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Tuesday, October 4, 2011

PRINTING!!!!

PRINTING
Taping the Screen

Your screen developed well,  it is now  dry and  you  want  to start  printing. Before you  start  to print, the screen must  be taped to prevent ink seepage through the edges where the fabric mesh meets the frame. Since tapes vary  in adherence strength and  are affected by the ink chemistry, it is important to choose a tape  that  works with  the ink you  are using.

Use  plastic tape  when printing with  water based ink.

Use  paper tape  when printing with  oil based ink.

Use  masking tape  when printing with  oil or water based inks  but it is not as durable as paper or plastic tape  and  would work only  for short  runs.

Tape Width should be 2” or more. Measuring the tape  length is an important step  in making a neat  and  professional-like screen. When taping the inside of the screen, measure each length from  corner to corner with  a slight overlap. For example: If your  screen is 8” x 10”  measure two  pieces 8 1/2”  and  two  pieces 10 1/2”  for the inside of the screen. Screens are always sized by the inside dimensions. The  outside dimensions will  be somewhat larger and  it is always best  to measure what  they  are and  cut eh exact size.

After you  have  measured and  cut the correct size  length of tape,  adhere half  of the tape  to the mesh and  half  of the tape  along the wood frame (see  diagram). Repeat this  on the outside of the frame, being sure  to cover the entire perimeter on both  the outside and  the inside of the frame.

If you  made the multicolor screens, the images made by the registration pins  can be taped over. If the image is too close to the artwork to be taped, use blockout.







Off Contact and  On Contact

There are two  techniques of printing, namely off contact and  on contact. On contact is defined as follows: When the screen is in the down position or the print  position, the screen fabric is resting on the surface of the item  to be printed. This  needs no special preparation. Off  contact is defined as follows: When the screen is in the down position the screen fabric is prevented from touching the surface of the item  to be printed by a piece of cardboard or other material that  is
taped to the outside of the screen.

Off  contact is usually used  when printing on a nonabsorbent surface such  as paper. Off contact keeps the screen fabric from  sticking to the paper after  a print  is made. When the screen is in the down or print  position and  not touching the surface of the item  to be printed, the squeegee pressure will  push  the screen fabric down. The  off contact will  cause the fabric to spring away quickly from  the paper thus  eliminating a static cling  (See  Diagram). When the print  stroke is complete, the screen fabric should not be touching the print  surface. Prepare off contact by taping a piece of cardboard, about 1/16” to 1/4”,  depending upon  the size  of the screen, to the outside of the wood frame. Experiment to gain  the maximum fabric spring from  the paper without creating too much off contact.




Hinging the Screen



Some screens come with  hinges that  are attached to a separate base. These screen printing units  fit neatly together. Simply screw the hinges to the back  of the base  and  into  the screen, as shown in the Diagram.








For “ T” shirt  printing with  a screen that  is hinged to a base, it is important to make the following variation in hinging. Place a piece of cardboard, the same width as the cardboard you  will  use to insert inside the “T”  shirt, under the hinges that  are attached to the base. This  will  elevate the hinges so the screen hinges will  meet  the base  hinges when the “ T” shirt  is under the screen. By meeting the height of the cardboard that  is inserted in the shirt  the balance in the printing unit  is reestablished.







“ T” Shirt  Printing requires a platen which is inserted into  the shirt  to prevent ink from going through the fabric and  penetrating the back  of the shirt. This  can be made from  cardboard. Cut  a rectangle that  is wide  enough to stretch the shirt  tightly so there  are no wrinkles in the printing area.  It is very  important to keep  the print  area  smooth when garment printing. This cardboard rectangle is removed after  each  print  is made, and  is placed inside the next  shirt  to be printed.



Constructing a Platen For  Monocolor Printing




A more professional platen can be made with  3/4”  plywood with  a Birch or Formica top (See  diagram). Have a lumber yard  cut a 15”  square with  rounded corners so it is easy  to slide  the “T”  Shirt  on. Bolt  a 2x4  to the bottom of the platen. It should be long enough to extend past  the platen so the shirt  can drape, and  so the 2x4  can also be bolted to a table  or a waist-high stationary object. Attach another piece of wood across the top so there  will  be room to screw hinge clamps. Approximately 2” past  the back  of the platen, attach a piece of wood the same thickness as the platen. It should be as wide  as the platen, and  deep  enough to screw on hinge clamps (approximately


4” x 15”).




Constructing a Platen For  Multicolor Printing




The  basic construction remains the same as the monocolor platen;
however, instead of using hinge clamps to hold  the screen, the 3 point contact bar system is used. Since the platen
and  the screen sit on the 2x4,  the contact bar must  be thicker in this  case so the eyebolts can butt  up against it. To calculate the thickness of this  bar, simply add  together the thickness of the screen wood and  the thickness of the platen.








