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The following tests may be made with
the instrument:
A. Dry Rub
B. Wet Rub
C. Wet Bleed or Transfer
D. Wet Smear
E. Functional Rub
Setup and Machine Operation
Test Specimen
The test requires tow pieces of stock, the test specimen and
a test receptor. Cut a test specimen, approximately six by
three inches. When printed area permits, the sin inch
directions should be cut across the grain of the sheet, but
must not cross pressed or cut scores.
Prepare test strips of material from the same shipment of
stock used in the test sample. Cleanly cut 2 X 7 inch strips
for the four-pound weight are prepared by placing the strip
face down against the pin of the scoring device and scoring
at the white dot positions to facilitate bending the strip
to conform to the test block.
To prepare samples for the two-pound weight, 2 X 5 ¼ inch
strips are placed face down against the end pin of the
scoring devise an scored at the red dot position to
facilitate bending the strip to conform to the test weight
(See picture tutorial “Test Specimen”).
Operating Procedure
Evaluation of Tests
A practical approach should be emphasized in test
evaluation. Few, if any, inks will pass rubbing, wet or dry,
without a slight transfer of color. Decisions on the
suitability of ink are best made by running comparative
tests, checking an acceptable sample at the same time and
under the same conditions.
A quantitative method of evaluating samples for rub damage
has been developed. The test strip (receptor) is measured
(zeroed) with a densitometer or a spectrophotometer before
the rub test. After the test, the strip is measured again
with either the change in density densitometer) or delta E (CIE
L*a*b spectophotometer) reported. The larger the number, the
greater the rub damage.
Consideration must be given to the time interval between
printing and testing, particularly with slow-drying inks.
Also prints should be protected from dust and dirt between
printing and testing.
An attempt should be made to use test samples which are
representative of the run, i.e., eliminating the use of
sheets with excessive anti-offset materials, or sheets taken
from the top of a load which may have collected dust or
foreign material.
New Rubber Pads
The pads should be changed when they become hard or damaged
from age and use. The recommendation is six- (6) month
minimum. These can be ordered from DANILEE COMPANY. To
replace pads, clean metal surface with solvent such as
naphtha. Remove the protective back from pressure-sensitive
surface. Press this surface to the metal in the proper
location.
Rub Chart
| |
Size of Test Strip |
Suggested |
Strip |
Contact Time |
| |
Block (Inches) |
No. of Strokes |
Nat'l |
Before Rub |
|
Dry Rub-Ink |
4
lb. 2 X 7 |
10 |
test sheet |
0 |
|
Dry Rub-Varnish |
4
lb. 2 X 7 |
25 |
test sheet |
0 |
|
Wet Rub |
2
lb. 2 X 5
1/4 |
* |
test sheet |
0 |
|
Wet Bleed |
2
lb. 2 X 5
1/4 |
0 |
Std Blotter |
4
min. |
|
Wet Smear |
2
lb. 2 X 5
1/4 |
* |
Std Blotter |
0 |
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or Muslin |
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*Repeat one-stroke rubs until
sample fails. |
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