| 5T
- 29 T |
Overprint
varnish, sugar decor on cakes and pastry, sealing
pastes, adhesives |
|
|
|
| 34
T - 49 T |
Sports
and travelling bags, coarse fabrics, denim, etc.
|
|
|
| 49
T - 77 T |
Rough,
absorbent surfaces, prints on coarse-grained wood,
flags and pennants |
|
|
| 68/2
HD |
Half-tone
printing in large formats, up to approx. 12 lines/cm
(30 dots/inch) |
|
|
| 77
T - 100 T |
Posters,
large lettering, opaque inks, fluorescent inks,
coarsely pigmented inks, textured surfaces overprint
varnishing |
|
|
| 100
T - 120 T |
Half-tone
screens up to 20 dots/cm, fine lettering and outlines,
solid areas, gauges and dials, sing-printing,
selfadhesive labels |
|
|
| over
130 T |
Fine
line half-tones, step printing, reduced ink deposit
|
|
|
| 110
HD and 120 T |
Most
frequently used screen printing fabrics for universal
applications ; electronic printing (ESTAL MONO
'X', ESTAL MONO, ESTAL METAL) |
|
|
| over
120 T - UV |
UV
- fabrics with reduced colour volume, especially
for printing with UV-inks, also for half-tone
printing and very thin deposits with conventional
inks, i.e. fine line half-tone screen. |
| |
|
| |
Top |
| |
| |
|
100
T - 120 T |
Printing
on plastic bottles and cans, promotional gifts,
pens, etc. For coarsely pigmented and opaque inks,
i.e. white and yellow |
|
|
120
T - 200 S |
Fine
line half-tone screen, reduced ink deposit for
high-speed printing machinery |
|
|
120
T-UV-180 S-UV |
Especially
developed to print with UV-links |
| |
|
Electronic
industry (printed circuits) |
| |
| Top |
| |
| |
| |
Polyester Mono, Polyester Multi Filament,
Polyester Mono Filament
|
| |
Etch
resist |
110
HD/120 T |
|
|
Plating |
90
T/100 T/110 HD |
|
|
Solder
resis 2-comp. |
68
T/77 T 35
pm*
55 T -71
pm*
43 T/49 T/49 S +70
pm* |
|
|
Carbon
conductive lacquer |
38
T - 68 T |
|
|
Marking
print |
90
T/100 T/120 T |
|
|
Removable
solder mask |
12
M/12 T/15 T/18 T |
| |
|
| *
Build-up of conductor lines (height) |
| |
|
| |
Top |
| |
| |
|
Polyester
Mono, Polyester Multi Filament, Polyester Mono
Filament |
| |
|
Etch
resist |
140
T |
|
|
Plating
resist |
120
T |
|
|
Solder
resist |
68
T - 120 T |
|
|
Photo
sensitive solder mask |
28
T - 68 T |
| |
|
| |
Top |
| SMD
- technique |
| |
|
| Polyester
Mono, Polyester Multi Filament, Polyester Mono Filament |
| |
|
| |
32
SL/38 SM |
| |
Top |
| Membrane
switches |
| |
|
| Polyester
Mono, Polyester Multi Filament, Polyester Mono Filament |
| |
|
| Decor
foil |
77
T - 120 T |
| |
|
| Transparent
windows |
100
T - 120 T |
| |
|
| UV-structural
lacquer |
77
T - 165 M |
| |
|
| |
depending
on the structure |
| |
|
| Adhesive |
36
T - 49 T |
| |
|
| Silver
conductive paste |
68
T - 100 T |
| |
|
| Carbon
conductive paste |
49
T - 68 T |
| |
|
| |
Top |
|
Ceramic
printing |
| |
|
| Theads/cm |
|
| |
|
| up
to 20 |
Glaze
printing, coarse, embossed effect |
| |
|
| 20
- 62 |
Glaze
printing, medium fine |
| |
|
| 62-100 |
In-and
under-glaze colours in direct printing |
| |
|
| 68-77 |
Metallic
inks |
| |
|
| 77-165 |
In-and
under-glaze colours in decalcomania |
| |
|
| 90-100 |
Burnished
gold |
| |
|
| 100-165 |
Superimposed
and in-glaze colours in half-tone print/especially
low-colour deposit |
| |
|
| 120-168 |
Bright
gold and lustre preparations |
| |
|
| 12-24 |
Covercoat
(film solution) |
| |
|
| 24-34 |
Covercoat
in general |
| |
|
Nylon
Mono
Polyester Mono Filament |
