Screenprinting

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This text is currently a draft of a quick quide as part of a zine for Dissident Island. Eventually it will become a stand alone how-to pamphlet. *grammar point: should screen printing be one word or two words?

NOTE: I've moved editing of this document to crabgrass https://we.riseup.net/yummyben/low-tech-screen-printing-a-diy-guide


SUPER LOW TECH DIY SCREEN PRINTING

Screen printing is a relatively easy way to reproduce designs multiple times onto t-shirts and patches, etc. Many people know enough about screen printing to think it requires expensive chemicals and equipment. While photo emulsion, light boxes and squeegies needn't actually be that expensive, there are lower tech approaches which allow you to produce your own screen prints without all the kit and for low cost, if any!

Making your screen

You will need:

  • A frame (or materials to make one)
  • Mesh like fabric
  • A staple gun or drawing pins

The Frame

The easiest way I've found to make a frame requires a drill and a jig saw. Take a piece of 3/4inch ply, chip or particle board (easily found in skips). Cut it down to about 3 inchs larger than the screen size you desire. Drill holes about 1.5 inches from two of the corners diagonally opposite each other (the hole needs to be larger than your jigsaw blade). Now cut in two directions from each hole, parallel with the edges maintaining about 1.5inch clearance. When done, the bit in the centre should fall out leaving you with a one piece frame.

'* Of course you can also make the frames in other ways using what you have to hand. You might also like to try using large embroidery hoops which are cheap to get online or in charity shops/car boot sales etc. Being round brings additional challenges but they offer some potential advantages too.

The Mesh (Silk)

The proper screen printing fabric (not actually silk these days) is fairly expensive. You can however buy enough for perhaps six A4 screens for ~£10 off ebay - or you could save your money for paints and make do with what you can find.

White or lightly coloured is best so you can write on in. It needs to be see-through and when you hold it up to the light you should be able to make out the grid formed by the fibres and the little squares of nothingness between them. The proper stuff generally has 110 threads per inch, thats about 4 per mm but if you find fabric with 2 or 3 holes per mm then you're probably onto a winner. The best stuff I've found has been a fabric used for sheer curtains which I've found by the side of the road three times now. As far as I can tell it's probably a polyester known as 'Chiffon' or 'Organza' / http://en.wikipedia.org/wiki/Chiffon_(fabric). It's cheap to buy if you felt inclined to do so, perhaps £2 per meter - at least a third of the price of the proper stuff.

  • Apparently you can also use old nylon stockings/tights but due to their elasticity they'd work best with small frames, perhaps the embroidery hoop frames.

Fixing Mesh to Frame

Your finished screen is formed when you fit the mesh to the frame which is perhaps the hardest part. Cut your mesh so it's a least 2" bigger all round than your frame. You want it as taut as possible without tearing it, and evenly taut in all directions. Pin or staple down the centre of one side and then pull tight and do the opposite side. Now work towards the corners, doing the opposite each time. Once you have two sides, repeat the process with the other two. It takes some practice.

Your Artwork

You will need:

  • An idea
  • Wood glue and/or acrylic paint
  • A small fine paint brush

Making your artwork screen ready

This method lends itself best to fairly simply and bold designs. You can still get pretty intricate if you have plenty of patience but things with lots of detail or small writing will be pretty tricky and best done using the photo exposure technique. Basically, don't try to be too ambitious!

Screen printing requires mono tone artwork. Either ink is there or it is not, there are no in-betweens so no greyscale. Basically you need to produce black and white line drawings. If you want shading then it has to be done with cross hatching or dithering with dots. If you were working with digital images then filters in applications like photoshop, will allow you to convert a colour photo into a mono-tone line drawing. You can also apply half-tone filters which convert the whole image into a matrix of different size dots but such artwork would be impractical for the technique described here and should be reserved for photo exposure.

Transferring artwork to screen

No printers, photo emulsion, darkrooms or light boxes - you simply paint your design directly onto your screen. You start by simply drawing the design onto the mesh with a soft lead pencil or felt pen. This can be either freehand or by traced. You can even trace directly off a computer monitor and scale the image exactly to the size you need. If your computer monitor is smaller than you need, don't worry, just zoom to the size you need and trace in stages to get the full image.

