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Terms
Printer's
Complaint Checklist:
Sampling
Procedures
It is the
merchant’s responsibility, with the help of the printer, to obtain
order numbers and physical evidence to accurately demonstrate the
nature of the printing problem.
Here are recommended procedures and the symbol codes, which
will be used throughout this web site for you to use as a guide: |
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Information:
All
information required by the mill should be filled in on the complaint
form. Gather and record
all mill order numbers. Identify
press type, press size, printing sequence, blankets used, dampening
system type and pressroom conditions. |
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Ink from
the Can and Rollers: Ink
samples from the can and obtain fountain will help determine the
condition of the ink as it was received into the pressroom, and
also after it has been on press.
A sample of each of at least for else's should be placed in an air
tight, in a non-porous container and sealed with vinyl or plastic
tape. |
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Printed
Sheets with Original: Room
temperature is imperative to obtain the press sheet or Web signature,
which contains not original defect being described.
When obtaining printed sheets, be sure to collect at least
12 consecutive sheets, including several sheets immediately before
and after the original. Clearly
identify that defect by circling it and staple this sheets together. |
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Unprinted
White Paper:Web
and sheet-fed
Samples
of the unprinted paper, which have not been through the press, should
be obtained so a complete analysis can be done at the mill. Sheet-that unprinted and printed sheets should
be wrapped and shipped flat whenever possible. Web paper can be rolled and placed in a mailing tube. |
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Tape-Pulls: When
the press becomes contaminated with material that is causing print
interference, it is necessary to retrieve this material for further
analysis. A recommended material is clear adhere laminating
sheets, which allow the sample to be pulled from the press and rejoined
with a backing sheet which can be then identified as to where the
tape-pull was taken. |
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Fountain
Solution: If
it is necessary to obtain a sample of the water from the presses
water system, be sure to use an airtight plastic container.
Label the bottle as to which unit it came from and include
all information regarding the mixture. |
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Blanket
Smashes:
Send
the damaged blanket along with the tape-pull of the material(s)
that caused the smash. The
certain to roll the blanket and place it in a mailing tube. |
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Photographic
Documentation:
Occasionally
it would be helpful to take a picture of certain paper and/or press
conditions in the pressroom, such as moisture related problems or
excessive piling. If the photo will supplement the other physical
evidence, include it with the information going to the mill. |
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Packaging: Sheet-fed
unprinted and printed sheets should be wrapped and shipped flat
whenever possible. Web paper
can be rolled and placed in a mailing tube.
Be sure the items are properly labeled in accordance with
postal and other applicable transportation regulations. |
Proper
packaging procedures apply to all materials being returned for evaluation.
| Blanket Smashes |
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Description: A compressed or smashed area(s) on a blanket due
to excessive pressure against the blanket's surface in the printing nip.
Causes: 1. Scuffs-a roll-up of paper, usually originating at the
edge of a sheet. 2. Scraps-paper trimmings, folded sheets, labels, packaging
materials etc. 3. Splices in cartons or skids. 4. Folded edges. Possible
Solution: Replace blanket
Precautions:
1. On sheet-fed jobs:
a. The top and bottom sheets in a carton should be removed or examined
carefully before printing because these sheets are the most susceptible
to damage during handling, i.e., scuffs, folded edges, tears, etc. This
is an accepted trade practice.
b. When loading the press, examine the sides of the lift for any signs
of a problem.
2. web Jobs: Roll labels indicate the number of splices
in a roll. The location of a splice it is marked on one side of all rolls.
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Documentation:
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Description: A blister is a bubble-like formation that occurs
on a coated
sheet during drying in a web oven.
Causes: The blister(s) is caused by the "explosion"
which occurs is when the moisture within the sheet vaporizes and cannot
escape through the paper's
coating layer and ink film.
Precautions: When blistering is experienced on press the
following suggestions may help determine the cause or minimize a problem:
1. Determine the paper's surface temperature (PST) as the web exits the
oven, and low where it, if possible, by: a. Decreasing the web speed
and oven temperature proportionately. b. Increasing the web speed. c.
Changing to inks
that have higher tinctoral strength, which would require less heat. 2.
If the blisters are confined to one area of the form, turn the roll around
to determine if the blisters follow the paper, or remain with the press.