For
direct prinitng with flat screens |
| |
|
Polyester
Mono Filament
Polyester Multi Filament |
flat
screens |
| |
|
Polyester
Mono Filament
Polyester Multi Filament |
Decalcomania |
| |
|
| |
Top |
| Glass
printing |
| |
|
| 40-100 |
Glass
printing in general |
| |
|
| 100-120 |
Ampoule,
cosmetic bottles, etc. |
| |
|
| 43-68 |
Concealing
borders on automobile windows (solvent based inks) |
| |
|
| 90-100 |
Concealing
borders on automobile windows (UV-inks) |
| |
|
| 77-110 |
Rear
window heating (silver paste)* |
| |
|
| 100-120 |
Antennas |
| |
|
| 40-62 |
Front
panels for household equipment (masks) |
| |
|
| 77-100 |
Front
panels for household equipment (contour/half-tone) |
| |
|
| *)
Special fabric : upon request Estal Vario in various
types |
| |
|
| |
Top |
| Textile
Printing |
| |
|
| Polyester
Mono Filament |
| |
|
| 19
T - 34 T |
Terry
cloth, fur imitations, heavy decor fabrics, denim,
printing of flock adhesive |
| |
|
| 34
T - 49 T |
Decor
fabrics, large areas, over-prints, table cloths |
| |
|
| 43
T - 55 T 34 T - KS |
Smooth
fabrics, |
| 40/2
HD 43 T
- KS |
large
areas, over-prints |
| |
|
49
T - 62 T 34 T - KS
45 T - KS |
Small
areas, motives without fine details, also on thick
synthetic materials |
| |
|
55
T - 77 T 43 T - KS
55 T - KS |
Coarse
half - tones and contours on coarse materials |
| |
|
55
T - 77 T 43 T - KS
55
T - KS |
Fine
half tones and contours on smooth and light materials,
especially synthetics |
| |
|
| 68/2
HD |
Recommended
for the printing of very light and porous materials
which absorb little colour |
| |
|
77
T - 120 T 55 T - KS
90/2 HD
90 T - KS |
For
fine details, half-tones and contours on light fabrics,
especially synthetics |
| |
|
| |
Top |
| Special
applications |
| |
|
| T-Shirt
printing - direct |
| |
|
| Polyester
Mono Filament
40 T - 55 T |
Main
number for lettering and surfaces |
| |
|
| Polyester
Mono Filament
55 T - 62 T |
Fine
contours |
| |
|
| Polyester
Mono Filament
55 T - 77 T |
Single
and multi - colour half - tone jobs We recommend
Polyester Mono
Filament
GOLDORANGE |
| |
|
| Polyester
Mono Filament
49
S |
A
universal fabric |
| |
|
| |
Top |
| Flock
printing direct |
| |
|
| Polyester
Mono Filament
18 T - 32 T |
Flock
adhesive |
| |
|
| Polyester
Multi Filament
32 SL or |
Multi
- colour process |
| |
|
| Polyester
Mono Filament
26 S |
(flocking
through the screen) |
| |
Top |
| Puff-up
colours |
| |
|
| Polyester
Mono Filament
21 T - 49 S |
according
to the desired puff effect |
| |
Top |
| Flock
printing - Transfer |
| |
|
| Polyester
Mono Filament
40 T - 49 S |
for
colour printing |
| |
|
| Polyester
Mono Filament
20 S - 29 T |
for
adhesive printing |
| |
Top |
| Plastisol
printing - Direct |
| |
|
| Polyester
Mono Filament
55 T - 77 T |
for
areas and lettering |
| |
|
| Polyester
Mono Filament
77 T - 100 T |
for
contours and half-tones |
| |
|
| |
Top |
| Plastisol
printing - Transfer |
| |
|
| Polyester
Mono Filament
34 T - 43 T |
for
areas and lettering |
| |
|
| Polyester
Mono Filament
55 T - 77 T |
for
contours and half - tones |
| |
|
| Polyester
Mono Filament
32 T - 40 T |
for
over print |
| |
Top |
| Transfer
printing - Sublimation inks |
| |
|
| Polyester
Mono Filament
77 T - 100 T |
area
printing on transfer release paper with special
inks |
| |
|
| Polyester
Mono Filament
100 T |
fine
lines, half - tones on transfer relesase paper |
