PRINTING

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General instructions Aerocopy carbonless copy paper can be printed in reels and sheets, depending on the type of the printing machine or final product: - wet-offset - dry-offset - letterpress. The paper feeding characteristics of Aerocopy papers can be compared with the characteristics of other 50 g/m2 uncoated papers. When printing it is important to adjust the printing machine to avoid too much pressure damaging the paper.

Paper conditioning before printing

It is recommended to transfer Aerocopy paper to the printing room at least 2 days before starting to print in order to condition it. Converting of paper directly from unloading can have negative consequences, especially in the winter time. Normal conditions for converting are the following:
- temperature from 18 to 24°C
- relative humidity from 40 to 60%.

 

Printing side

When placing the reels or sheets in the printing machine, it is important to turn the printing side upwards. The printing side of the CB-sheet is the uncoated side, while with CFB and CF sheet it is the side coated with CF coating. Aerocopy paper is usually delivered in reels with the printing side outside and in sheets with the printing side upwards.

 

Grain direction of paper

During printing, paper can be fed in both grain directions. With low grammage papers the feeding of paper through the press is better in the long grain direction due to improved stiffness. For small offset, which uses a friction method of feeding, long grain direction is also recommended.

 

Machine adjustment when printing sheets

Before placing the paper in the machine we recommend guillotine trimming of paper which provides better feeding through the machine and better register.

Suction feeding should be even and not too strong. To avoid damaging the microcapsules adjust the guide wheels to the lowest possible pressure.

Side guides should also be adjusted to minimum pressure.

To ensure even positioning of paper to the printing cylinder set the grippers evenly.

 

Machine adjustment when printing reels

In order to prevent possible damage to reels it is recommended to place a thick foam mat in front of the reel stand.The same is recommended for the reel up stand if reel to reel printing is taking place.

Avoid high tension when feeding paper through the machine.

Eliminate too strong or uneven pressure to:
- drive cylinders
- guide cylinders
- printing cylinders
- guide wheels.

We recommend the installation of guide wheels on the sides of the printing matter.

Eliminate any kind of excessive friction on any part of the machine as this could cause mechanical damage to the CF and CFB coating. Damage to the CB coating can reduce the copying capacity or can cause activation of paper. Damage on CF coating can cause dusting.

 

Offset print

Aerocopy carbonless copy paper in reels or in sheets can be printed on all offset printing machines either in wet or in dry offset. You have to consider the fact that you are printing coated paper with special characteristics and prepare the machine adequately before printing.

In addition to the basic printing instructions the following has to be considered: Pressure between the rubber blanket and printing rollers: In order to achieve good printing results it is very important to adjust carefully the pressure between the rubber blanket and the printing roller, as too high or uneven pressure can have adverse effect on carbonless copy paper. You can test the pressure between the rubber blanket and the printing roller by a simple method i.e. let the CB and CF sheets run simultaneously through the press. The image which emerges should be even and hardly visible considering the trim. If the pressure is not adequate the following problems can emerge:

- reduced copying ability due to damage to microcapsules.
- slight activation of the coating throughout the whole or only part of the printed matter which is usually visible after a delay.
- dust from CF coating.

Printing ink tack:
The use of medium and low tack printing inks is recommended. Too high tack can have negative impact on printing quality and can cause deposits of coating on the printing parts of the blankets. We recommend using an additive in order to reduce the printing ink tack.

Damping Solution:
Minimum moisture applied to the offset plates is recommended in order to avoid dimensional instability of paper. The moisture solution should have a pH between 5.0 - 6.0.

Rubber Blankets:
The use of softer rubber blankets is recommended (from 78 to 80 acc. to Shore).

Letterpress

The letterpress process is also suitable for carbonless copy papers. It is specific for good ink coverage and quality of print.

In addition to the general instructions the following characteristics of this techique shoud also be considered when printing on carbonless copy paper:

Inking:
Minimum inking is recommended.