Positive or negative

Once you have the outline on your screen you'll need to decide which bits should be painted. You are going to paint out the parts of the design where you don't want ink to pass when you print. So, if you were printing a smilie with two eyes and a mouth in a solid circle, you could either paint the eyes, mouth and everything around the outside of the circle (ie. negative), or you'd just paint the inside of the circle while carefully avoiding painting the eyes and mouth (positive). Mostly you'd want to produce a negative but sometimes it is easier to do all or some of the design as a positive. Think carefully about what this means and perhaps modify the artwork so that some bits can be done as positive if need be.

  • I've used wood glue (not clear setting) and also acrylic paint to do this bit. Both seem to work fine. Poundshop wood glue does not work, it washes out. Hard-as-nails glue works well but is a little difficult to use when doing fine detail work.

The Printing Process

So, your artwork is on the screen now and when you hold it up to a light you can see where the ink will come through and where it will not. You are now ready to print.

You will need:

  • Ink (Acrylic Paint or Fabric paint)
  • 1-2" paint brush and/or rubber squeegee
  • Access to running water
  • Something to print on

Ink & Substrate

Obviously you'll need something to print on, eg. charity shop t'shirts or scraps of material to make patches. This is known as the substrate. Some materials take the print better than others - t'shirts good, woolly jumpers bad.

You can get special paint for screen printing onto fabric but since this is a low budget guide we'll just use ordinary acrylic which is fairly cheap and seems to be fairly colourfast after curing. You can buy something called 'screen printing medium' which is a retarder for acrylic paint so that it dries slower to prevent clogging.

You need to think carefully about what colour to use as high contrast works best. Black ink on white is really easy (likewise, black on yellow or any light material), while white ink on black is much harder to do well.

  • You can also print on paper so could use this technique to do posters etc. (the posters for the recent No Border camp in Brussels were screen printed by hand). For printing on paper for posters etc, you can probably use cheap poster paint.


Flood and Stroke

Lay the frame on the area of the material you want to print on then load the mesh with paint. It's usually a good idea to put some scrap paper under the material (or inside if printing on a t'shirt etc).

Most people pile up a neat line of ink at one end of the screen and then use the squeegee to spread it over the mesh (known as the flood stroke), but I've taken to brushing it on all over with a paint brush. You then push the ink through the mesh by dragging a rubber squeegee across the screen. This is known as the print stroke but you'll will probably need two or three passes to get this to work right. Avoid doing too many times or you'll force too much paint through and loss detail as the ink bleeds under your design.

  • You can get clever and arty by using more than one colour at a time, creating blends and gradients. This is why I like applying the paint with a brush as I can almost choose which part of the design will be which colour.

Washing the screen

You must not let the ink dry onto your screen! Acrylic paints can dry really fast in warm weather and you might only manage half a dozen print before it starts to clog. In winter we've knocked out over 200 prints without needing to wash the frame. Don't take risks, if it drys then your screen is ruined! You must wash the paint off before it clogs using cold water, preferable a high pressure jet. Hold a finger over the end of the tap or hose pipe and expect to get wet. When it is clean you need to dry it before continued use. You can use a blow heater or hair dryer to speed up the process.

Drying / Curing

Remember to heat the final product if you want it to survive a visit to the laundrette. The ink is not colourfast until cured. You can do this by ironing for about 5 minutes (place a sheet of paper over the design before you do this or you'll be sorry). You can also use a trowser press, or other heating methods if you are clever and careful (we put dozens of patches in an oven).



Appendix

(probably not for the zine)

Intro to how we got into doing this

During 2010, first at the climate camp in Bonn, then in La Harve and then at the No Border camp in Brussels, we've been messing about with a very crude low tech approach to screen printing using mostly found/recycled materials. We've made frames from everything from planks and cut timber, to plywood batons and chipboard. Our mesh has been fabric from a womens blouse, a scarf and sheer curtains. We've variously stapled, gaffer-taped, nailed and glued both frame and mesh and used both woodglue and acrylic paint as block out. Results have varied widely but we've improved massively over time as we've learnt from our mistakes and honed our technique. Nothing we've been doing is new but most people these days use photo emulsion and we thought it would be good to promote this far more low tech DIY approach by writing it down!

Pros & Cons

Here I list some of the pros and cons of using this method rather than photo exposure.