| |
Top |
| Glitter
printing |
| |
|
| Polyester
Mono Filament
7 S - 26 S |
Printng
of glitter paste (mesh number according to size
of glitter particles) |
| |
|
| |
Top |
The
difference between multifilament and monofilament
screen printing fabrics |
| |
|
| |
The
synthetic yarns offered for the garment and upholstery
trades (curtains, furnishing fabrics, carpets),
as well as the cheaper stencil fabrics, used to
some extent for screen printing textiles, are
all of mulfifilament (multiple - stand) yarn.
Similarly, the natural silk screen fabrics formerly
used a almost exclusively in screen prinitng are
also multifilament. The best screen printing fabrics,
whether of polymide (nylon) or polyester (Terylene,
Dacron, Tergal, Terital) are all woven from monofilament
(single - strand) yarns. |
| |
|
| |
Owing
to the lower abrasion resistance and the multifilament
composition, mulfifilament yarns in stencil gauzes
are usually thicker than the corresponding monofilament
yarns. Multifilament fabrics for stencil printing
are consequently woven only to 77 or 90 threads/cm
linear; for higher counts the fre printing area
would be too samll and ink penetration inadequate. |
| |
|
| |
Screen
printing fabrics of monofilament yarns, on the
other hand, can be woven up to 200 threads/cm
linear ; even at these fine counts, the free printing
area is still satisfactory. |
| |
|
| |
In
monofilament stencil fabrics ink penetrantion
is better, owing to the compact surface, than
in multifilament fabrics on which ink residues
reamain between the individual filaments and are
difficult to remove. |
| |
In
monofilament stencil fabrics ink penetration is
better owing to the compact surface, than in multifilament
fabrics on which ink residues remain between the
individual filaments and are difficult to remove. |
| |
Cleaning
and re-use far easier with monofilament fabrics
than with multifilament weaves. Multifilament
gauzes are onluy re-useable with restriction weaves.
Multifilament gauzes are only re-useable with
restriction. For these reasons it is not surprising
that stencil fabrics of multistrand, manmade yarns
have hitherto failed to make any headway against
monofilament fabrics. Screen printer clearly prefer
monofilament fabrics. Screen printers clearly
prefer monofilament gauzes. |
| |
Our
monofilament screen printing fabrics are obtainable
in a wide range of numbers, between 2 and 200
threads per cm. |
| |
No. 15 T |
|
No.
200 S |
|
(magnification
approx. 30X) |
The
fabric number corresponds to the amount of threads
per centimeter. The numbres 77 to 180 are very
widely used in screen printing. The most popular
number are 110 and 12. |
| |
Most
of our monofilament fabrics are made in a lighter
and in a heavier grade ; in fact many fabric number
are produced in various graduations. Consequently,
a thinner or thicker ink deposit can be obtained
by selecting a fabrics of thinner or thicker yarn.
Note the technical data in our technical data
sheets and price lists. |
| |
In
other words, the same fabric number, containing
the same amount of threads per centimeter, is
woven with thinner or thicker threads. |
| |
The
screen printing fabrics, therefore, are produced
in the same number in 3-4 grades or qualities. |
| |
|
| |
| Top |
| |
Stabilized
screen printing fabrics of monofilament polyester
ensuring and exact register |
| |
1.