Constructing a Table For  Monocolor or Multicolor Yardage Printing

To print  yards of fabric with  specific pattern repeats a long  table  must  be available or constructed. It must  be wide  enough to hold  the screen and  the contact bar. The  contact bar must
be screwed or taped securely to the back  of the table. On top for the contact bar,  attach bolts  which will  serve as register stops for the pattern repeat and  for multicolor registration. These bolts
should be placed at intervals of the desired pattern repeat. The  thickness of the contact bar must  be equal to the thickness of the screen so the L-angle can lock  against the bolt  and  the eye-bolts can butt  against the contact bar (See  Diagram).



Page 20




Preparing Registration

Registering the Screen for Monocolor Printing on Paper




When printing one  color on paper, you can use a screen with  hinges attached to the base or you  can use hinge clamps. When the screen and  base  are purchased as a unit  and  the hinges are attached to both  parts, you  cannot move the screen so the stock must  move to be centered. When printing an edition of paper prints, it is important to have  registration guides that  enable you  to print  the same image on different pieces of paper in approximately the same position. Once you  find  the place on the paper where you want  the image to print, make an L shape and  an inverted L shape in each  corner of the paper on the printing base. Tape  will  work nicely as a
paper guide. Now  you  can print  repeat images on different pieces of paper in approximately the same position on each  separate piece of paper. Place each  piece of paper within the L guides to print  in consistent registration.

If you  choose to use hinge clamps you  will  need  to screw them  into  the printing table  or you  can use a C-clamp to hold  the back  of the hinge clamp to the table. Hinge clamps will  enable you  to move the screen vertically or horizontally but this  is not crucial for monocolor printing.

Registering the Screens for Multicolor Printing on Paper




When printing more than  one  color on paper, hinge clamps will  work better and  give  you  more flexibility since they  allow you  to move the screen horizontally and  vertically. Hinge clamps prevent the loss  of registration and  make it easier to print. Once tightened, hinge clamps lock  securely and  do not slip while printing.


To register the screens you  will  need  to center your  main  acetate or outline (let’s call  this the master) to the center of a piece of the stock you  are printing on. This  will  serve as a master for registering all the colors and  traps.

Place this  master sheet on the printing table  and  register the first  screen to it. Be sure  to
print  light  colors first  unless your  design calls  for an opaque light  color on a dark  ground. Check to see if the screen image lines  up with  the acetate or master image. Be sure  to leave no spaces between colors when they  are supposed to meet. This  is when the traps  you  made as artwork are necessary. Move the screen horizontally and  vertically to achieve the maximum overlay coverage.




Once you  register the screen to the artwork, make a paper guide by placing an L and  an inverted L on the printing base  where both  lower corners of the paper rest.  Now  you  can begin to print. Paper is printed wet  to dry so you  will  need  to wait  until  the first  color is dry before you print  the second color.

To print  the second color, place the master sheet within the guides. Now  line  the second screen up to the artwork, aligning the design so no spaces appear between the colors where they are supposed to meet. Make doubly sure  of the registration by placing a dry print  under the screen and  seeing if the image falls  in the right  place. If not,  make the necessary adjustments, tighten the hinge clamps and  print.




Before you  begin to print, tape your original drawing to the print base. Take your  first  screen, place it loosely in the hinge clamps and  move the screen so the image lines  up with  the portion of your original design that  is to be printed. Now  tighten the hinge clamps. Replace your  original drawing with  the stock that is to be printed. Always register stock by placing L and  inverted L in lower corners on the print base. This  is to ensure that each  piece of print stock sits in the exact same place for all colors. If you  are not careful enough to place each  piece of
stock within these guides the successive colors will  not line  up properly and  they will  be out of registration.







Registering the Screen for Monocolor Printing on Textiles






When printing one  color on a “T”  shirt, simply center the shirt  under the image and  tighten the hinge clamps. If you  are using a stationary screen and  base, center the shirt  under the screen. When printing this  way be sure  the entire image prints before lifting the screen because the shirt  will  shift  on the cardboard. Make test prints to get the feel  of laying down the ink before using your  good  stock.

Always use an adhesive when printing on textiles to prevent movement of the garment when you  lift the screen. CrownTM Table Adhesive works very  well  and does  not stick  to the garment. Simply apply a few  drops to the printing area  and  allow to dry to a tacky finish. Then place the textile down without creating any  wrinkles. Wrinkles will  stop  the ink from  printing properly and cause uneven deposits.




Registering the Screens for Multicolor Printing on Textiles

If you  are using the homemade Eye  Bolt  and  L-Angle system, you  will  need  help  printing. Since textiles must  be printed wet  to wet,  you  will  have  to remove each  screen and  replace it with the next  color screen. This  might be difficult for one  person to do without having the ink dry in the screen or without having to lay the screen down.

If you  are printing alone you  must  create a setup area  where each  screen would be easily accessible without wasting time  and  energy looking for screens. A bridge table  set up next  to your printing area  where the screens can be propped up between prints will  do fine.

Have the shirts ready and  close by. Mounting adhesive is necessary to keep  the garment from  shifting while printing and  now  is the time  to apply it. You  can use a hair  dryer to speed up the drying time.

