coupons with such mistakes are acceptable as long as the security feature are not affected ? Always certain parameters are defined for the acceptance of defects on the printed Currencies and accordingly the tolerance limits are set with +/- variations for inspection and acceptance, but not to this extent as seen in the samples analyzed by you. However if such instances occur by mistake of the inspectors that is a different story.


In India and many other countries I have seen such defective notes are not issued from the press and even by mistake if such have been issued they are tracked in banks and removed without further issuing them. Are the Canadian notes with such major defects issued in big lots? I still doubt.

a) Generally well processed plates can print not less than 10 million sheets plus in which each sheet will have the same image in multiple ups in the order of 20 to even 40 notes per sheet depending upon the size of the Currency and the size of the sheet used for printing them. That means more than one million pieces of notes per normal shift working in a day is easily achievable per machine. We have experienced even more.

In light of the above simple arithmetic no printer will continue the printing with damaged image (minimum one damaged note per sheet) unless it is emergency to produce few million currencies for issue urgently. Simultaneously damage free image plates will be made ready and replaced as quickly as possible. Especially the Currency printers will not continue the printing with plate that has damaged image once the defect is noticed. Printing the image with broken design will not be acceptable by banks and therefore replacement of them in the bundles after processing will only add up the cost on account of loss of paper, loss of ink, consumables, labor involved in printing and sorting.

b) If the master is damaged it will be immediately got rectified before further plates are processed. No plates are prepared for printing from the defective master.

Wednesday, June 15, 2016

Printing defects on Canadian Currencies : Part - 4



Brief summary

This is in continuation with my earlier article written in the same subject under the title Analysis on 'Printing defects on Canadian Currencies'. All those articles were based on articles written by Mr. Hitesh Doshi who teaches in the Architectural Science Department at Ryerson University, Canada 
(Ref:-Doshi.H. / Email: Hitesh Doshi -hdoshi@ryerson.ca).

The present analysis Case Study:4 is also on 'Printing defects on Canadian Currencies' and based on another article written by Mr. Hitesh Doshi titled  'Truncated issue on $20 frontier series polymer Canadian Bank Note' (Ref: Truncated issue on $20 frontier series polymer Canadian bank note Canadian Paper Money Society Journal 2015 ).

Mr. Hitesh Doshi has analyzed the possible causes of the defects seen in Image-1 and Image-2 as shown below and therefore it is necessary that the origin and actual technical problem is fully understood in all aspects. One of the most common technical problem faced by printers is occurrence of white spots called fluff or lint or debris as differently coined by the printers, that show voids or no print spots on the images in the ultimate print at the end of Offset printing process.

Four probable conditions have been mentioned in the article published. The probable conditions mentioned are:

Quote
1. Condition happened post-production
2. Condition happened during production but after printing of all ink
3. Condition happened during production but after printing of the 'Issue' text
4. Condition happened during production where portion of the 'Issue' text was never printed
Unquote


Yes, the cause of the truncated image is attributable to probable cause mentioned under Sr No 4 mentioned above. The portion of the text 'issue' has been printed as broken image. 


Analysis 

Both paper and Polymer substances are used for printing the Currencies and both have the tendency of fluffing and linting. This is unavoidable. Let us discuss the behavioral pattern of the paper used for printing the currencies and which are generally made from 100 % combed cotton having longer fibers. While some paper manufacturers add small percentage of recycled paper from the same mill to reduce the manufacturing cost, they are careful not to mix wood pulp or other mechanical pulps along with the cotton fibre pulp which will not only deteriorate the quality of print on the Currencies but also generate many working problems during printing. For reducing the manufacturing cost of paper, the suppliers quietly add the recycled paper pulp beyond the percentage permitted or add the ready bleached pulp cakes available in the market which are mixture of many other varieties of paper. With this combination when the paper is manufactured one will see endless problem of fluff and linting leading to the reproduction of prints with voids on the printed surface. No doubt, adding ready made pulp cakes help in reducing the manufacturing cost, but it also reduces the profit part of the printer due to the technical problems faced working with paper or other substances  prone to fluffing.