Polyester
Mono Filament,
the classical screen printing fabric is made of
monofilament (single strand) polyester yarn. Polyester
Mono Filament
has a higher abrasion resistance than the multifilament
polyester fabrics hitherto used in textile screen
printing (e.g. Terylene, Dacron, Terital, Trevira,
Diolen, etc). |
| |
2.
Polyester
Mono Filament
has a very high resistance to stretching adn thus
ensures and exact register. |
| |
3.
Polyester
Mono Filament
remains uninfluenced either by usual temperature
fluctuations or by humidity, So that the same
exact register is maintained from beginning to
end of the printing process. |
| |
4.
Polyester
Mono Filament
is indispensable for large-size printing, in particular
for half-tone printing. In very many cases, Polyester
Mono Filament
can replace the usual stainless steel fabrics,
especially in the production of printed circuits,
as well as being suitable for the printing of
qualioty lablel work. |
| |
5.
Polyester
Mono Filament
fabrics are made of first grade, electronically
controlled polyester monofilament yarn and have
the following advantages over metalwire fabrics: |
| |
A
good abrasion resistance and appropriate elasticity
despite high stretch-resistance. Metal suffers
from Polyester
Mono Filament
allows long printing runs and permits sharp outlines
down to the very last prints. |
| |
Unlike
bronze and steel wire cloths Polyester
Mono Filament
is rust- and corrosion-proof and much cheaper
than stainless steel wire cloth. |
| |
Polyester
Mono Filament
is highly wear-resistant and thus more economical
than wire cloth. Whereas wire cloths esaily crinkle,
develop bagging and other defects, Polyester
Mono Filament
fabrics are insensitive to impact and pressure. |
| |
6.
Polyester
Mono Filament
fabrics can be repeatedly stripped and re-used
in screen printing. |
| |
7.
Due to its smooth surface Polyester
Mono Filament
guarantees best in penetration. |
| |
8.
In Screen printing, ink consumption depends principally
on fabric thickness and is much reduced by using
Polyester
Mono Filament
fabrics with their finer threads. This considerably
shortens the drying time. Efficient work, especially
on high-speed automatic machines, urgently requires
shorter drying times. |
| |
9.
Polyester
Mono Filament
lifts off readily from the printing base, avoiding
ink smear, and allows the press to be run at higher
speeds. |
| |
10.
Polyester
Mono Filament
is stretched, cleaned and further processed in
the same manner as the Nylon
Mono
Fabrics, but allows an elongation of approx. 3%
only (as against 3% to 6% for
Nylon Mono),
depending on the fabric numbers. |
| |
11.Polyester
Mono Filament
is available in various widths:
105 cm, 122 cm, 132 cm, 145 cm, 155 cm, 165 cm,
178 cm, 205 cm, 220 cm, 250 cm, 270 cm, 315 cm,
some numbers up to 370 cm. |
| |
12.
Polyester
Mono Filament
is highly acid-proof and not light sensitive. |
| |
| Top |
| |
| |
| |
After
stretching, the screen printing fabric is mounted
on a stencil frame. The permissihble tension depends
on the tearing strength of the particular fabric.