Hot spots in the oven can be detected by intentionally scorching the sheet.
3. Check machine roll and roll positions for comparisons, if possible.
Isolating the problem rolls may enable the printer to complete the job. |
Documentation:
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| Contamination |
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Description: Print interference which results in non-print areas or
specks
in printing.
Causes:
1.
Ink Hickeys - Are caused by material,
which is carried by the ink, and are not particles, which originate from
the paper. Possible sources of the ink
hickeys are pieces of ink skin, uncooked resin in the ink or roller
fragments from a dry or deteriorating rubber ink roller.
2. Pick-outs
and Coating Lumps- Are agglomerates of fiber
coating material that are poorly bound into the paper coating or adhered
to the paper's surface.
3. Coating
Pick- Also referred to as" Pepper Picking," is the result
of the lack of the ink exceeding the cohesive binding strength of the
coating materials.
4. Wood
Vessel Segments- Are fibers
which, because of their composition, are difficult to remove during pulping
procedures, and tend to be poorly bound into a coated paper.
5. Occasionally the print can be disrupted by fibers,
which have contaminated the system. In general, fibers
are water receptive and reject
ink. These fibrous materials will adhere to the blanket or plate
and except water but will not take on any ink,
and will therefore cause in the print in the form of its own shape.
6.
Pits May be described as indentations or wells in the surface
of the paper or plate. Pits
cause specks
in print because the ink for rollers cannot apply ink down into the
pits
in the plate; and the blanket cannot apply ink down into the pits on the
paper's surface.
7. Loose
surface dust on paper is a major cause of specks
in printing. When the loose dust sets on the paper's surface, it
prevents the ink
from reaching the sheet and sticks to the blanket.
8. In both sheet-fed and web printing the interaction of ink,
fountain solution and paper must be kept in proper balance or a printing
defect will occur which is commonly referred to as water
interference. Water
interference manifests itself as white specks in print, and tend to
originate from three different sources:
Ink-water emulsification rates
Paper-receptivity to water
Fountain Solution-Wettability
9. Specks
in printing caused by anti-offset
spray will occur in the sheet-fed printing and are normally a
result of running too much spray. The excess spray will interfere with
subsequently applied ink.
10) Piling
is a build-up of ink and/or paper the team real on the blanket during
printing. There are three common types of piling: Image area paper
piling Image area Ink piling Non--image area piling |
Documentation:
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Description: Calendar cuts are small cuts or slices in the paper.
Causes: Wrinkles or creases in a roll of paper that is passing through
a calendar stack under high-pressure may result in cuts along the wrinkle
or creases.
Possible Solution: The calendar cuts may be isolated
to a particular roll. If this roll was sheeted into a palette or skid
at the mill, then, the problem may only affect a small portion of a certain
palette or skid. Every sheet may not have the problem. Calendar cuts
usually have a recurring pattern example, every third, fourth, fifth sheet,
depending on the number of roles sheeted into the palette or skid. Mill
order numbers and put up numbers will help identify the extent of the
problem. Nothing can be done about calendar cuts, except to sort them
out or reject the paper. |
Documentation:
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Cracking
or Tearing at the Fold |
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Description: 1. Cracking at the fold (CAF) occurs when the coating
fractures as the sheet is folded and can be a problem in both sheet-fed
offset and web offset printing.
2. Tearing at the fold (TAF) occurs when it printed and folded job falls
apart to along a folded edge or around the staples after binding. TAF
occurs most often in web offset
printing.
Causes:
1. CAF can be caused by:
A. Attempting to fold heavyweight papers without scoring.
B. Improper scoring.
C. Low moisture conditions.
D. Improper folder nip settings.
2. TAF can be caused by:
a. Excessive heat in the web oven.
b. Weak paper.
c. Improper folder setting.
d. In adequate to chill roller temperature.
Precautions
1. Crack at the Fold It is recommended that papers
100 lb. and up in basis of weight is scored prior to folding.
2. Tear at a folded
a. web exit temperatures should be run at the minimum necessary to dry
the ink.
b. Folding units should be set properly to place minimum squeeze, and
the Tucker blade adjustment should be accurate so as not to shear the
fold. |
Documentation:
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Description: Paper
peeling apart or separating from within. Note: Do not
confuse delamination with blistering in web printing. Blisters all occur
in the oven. Delamination occurs in the printing units.