Pros

  • Super cheap apart from the inks
  • More DIY and recycled
  • More sustainable
  • Low overheads in terms of equipement
  • Spontaneous

Cons

  • less flexible in terms of artwork
  • can't just print off digital imagery
  • more labour intensive putting artwork on screen
  • less reliable and predicatable
  • can't reuse screens

Why Use This Method

  • You prefer not to spend much money on this.
  • You don't expect this to become your job or a primary hobby.
  • You don't have a studio and want to do this where-ever and when-ever you like and need.
  • You need something printed today and don't have access to all the kit required for photo exposure.
  • You just want a few dozen t'shirts, armbands, or patches for your affinity group or action.

When to Use Photo Exposure Instead

  • You already have access to the equipment and chemicals.
  • You want intricate artwork or lots of small words.
  • You want to use digital imagery
  • You want to do multi colour prints using colour separations
  • You want hundreds of campaign t'shirts and plan to sell them

Squeegees

We've made squeegees after being lucky enough to find some strips of fairly thick rubber. Proper screen printing squeegees start at about £12 (Speedball 23cm) and even the rubber itself is something stupid like £1 per inch. However apparently you can get by using grout spreader squeegees which cost about £3. We've not yet tried one but they look promising.

http://www.lawrence.co.uk/acatalog/Squeegy.html

google "grout spreader" http://www.wickes.co.uk/Tile-Grout-Squeegee/invt/166161 https://www.toppstiles.co.uk/tprod1196/section46/greybox/

Frames

It's easy to make a frame but it does require some practical skills and tools etc. Even if you started with an old picture frame, you'd still need a staple gun etc. Ready made frames with mesh already attached can cost as little as £15 for a small one (say 10" square). Alternatively you could try using an embroidery hope which are light weight and easy to travel with.

Make Your Own http://www.printcutsew.com/81/quick-and-easy-build-your-own-silkscreen-frame/ http://www.ehow.com/how_10231_make-silk-screen.html http://www.ehow.co.uk/how_6165515_make-wood-screen-printing-frames.html

Pre Made Screens http://www.screenstretch.co.uk/Screen-Printing-Screens/swedish-redwood-screens http://www.lawrence.co.uk/acatalog/Wooden_Ready_Stretched_Screens.html http://www.londongraphics.co.uk/acatalog/Online_Catalogue_Screen_Printing_Frames_and_Squeegees_118.html

Embroidery Hoops http://direct.hobbycraft.co.uk/productdetail.asp?productcatalogue=278262 http://shop.ebay.co.uk/?_from=R40&_trksid=m570&_nkw=embroidery+hoop&_sacat=See-All-Categories

Other online guides

http://community.livejournal.com/craftgrrl/3674467.html http://www.threadbanger.com/post/490/diy-screen-printing-how-to http://www.reuels.com/reuels/Silk_Screen_Printing_Instructions.html http://www.jacquardproducts.com/products/kits/jacquardscreenkit/instructions1.php

Gluing silk to frame

Here is a tip on how to apply pre-cut silk to the frame with contact cement. You will need to leave around 4 inches from each side of the fabric. Mark the existing frame on the silk with a marker but take into consideration that silkscreen does STRETCH. Apply glue on the screen and frame once (let it dry till when you place your finger it feels dry). When it does dry, repeat the process. And now take a wooden spoon or something similar and place a corner of the silk to the one corner and press it hard with that spoon.

Make sure that you DO NOT make contact with other parts (you can place meat paper or anything that will keep things apart). When one corner is done diagonally, do the same with the other corner but try to use force to stretch the silk to the desired hardness.Pull the paper out from the third corner and apply the pressure and try to stretch the screen again. Apply the pressure again so the contact cement (glue) will make a better bond. If you see a light spot, this means that the glue is not holding anything. Apply pressure again and rub down with lots of force. Repeat the same thing with the fourth corner and anything inbetween.

Leave a stretched screen for 24 hours to bond together. The next day cut off the extra silk. Be sure that you are applying glue in a well ventilated space. If you are suffering from asthma or any other difficulty, do not get yourself into the silk screen printing.


Glossary of Terms

(these should probably reflect the terms used above rather than be a general glossary of silk screening terms. perhaps have two lists)


Used here


Artwork - Common term for an image or text that will be used for printing.
 Also may be referred to as “screen art” or 'copy'. Screen art refers to artwork that is already set up for the screen printing process. Artwork in general may or may not be ready to go to screen. It is important to note that you will need your artwork set up correctly to obtain good results in screen printing.


Blend: Simultaneous printing of more than one color of ink on the same screen creating a mixing or blending effect.


Clogging: A condition that occurs when ink dries in the mesh of the screen preventing further ink flow through the stencil.