The resistance to stretching of a particular fabric
is a second important factor in ensuring correct
register and in determining the proper distance
between screen and printing stock. |
| |
The
tension is measured in Newton per cm (1 N = 0,102kp)
with mechanical or electronic equipment which
one places on the fabric. |
| |
Optimum
tenisoning force for different fabrics |
| |
The
optimum stretching force to be applied in kg/per
cm of selvedge depends, as said before on the
tearing strength and stretching resistance of
the particular fabric. Modern, monofilament (single-strand)
and multifilament (multiple-strand) synthetic
weaving yarns have a higher tensile strength than
for instance natural silk. |
| |
Nylon
and polyester are nearly alike ; in the thicker
yarns polyester is slightly stronger than nylon,
while in the finer counts nylon is slightly stronger. |
| |
On
the other hand, polyester yarn, and to some extent
also natural silk, is more stretch-resistant than
nylon, however much the nylon is per-stretched
and stabilized. |
| |
Apart
from this difference between the tearing strength
and the stretching resistance of different yarn
materials, for one and the same material it may
be stated in principle that bothe these values
will be roughly proportional to the cross-sectonal
area of the yarn. The cross-sectional area of
a round yarn thread is obtained by the radius
or .785 X diameter squared. This means that a
round thread A of double the diameter of another
thread B of the same yarn material will be about
four times as strong in tearing and stretching.
With increasing thread diameter, therefore, the
strength values increase according to their squares. |
| |
As
we know, stencil fabrics are made in different
degrees of fineness (counts). |
| |
|
| |
The
count represents the number of threads per cm
linear. The counts most used for graphic screen
printing are from No 77 to No 165; for special
uses, e.g. very fine half-tone printing, up to
NO 180. The standard count is No 120. |
| |
Consequently,
the higher the fabric number, the finer the yarn
to be used. |
| |
Moreover,
in the same weave counts (same number of threads
per cm linear count), fabrics can be woven of
thinner or thicker yarns. |
| |
|
| |
Considering
any of the three fabric grades of the same count
illustrated above, i.e. fabrics with the same
number of threads, it is obvious that the grade
HD with the thicker yarn is stronger than grades
T and S with the thinner yarns. This should be
taken into account when stretching on printing
frames. Thicker, and consequently stronger fabrics
can and should be more highly stretched than thinner
and lighter fabrics. In pneumatically operated
stretching appliances, the air pressure should
be increased for stronger fabrics while more care
is needed for the lighter fabrics. |
| |
| Top |
| |
| |
| |
As
mentioned before, it is a well-know fact that
loss of tension of a newly stretched screen amounts
to approx. 10-20% within the first few hours,
depending on the type of tensioning device used,
the original mesh tension, the frame stability
and waiting time before gluing. For printing jobs
with accurate register, therefor, it is recommended
to let the screens rest for a few hours before
stenciling. When stretching frames, please take
into account this loss of tension. |
| |
We
recommend to use the SST-Newtontester whenever
high accuracy of registration is required. |
| |
For
multi-colour work all screens should show the
same tension. A check with the SST-Newtontester,
therefore, is especially important. |
| |
Practical
experience has shown that variations in screen
tension of 1 to 2 N on the same or different screens
are without noticeable influence upon precision
in screen printing. |
| |
During
long print runs of after several screen reclaimings
the loss of tension can amount to several Newtons. |
| |
Please
take care that accurate measurements can only
be attained if the SST-Newtontester is placed
away from the screen frame and the tensioned screen
lies on a horizontal plane. |
| |
| Top |
| |
Adhering
screen printing fabrics onto the frame |
| |
1
Frames |
| |
Note
should be taken of the preceding section on printing
frames. We can summarize this as follows: |
| |
The
side of the frame to be gued must first be cleaned.
Ink and adhesive residues must be removed and
sharp edges and corners of the frame rounded offf.