Causes: If the internal bond of the paper
cannot withstand the tack, or printing forces, during printing,
the sheet will separate or delaminate.
Possible Solution: In general, the only viable solution is to reduce
the tack of the ink being used. An alternative would be to run another
lot of paper. |
Documentation:
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Description: Mottle is a phrase used to describe non-uniform ink
lay or when the printed reproduction has a pattern, which is not present
in the original artwork.
Causes: Mottle can be due to several ink-paper-press
or "system" problems. Among these are:
1. Back trap mottle
2. Wet ink trap mottle
3. Paper mottle
4. Water
interference mottle
Possible Solution: If the printer is experiencing and ink
lay problem the following items should be checked:
1. Inks
should be tack graded to print with the highest tack first
2. Quick release blankets may help minimize a problem
3. The fountain solution should be run with minimum concentrate to run
clean any should be monitored by measuring conductivity
4. Progress of the prints should be pulled to determine which printing
units(s) create the problem
5. All problem-shooting prints should be done at the production speed
6. At least 50 sheets should be turned over and printed on the opposite
side to determine if the ink
lay changes.
7. Another lot of paper
could be run as a comparison |
Documentation:
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Description: Failure of the printed
images to align in multicolor printing
Causes: Misregister
may be caused by a number of factors:
1. A moisture imbalance in the stock
2. Inaccurate trimming
3. Paper slippage in the grippers
4. Loose blanket or plate
5. Improper winding of web roll
6. Improper stripping
Possible Solutions:
1. Care should be taken to allow skid and roll to acclimate to pressroom
conditions while wrapped (sheets and web)
2. Retrim the paper if possible so the grippers and side guide have a
stable edge
3. Try a roll from a different reel position (web) |
Documentation:
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Description: Moisture problems or current due to differentials in
the relative humidity between the paper and its environment
Causes: Paper
fibers
are hydrophilic, or water
loving, and react rapidly to changes in moisture
conditions of their environment. Wrinkling of the stock, which has
absorbed moisture, may develop a wrinkling problem two thirds of the way
back from the gripper edge and continue to the back edge of the sheet.
Tight edged paper, or paper
which has given off moisture,
may create a wrinkling problem in the center of the sheet.
Possible Solutions:
1. When a moisture
problem is encountered, try turning the lift to use the opposite edge
to the grippers. This may eliminate the wrinkling problem; however, this
is usually more successful when encountering wavy edge-type wrinkling
problems.
2. While keeping the stock
wrapped, allow approximately one day for every 10% incremental difference
between the RH of the paper
and pressroom. This will stabilize the paper.
3. Abnormal conditions in this touring of paper
may result in a moisture
related paper problem. Once a skid or carton isd and the stock
is exposed to the atmosphere, it is standard practice to cover that paper
to protect it from climate changes. The presence of moisture
in the offset
printing process, together with the stock's exposure to a different
atmosphere, may cause flat, acceptable stock to react. |
Documenation:
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Description: Picking
(coating pick, Pepper picking) is the result of the tack of the ink
exceeding the cohesive or binding strength of the sheet. Picking
is not lifting coating and/or paper fibers
from the sheet, and can produce non-print areas of various shapes and
sizes.
An original pickout
has depth and a creater-like appearance. The result of this pickout
on subsequently printed sheets isd voids, which show the surface
of the sheet without depth, or merely an unprinted speck in the same size
and shape of the original.
Examination under a printer's loupe, along with a low
angle light, will enable you to determine which sheet contains the
original pickout.
Causes:
1. Insufficient to paper
surface strength
2. Excessive ink
tack or tack-build during printing
Possible Solutions
1. Picking
can be more severe during a make-ready when the ink
and press remain stationary for extended time intervals. This can
be particularly true when a light coverage form is being run. Be certain
enough paper has been run through the press for a system to be stable
before attempting to address a problem.
2. Decrease impression in squeeze to at minimum
3. Before reducing the tack of the ink, have the press person pull progressive
prints, beginning with the first unit, to determine where the picking
is occurring. Once you have determine which ink(s) is causing the picking,
then adjustments to the ink can be made.