Since you  took  the time  to use the 3 point contact system to register the screens to the artwork when you  exposed the screens, they  should now  be in perfect registration for printing. In the diagram shown, the colors that  are going to print  are green for the leaves, red for the apple, and black for the overall outline. To determine your  print  rotation, start  by printing light  colors and work toward dark  colors. Of course careful examination of your  art work will  determine which colors overlay or print  over  each  other. In this  example, the green would print  first,  the red second and  the black third.






Slide the shirt  onto  the platen with  the collar towards you  and  smooth out any  wrinkles that  might appear. Take  your  first  screen, in this  case  the green leaves, and  check for placement on the garment before inking the screen. Note: The  screen must  make 3 point contact with the contact bar.  If you  need  to adjust the shirt  do so now.  If you  are ready to start  printing, pour  ink in the screen, make a flood stroke and  then  make a print  stroke. Usually, the print  stroke is made towards the printer; however with  the eye-bolt L-angle system the print  is made away from  the printer to prevent the squeegee from  pulling the screen away from  the contact bar.  If the screen is pulled away
from  the contact bar,  the print  will  be out of registration and  it could also  create a blurred image.



After the print  is completed, lift the screen gently and make a flood stroke. Without putting the screen down on the shirt  again, check the print. If the image does  not look complete put the screen in the 3 point contact position and  make another print  stroke, being sure  to print  away from yourself. If the print  looks complete, prop  the screen on the work table  so the outside of the screen does  not touch anything.



Now  you  are ready for screen number two.  In this example, screen two  is the red apple. Repeat the process exactly the way  you  printed screen number one.  Take  the second screen and  place it in the print  position over  the first print, in the 3 point contact position. Check to see if the
first  print  aligns with  the second screen. If the screen needs minor adjustments, simply turn  the eye-bolts in or out to fine  tune  the image. If the first  print  aligns with  the second screen then  ink the screen and  print  away from  yourself exactly as you  did with  the first  screen.



Finally, repeat the same process with  the third screen, which in this  case  is the black outline. Be sure  this last outline fully  covers the image. Here  is where the traps become relevant. The  last screen should also  pull  the print together and  reward you  for taking the time  to properly complete each  step.




It is not recommended to print  more than  three  colors at a time  with  this  3 point contact system, because the time  between prints could cause the ink to dry in the screen.

Register the Screens for Monocolor or Multicolor Yardage Printing

When using the 3 point system for yardage printing, you  have  a choice of printing wet-to- wet  or wet-to-dry. For instance, if the table  is long  enough you  can print  one  color, making all the prints along the line.  You  can clean the screens and  allow the prints to dry and  then  follow with  the second and  third  screens, waiting between colors. The  technique is always away from  yourself.

The  number of repeats of the pattern can be controlled by the distance between the bolts  on the contact bar.  It is quite  common for professional screen printing shops using this  technique to work in teams. This  technique is still  widely used  today. For example, three  colors might be printed by three  persons following each  other down the line,  printing a separate color. Note: If the repeated images are too close to each  other the bottom of the screen may  interfere with  the previous print.

Printing Techniques

Now  you  are ready to print. Actually the printing stage is the easiest of all the work you have  done  and  the most  time  consuming to perfect. Using a narrow blade spatula, scoop some ink onto  the screen just  below the image area.  Raise the screen slightly and  spread the ink over  the entire image area  with  your  squeegee. Press lightly; the object is to cover the image with  ink, not to push the ink through the screen. This  is called the flood stroke.








After you  have  flooded the screen with  ink,  lower the screen onto  the textile or paper and run the squeegee down the screen. Apply more pressure; the object is to push the ink through the screen and  onto  the stock. This  is called the print stroke. Paper printing will  require less pressure than  textile printing because paper is a nonabsorbent surface. Angle the squeegee with  the handle toward your  body. The  squeegee should be comfortable in your  hands. Always use two hands for uniform printing.







Lift  the screen slightly and  push  the ink back  up to the top or flood stroke. Remember to press lightly when flood stroking. Do not move the stock until  you  have  checked the print. If the image looks complete, remove the stock. If the image does  not look  complete you  may  want  to overprint. When overprinting do not remove or move the stock, simply lower the screen and  try again. Always remember to flood stroke.

It takes time  to develop a good  printing technique. Observation and  practice will  turn  you into  a good  printer, so print, print, print!

Always test  print before production runs. Use  scrap paper or textile to get the screen going before you  use your  good  stock.

Cleanup.

Scoop all ink out of the screen with  cut cardboard pieces. Return unused ink to the container; never waste ink!  Remove the screen from  the hinges or hinge clamps. Clean the screen according to the instructions on the ink can label. For example, water based inks  require water cleanup with  a spray hose. Oil based inks  require solvent cleanup. For solvent cleanup, place the screen on a stack of newspapers and  pour  some screen wash inside the screen. Wash it around with a rag or paper towel. Remove the newspapers and  repeat the process until  the image area  is clear. The  image area  is clean when light  shines through when you  hold  the screen up to the light.




TROUBLESHOOTING

THE  FOLLOWING PROBLEMS CAN OCCUR DURING SCREEN MAKING AND PRINTING AND WHAT YOU CAN DO ABOUT THEM


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