In addition to the short length of fibers inherited in the ready made pulp cakes, in whatever manner the readily available pulp cakes are treated in the beating process and filtered during the process of paper making, some amount of extraneous particles like fine chips of wood, crystallized gelatine, albumen flakes etc pass through the filters and mix with the final pulp that flows over the paper mesh to form the paper in the paper making process. Except the bigger particle, it is not possible to filter away the smaller sized extraneous particles. Loose material in the recycled paper or re-pulped paper may include threads, gelatine and plastic material, pollen etc and when they sit on the surface of the paper, they cause several technical problems during printing. Such floating extraneous dirt particles on the surface of the paper are the main culprit  that cause the problem of fluff and debris during printing.

Voids on the printed image 

How does the fluff and debris settle on paper and subsequently affect the print quality? During the paper making process when the pulp that forms the sheet of paper keep flowing on the mesh screen to form the paper, the extraneous dirt particles too flow along with the pulp and stay on the surface of the paper being formed and gets settled on it during drying process. During super calendaring process, they are all pressed on to the surface of the paper.Though the extraneous materials may appear to be firmly adhered with the surface of the paper, in reality it is not. While part of the floating material remain non bonded on surface of the paper due to static electricity generated during paper making process, some percentage of them partly remain fixed with the paper surface as if they have been pasted with gum. Till the static is removed from the surface, those floating elements will also not come out. Thus the paper that are prone to fluffing will have both floating and partially embedded extraneous material on them.

Once the paper making process is completed, those paper lot is packed and sent to the printers. Theoretically the static remains on the surface of the paper even after packing. Usually the static affected papers when subjected to printing refuse to release the dust and dirt particles from the surface unless some apparatus is engaged to remove the static from their surface during the printing process. 


If this problem of fluff or voids is to be eliminated during printing, the static on the paper surface need to be first taken out and extraneous particles removed. Sheet by sheet removal of static and the extraneous particles by wiping with semi dried damp cloth or some other means is not feasible as the quantity will be enormous. Therefore in order to eliminate the static on paper which cause the problem of fluff, a small unit called anti static cum dedusting unit is attached at the end of the feeder board, but before the impression unit. It is an attachment that has anti static rods and dedusting unit to suck away the loose particles. When the surface static is removed from the surface of the paper by the anti static rods, the dedusting unit sucks out the extraneous particles and other dust released from the static removed paper surface. However the partly stuck extraneous particles do not get loosened from the paper surface by the anti static unit and continue to remain there still. 
When the anti static and dedusting process failed to remove the partly adhered particles, they continue to remain adhered on the paper surface and reach the print station. When the paper pass through the blanket to receive the ink impression from its surface, the extraneous particles partly remaining on paper and not visible to the naked eye gets released under pressure between cylinders and gets stuck on to the blanket surface. Once the particle gets adhered to the blanket surface from then on the inked image from the plate refuses to transfer the image on those particles stuck with the blanket while the other portion of the images get normally transferred. When the inked image from the blanket gets transferred on to the paper surface the image will show voids on the print on those places where the extraneous particles on the blanket have not accepted the image transfer.

Printers call the voids as paper fluff which continues to print void images on the same position and in the same shape and appearance continuously on the entire set of sheets that continue to travel unless the machine is stopped and blanket cleaned to remove the dirt.

The peculiarity of those extraneous particles stuck on the blanket is that they do not accept the ink from the plate cylinder which transfers the image on to the blanket for re transfer on to the paper surface. Because the extraneous particles do not accept ink, the image is printed along with non inked areas which in technical term is called voids. Why the extraneous particles adhered on the surface of the blanket fails to accept the ink from the plate is that their surface becomes highly polished during super calendaring process and therefore the surface becomes  non absorbent due to which they repel the ink.

Similar to the paper substance which has the debris stuck to the surface during manufacturing process, the polymers too have their own family of extraneous material that gets stuck on their surface. The extraneous material partially or firmly stuck on Polymer substance when subjected to print process cause voids in the printed image as the loose particles get stuck to the surface of the blanket exactly in the same manner as it occurs during the print process on paper. Remember an important aspect on the image printed. The size, shape and appearance of the void is uniform on all the notes thus confirming the theory that the extraneous particle called fluff adhered over the blanket surface has been the possible reason for the said defect  even on the Polymer substance used for printing the currencies. This may be the cause for the defect as seen in the image shown under Image-1 above.