For example, if the first down black is causing the pick,
and a print of the black alone shows the picking, then reducing the tack
of the black should improve the problem. However, if the black ink alone
does not cause picking,
but it begins to pick as the additional inks
are applied, then a more appropriate adjustment would be to reduce the
setting rate, or stabilize the ink so that the build-up of tack through
the press is slowed.
4. There are various blankets available in the market. A quick release
blanket could be recommended for a printer with chronic problems. |
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Back to top Setting and Drying
Description:
1. Setting:
Ink setting time is the amount of time required for an ink to gel
or set-up to the point where the sheet can be re-worked through the press.
2. Drying: The process of ink drying involves a chemical reaction that
may require 24 to 48 hours to come to completion.
Causes: It is important to determine if the problem is one of setting
or drying. If the problem is setting, it could be due to:
1. The setting speed or formulation of not ink.
2. A paper,
which has slow ink setting characteristics, may require small lifts, additional
spray,
or longer turnaround time.
3. An improper mixture of fountain
solution concentrate or additives can change the emulsification characteristics
of ink and/or interfere
chemically with the setting and drying function of the ink.
4. Inadequate amount of offset
spray.
If the problem is
drying, it could be due to:
1. The formulation of the ink
2. The improper mixture of the fountain
solution.
Possible Solutions: Normally ink setting and drying problems are recognized
after a job has been printed
on at least one side, which makes and analysis of the printing conditions
at that time difficult. If the job is a work-and-turn form, probably
minimum time has passed since the first side was printed.
Therefore, the precautions to take would be:
1. Check the mixture of the fountain
solution, and get a sample of the solution out of the circulating
tank for further analysis.
2. Obtain samples of the ink from both the can and the fountain so an
evaluation can be done.
Note: Samples must be taken from the press at that time when
the problem occurs.
A note about web ink rub problems: During web printing the setting
function is physical. The solvent in the heat-set
ink is removed by the increase in temperature in the web's oven.
The drying function in the web occurs in the chill roll section
of the press, where the melted ink is cooled into a solidified state.
When dry rub problems occur after web printing, the solutions above apply,
along with the following:
1. Check the paper
surface temperature at the oven's exit to assure that the solvents
are being removed.
2. Check the chill wall temperatures to assure that the paper's
surface temperature is being lowered to 50 to 70°F. |
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Description: A slime hole appears as a hard and brittle contaminant
around a hole in the base stock of the paper.
Cause: Contamination in the fiber
furnish during the papermaking process.
Possible solutions: This problem is not an extensive one and normally
will be confined to a limited amount of paper; example a few sheets or
a small portion of a roll. |
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Description: In web printing, a mill-made splice causes the web to
break as it progresses through the press.
Cause:
Check for:
1. Does the splice have a tail?
2. While his adhesive stock to the preceding the?
3. Where did the break occur?
4. Was the splice marked?
Possible Solution: Web rolls-most roll labels indicate the number
of splices in the roll. The location of the splice(s) is marked on one
side of all rules. This enables the printer to take impression off and
let a splice through the printing nips with minimal waste. |
Comments
on pH and Conductivity |
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A number of fountain solution concentrates being used today are"
combination" type products, which contain all the ingredients, needed
for offset printing.
All that must be added in the print shop is water and if used, is propylene
alcohol.
These concentrates, often referred to as" one-step" etches,
can be a buffered solution. A simplified definition of" buffered"
water mixture would be that you can add either acidic material or alkaline
material to this mixture, and the pH value of the mixture will not change.
Therefore, after a fountain solution has been mixed and placed in the
press, the addition of more concentrate (acid) will not change the pH
of the mixture. However, the acidity of the mixture has been increased.
Using pH as the only measurement of the amount of concentrate in the fountain
is no longer an accurate tool.
An alternative measurement is conductivity. The amount of fountain
solution concentrate in a fountain solution will determine the conductivity
of the solution. Conduct DVD is generally measured and reported in micro
mho/centimeter. The term umho (1/1,000,000 of mho) is used as the measurement
unit of conductivity just like pounds are a unit of weight. Conduct DVD,
or conductance, is the capability of a solution to carry (conduct) electricity
through it. This is the opposite of resistance, which is the property
of a solution to resist the flow of electricity. |
Mailing: Suite #44112 Wexford Square, Brampton, Ontario, Canada L6Z 2W1
Telephone I Fax |
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