Pressure on printing surfaces:
Pressure is usually greater with the letterpress process compared to offset printing which therefore can cause damage to CB coating. Reduced copy image is not a problem as generally there is no need for copying in areas of text, lines or tables. Only in the case of screened areas could a problem arise. As a result of too much pressure the microcapsules can be ruptured which then creates slow diffusion of ink to the surface which causes light colouring. Therefore printing with minimum pressure is recommended.

Printing of solid tint:

The printing of solid tint or tinting part of the surface is not recommended due to the following reasons:
- damage of CB coating due to strong pressure caused by letterpress technique and thus causing reduced copying ability
- the large amount of ink applied to the surface with the letterpress proces creates a mechanical barrier on CF coating.

 

Printing of solid tint

Printing of solid tint on CFB and CF paper is usually permitted but only on those parts where copy is not demanded which must be considered, especially when printing in letterpress.

When tinting with the use of offset process check the copying capacity after printing but during printing consider the following:
- application of transparent inks
- maximum coating thickness up to 3 microns.

A very efficient method of tinted carbonless copy papers on either one or both sides is through the use of tinting units on reel to reel printing machines. In this case non pigmented inks are used which allow very thin coatings.

Printing of screen tint

When tinting surfaces with a screen it is recommended to use wet or dry offset considering the following parameters:
- use of 40-line screen
- 20 to 40% screen tint value
- maximum ink thickness coating up to 3 microns.

Printing on back side

Printing on the back side of CF paper can be done in the same way as with non-coated papers. With CB or CFB sheet it is important not to damage the CB coating during the printing process. Too thick coating of ink could also have a negative impact on the copying capacity. This danger is more characteristic for letterpress while in offset it is not so evident. Therefore it is recommended to print in offset on the back side and consider the following:
- adjust the pressure to minimum
- use minimum ink flow
- use fine or normal type
- use lighter colours to avoid the print begin visible on the front side.

Numbering nad printing of sets

Carbonless copy paper sets can be numbered by "crash" printing technique or additionally, running the sets again through the press.
The pressure on the first sheet causes a copy on the other sheets of the set. Sets of 1 + 4 copies can be numered in this way. For larger sets it suggested that tests are carried out considering diffrent types of printing presses.

Not only numbering but other printed matter can be printed in such way.

Desensitisation

If it is required that some part of the form is to be without copying ability, such area can be made insensitive by printing it with a desensitising ink.
Desensitising ink is a special printing ink whitch prevents copying on CF side of the sheet. It is applied only to the front side of CF or CFB sheet but never on CB sheet.

Desensitising ink can be printed on web and sheet offset machines in wet or dry techniques. When printing letterpress it is recommended to use rubber cliches or minimum pressure which still assures good imprint but prevents rupturing of the microcapsules on the back side of the CFB sheet.

Desensitising ink is usually printed on the last printing unit or as a final print on one colour machines. The thickness of the desensitising ink is of major importance. Very thin ink does not assure complete desensitisation, while too thick inking can cause migration or set-off. We recommend that you start printing with a minimum coating and increase it according to the test results of desensitisation.

Testing of desensitisation is performed one minute after printing by writing on CB sheet and evaluating the degree of desensitisation. In case the copy is still visible the coating of desensitisation ink must be increased but when no copy is visible optimum coating has been obtained and you can start printing. It is important to check the blocking results and pay attention to ensure a constant and even application of the ink.

When using desensitising ink it is better not to have polyurethane cylinders.

Desensitising ink has a shelf life of 2 years if stored at normal conditions and in well closed packaging.

Black-outs

In addition to the neutralisation described previously it is also possible to make a copy illegible by black-outs. In practice this can be done by: - printing on certain areas of the CF or CFB sheet - printing on complete top side of the CB sheet and on back side of the CF sheet in order to prevent show through of the data (e.g. data mailer forms).

We recommend printing:
- non defined pattern, or numbers
- with a darker ink or with the ink similar to the copy colour
- offset print because of lower pressure and lower inking.

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