Note an important aspect; the void image is similar in all notes and of the same shape and size as seen in the Image-1 shown above.

Truncated image

The reasons for the second problem of broken or truncated image is explained below. 


While it is not known whether Wet Offset printing technique or Dry Offset printing  is deployed for printing the currencies in the Canadian security printing press, only general observation can be given for the causes.

The Currency note printers all over the world appears to generally use only relief imaged plates to print the Currencies and Dry Offset process which works in the simpler manner than the conventional Wet Offset machines that work on grease and water repellent theory.

Two reasons is attributable to the defect as seen in the above images under Image-2

Dry Offset print process:-

1) The image 'issue' on the relief Offset plate meant for the Dry Offset printing, may have got damaged in that particular portion by losing the relief depth if some hard object in the same shape and appearance as seen in the image may have pressed the image on the plate during impression. The extraneous object could be dried ink particles or particle from the cleaning cloth. The relief of the image on the plate may have gone down below the kiss touch point between the plate and the blanket cylinder.

2) If above have not happened, then it is possible that the blanket may have been damaged or punctured in that particular portion by  pressure of some extraneous particle to the extent where the image is truncated. Sometimes the blanket gets punctured by some hard particles.  The effect is non transfer of the image from the damaged area of the blanket causing truncated printed image.


3) Thirdly the problem of big sized fluff particle could have also been the cause that get stuck to the blanket and prevent further transfer of full image.

Wet Offset process:

Here too either the plate may have got damaged due to some scratch occurred  while handling the plate on the machine or hard particle has pressed the plate in that portion to the extent of truncated image or the blanket may have been damaged as pointed out under Dry Offset process.  

CONCLUSION 

==================== 
                                                           

In both the cases of printing by Dry Offset and Wet Offset process the result will be the reproduction of the truncated print as it appears on the Image-2 above if the plate had lost the image depth, or blanket was punctured or the extraneous particle like fluff stuck to the blanket surface preventing ink transfer from that particular portion truncated. Note an important aspect; the truncated image is similar and of the same shape and size as seen in the Image-2 shown above.

If the inspection machine failed to detect it, then defective Currency will go out for circulation as is the present case. The defect is very glaring and it surprises how it has passed for circulation.

Since various aspects involved in the issue of voids in print and truncated images have been explained in detail, the observations expressed  in the original article have not been taken up for analysis.

Wednesday, June 8, 2016

Comment- Part-3 a



In response to my article under Printing defects on Canadian Currencies Part-3, Mr Hitesh Doshi who teaches in the Architectural Science Department at Ryerson University, Canada** has sent a mail in the following manner:

** { (1) (Ref:- Doshi, H. (2016) - Holy CTC Coupon and Recurring Ink Patch on Sequence of CT Coupons, The Collector, Vol. 26, No.1, 2016, pp. 8-10.- Email: by Hitesh Doshi -hdoshi@ryerson.ca) (2) Ref: Printing Registration Related Design Arte facts in Canadian Banknotes, The C N Journal, Volume 60, Number 5, July-August 2015) 

Quote
Hello Mr. Jayaraman, 

Again I bow to your deep expertise in this area. You have imparted some excellent knowledge.

For clarification Canadian Polymer Bank Notes are printed on BOPP by Securency/Innovia.

As I study more notes I am sure to keep all your points in mind. Since I only get to see final produced batches of notes I cannot see the whole sheets. However in bundles of consecutive notes I can see contiguous notes in the same position. Also I have noticed that the Bank of Canada processes banknotes such that in each bundle it is possible to find notes from adjacent positions. In some instances it is possible to find bank notes from the top of the sheet in one column and the bottom of the sheet in the adjacent column.

From serial numbers one can make out that they are from the same sheet. 

Recently I happened to get such a bundle. Your theory of substrate dimension stability appears to hold true in this particular bundle. I will try to scan these notes and send to you for your reference. 

Again thank you very much. You have truly enriched the mind with your thorough and insightful analysis.

Hitesh

Unquote 

Thanks Hitesh for the feed back.

-Jayaraman-