Certain adhesives can be left on the frame if
the same adhesive is to be used again and if the
coating already applied is sound and flat. |
| |
It
is always advisable to roughen the adhesive surface
of metal, in particular aluminium, using an emery
wheel or emery disc of rough grain. Sand-blasting
of the surface to be glued is also a good method. |
| |
Metal
frames should be thoroughly degreased, shortly
before gluing, with a suitable solvent (cellulose-thinner,
acetone, refined petrol or alcohol). |
| |
On
aluminium frames the oxygen contained in the air
causes an oxide skin to be formed after a short
time. Oxidation will even be increased by the
use of alcali or by an anodizing process. The
surface of the aluminimu is made porous which
improves adhesion. In the case, however, where
the surface was mechanically roughened, the indentations
are etched away to a certain extent by the oxidation,
and adhesion is not improved. |
| |
In
order to stop oxidation it is advisable to cover
the roughened surface by means of a two-component
adhesive, such as COLESTAL. A frame protected
in such a way can be left for a long period. The
subsequent coat of adhesive applied during the
actual stretching operation bonds perfectly with
the precoated frame. |
| |
| Top |
| |
|
|
| |
A
stencil brush with medium hard bristles should
be used. It should be half as wide in diameter
as the width of the frame. |
| |
In
case of poor contact between mesh and gluing surface
of the frame, we recommend placing weights made
of 30 X 30 mm iron bars (see picture). |
| |
|
| |
For
better protection, gummed tapes are additionally
applied on the inside of the frames and also lacquered. |
| |
|
| |
An
elastic sealing paste can also be applied to the
insied corners of the frame, in order to prevent
solvents from penetrating between the frame and
the fabric. |
| |
| Top |
| |
Pretreatment
of screen printing fabrics |
| |
| Roughening
new fabrics: |
| |
For
indirect stencils (photo film and carbon tissues),
we recommend roughening the surface of new fabrics,
nylon or polyester monofilament, once only with
Silicon Carbide No. 500 or finer. Rinse the fabrics
and mark those frames. The silicon carbide is
supplied by the screen printing dealer in 1-kilogramme
packs and is applied to the printing face of the
gauze with a wet sponge, rubbing for 1-2 minutes.
Wash off with high-pressure water-jet |
| |
Do
not use domestic scouring powders!
Such scouring powders are usually not of any standard
grain size, so that scouring particles of larger
size may clog the fine -mesh fabrics, particles
of larger openings and later cause pinholes or
cut the threads of the mesh. |
| |
|
| |
Moreover,
the chemical additives in house hold scouring
powders prevent the adhesion of carbon tissues
and films; whereas the silicon carbide powders
are thoroughly degreased and chemically cleaned. |
| |
Metacresol
1:10 solution in ketone), on the one hand, weakens
the nylon filament to an uncontrollable extent,
and, on the other hand, does not roughen polyester
fiber. We advise against the use of metacresol. |
| |
| Top |
| |
| Printing
requirements: |
| |
-
Lines
Sharply defined are attained with a coating build-up
of 10-18 pm on fabrics with 90 threads/cm and
finer.
Rule-of-thumb for coating build-up: approx. 15-25%
of the fabric thickness. |
| |
-
Half-tones
The thineest possible coating build-up of 4-8
pm results in thin ink deposit required for half-tone
prints.
Rule-of-thumb : approx. 10% of the fabric thickness. |
| |
-
UV-inks
When printing with UV-inks, the ink deposit should
generally be as low as possible. As a rule, the
coating build-up on the print side of the screen
should not exceed 5 pm. |
| |
In
most cases the basic coating is done wet-on-wet.
After intermediate drying, additional coatings
are applied in order to eliminate the unevenness
of the fabric structure. |
| |
The
fineness and the quality of the fabric are the
determining factors for the number of based coatings
of the stencil. |
| Top |
| |
| Finess
of fabrics: |
| |
Threads/cm |
Mesh
Opening |
Open
area |
Fabric
thickness |
| |
|
|
|
Polyester
Mono Filament
120
T |
45
PM |
30% |
61
PM |
Polyester
Mono Filament
150 T |
30
PM |
20% |
64
PM |
Polyester
Mono Filament
180 T |
23
PM |
17% |
62
PM |
|
| |
These
examples clearly depict the different percentages
of open area in fabrics of similar thickness.