Bleeding - This occurs when an ink that is printed migrates outside of its intended printing area.

Colorfast: The ability of a garment or print to hold its colors over repeated washings.


Emulsion (or photo emulsion) - A light sensitive liquid chemical that is applied to the screen, it becomes most light sensitive when dry.

Flood and Stroke - These terms refer to the act of spreading ink over the screen and then pushing the ink through the screen respectively.

Frame - The rectangular wood or metal body used to hold the stretched mesh in a fixed position.


Ink - Common term used to describe the printable substance that is used to make a print. In the textile printing business, the most widely used ink is plastisol.


Mesh or Fabric - The material (usually polyester) stretched over the frame through which the ink passes. Woven material make of polyester, silk ,or stainless steel with uniform openings that will be attached to a screen frame.


Frame: The frame to which screen fabric is attached.

Squeegee - Wooden, metal or plastic handled tool with a rubber blade used to drive ink through a stencil by pulling the squeegee across the screen.



Stroke - The pulling of the squeegee across a screen to produce a print.



General

Air-dry: The property of any ink that will dry without the use of heat by evaporation.

Blockout: A substance used to cover pin holes and to block out any area of the screen that you do not want ink to pass through.
 Usually an emulsion like chemical that is most often not light sensitive and used to fill any unwanted openings in your stencil on the screen after exposure and washout.

Build up: Also know as ink buildup. A condition that develops during the “wet-on-wet” printing process in which ink accumulates on the bottom of a screen.


Burn: To expose an emulsion coated screen to a light source to create a stencil.


Coverage - The quality or amount of ink that is laid down onto a shirt when printed through the screen. Also referred to as the opacity.

Cured Emulsion - Emulsion that has been exposed to light. Curing is the actual chemical process by which the emulsion becomes insoluble in water.

Cured Ink - Ink that has been through the oven at about 330 degrees Fahrenheit. Curing is the actual chemical process by which the ink dries and bonds to the shirt fabric.

Coater: A metal trough used to dispense emulsion for the purpose of coating screens.


Colour Separation: The separating of each color in a design into a separate image. Each individual separated color will then be printed in a certain order to reproduce the original composite image.


Composite Image: A combination of all the color separated films.


Digital Imaging: A term used to describe the creation, display and printing of images through computers and related digital equipment.


Emulsion Remover - A chemical needed to remove cured emulsion so you can “reclaim” a screen for future use with new artwork.

Exposure: Exposing an emulsion coated screen to light to create a stencil. Also known as “burning” a screen.

Ink Well - The side of the screen where the ink is placed.

Line Art: Black and White artwork consisting of no halftones or color.

Light Table or Exposure Unit - This is the piece of equipment that will shine light on your emulsion coated screen curing the emulsion, (or not curing the emulsion where your artwork is). This is known as “exposing” or “burning” your screen.

Mesh Count - This refers to the size of the openings in between the filaments of thread in the mesh by counting threads in one square inch of screen fabric, measured in both directions. Lower numbers, like 110, have bigger openings and smaller numbers, like 355, have very small openings.

Pick Up - The ink that is deposited on the bottom of a screen when printed after a color that has already been printed and is still wet.

Scoop Coater - A trough like tool used to coat the screen with emulsion.

Stencil Break Down - This occurs when the emulsion did not adhere properly to the mesh or when the emulsion was not cured properly. The stencil will begin to fall apart and break away from the screen.

Substrate - This is any item that is being printed on. The side of the screen that comes in contact with the substrate in known as the substrate side.

Substrate Side - The side of the screen that comes in contact with the substrate in known as the substrate side.

Washout Booth - The piece of equipment used to wash screens in. It will always have a light panel in the rear so you may see through the screens as you work with them. Several steps in screen printing are actually done here.

Off-contact: A method of screen printing of having a slight gap between the screen and the substrate for improved printability.


Opacity: An ink’s ability to cover the underlying color of the substrate.

Open Area: The area of a stencil that the ink passes through.


Overprinting: Printing one color on top of another color.

Pinholes: Unwanted tiny specs that appear in the stencil after exposure.


Plugging: See clogging.


Retarder: An chemical ink additive that slows down the drying or curing of an ink.
Screen: A wooden or metal frame with mesh tightly attached to it.


Screen Clamps: Mechanical hold down devices used to hold the screen in place for printing.



Sensitizer: A chemical added to liquid emulsion to make it harden when exposed to ultraviolet light.