The larger mesh opening causes more emulsion to
be pressed through the fabric per coathing. In
order to attain the same coating thickness on
all three fabrics the number of coatings will
vary. |
| |
Quality
of fabric |
Mesh
Opening |
Open
area |
Fabric
thickness |
| |
|
|
|
Polyester
Mono Filament
120 S |
49
PM |
37% |
53
PM |
Polyester
Mono Filament
120 T |
45
PM |
30% |
61
PM |
Polyester
Mono Filament
120 HD |
39
PM |
22% |
66
PM |
|
| |
The
various fabric qualities in the same number also
influence the coating thickness, because not only
the mesh opening but also the fabric thickness
differ. |
| |
| Examples
for cating : |
| |
Quality
of fabric |
Mesh
Opening |
Open
area |
Fabric
thickness |
| |
|
|
|
Polyester
Mono Filament
120 S |
37
PM |
53
pm |
2
+ 2 |
Polyester
Mono Filament
120 T |
30
PM |
61
pm |
2
+ 3 |
Polyester
Mono Filament
120 HD |
22
PM |
66
pm |
2
+ 4 |
|
| |
The
coating of the screen should be done immediately
after degreasing, in order to avoid the fabric
from getting soild (dust, etc.); exception : storage
in dustfree surroundings. |
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| The
fabric must be absolutely dry before coating. |
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| Stencils
for half-tone printing |
| |
| Avoidance
of moire effect |
| |
The
correct half-tone screen rulings and fineness
must be slected according to the size of the print
and the distance at which it will be viewed. |
| |
|
| |
| |
Due
to the uneven structure of the screen element,
there is no moire effect as with line, dot or
bead-string ruling. |
| |
Since
many years there is in textile printing a kind
of graining known as the "DIRACOP method".
For this method the diapositives are prepared,
even today, manually, through the use of transparent
foils with a grained surface in order to attain
the half-tone structure. |
| |
In
photography the graining effect is attained through
the use of a magenta contact screen. |
| |
|
| |
Line
ruling is often particularly suitable for the
representation of engineering objects in monochrome. |
| |
Circular
rulings are suitable for monochrome printing:
they subconsiously lead me eye of the beholder
to a particular image point ; the centre of the
circle. |
| |
|
| |
The
ordinary dot ruling 4-figure symmetry has nearly
50% coverage with nearyl square dots; in the lower
and higher percentage values, dots tend to be
circular shaped. |
| |
This
form of ruling has nearly 50% coverage value,
tend to combine in beadlike strings. This results
in softer transitions than with square dots. which
at more than 50% coverage, combine in both directions.
Bead rulings, for instance, are suitable for portraits
or for the reproduction of a porcelain effect. |
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| |
| Fineness
of half-tone screen and fabric |
| |
The
fineness of the half-tone ruling is always linked
with the fineness printing gauze and the type
of stencil. |
| |
1.
The finest details should properly adhere to the
gauze. The areas with the highest coverage of
ink, especially where the samllest dots of the
emulsion must cling to the fabric, are particularly
critical. The smallest dots should not rest on
one thread or even fall through the mesh opening. |
| |
|
| |
25-line
per cm half-tone stencil on Polyester
Mono Filament
No. 100 HD (magnified 23 X) |
| |
Strictly
speaking, the diameter of the smallest half-tone
screen opening on the diapositive should be microscopically
measured in order to slect the gauze of the correct
fineness. |
| |
In
the above example, the fabric is four times finer
than the half-tone ruling. It is logical that
this fineness is not sufficient for a 94% coverage
(which, one must admit, is hardly ever necessary
in screen printing). For an 87% coverage it is
barely sufficient. |
| |
(The
relation of the printed half-tone coverage to
the 100% coverage is know as tone value.) |
| |
|
| |
2.
Screen printing is a print-through process and
not-as offeset - a transfer process. The screen
fabric of the stencil causes a thicker ink deposit
than a lithoplate. This is the characteristic
and advantage of screen printing, namely, the
intense and effective depth of colour.
In hlaf-tone printing, however, the ink deposit
should be relatively thin, because, the finer
the half-tone ruling and the higher the degree
of coverage, the more difficult it is to avoid
the running of ink in the high-coverage print
areas (smudging).
The thinner and finer the fabric, the lower the
ink deposit, therefore, these fabrics are more
suitabel for fine half-tone ruling. |
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