Dummies Guide to Screen Printing | Wicked Printing Stuff

Dummies Guide to Screen Printing We talk to a lot of people who want to start screen printing but are not quite sure of the process and what’s really involved. So we thought we would write a high level process overview, to give you a little insight into how to get started. If you are a hobbyist, artist or commercial printer, the processes are pretty similar. We are going to work through the process of taking a blank garment to producing a garment with a printed logo………………..more details

via Dummies Guide to Screen Printing | Wicked Printing Stuff.

Proper cleaning preserves your screens Part 5

Screen cleaning&reclaim

The exorcist – how to get rid of ghosting on your screens

When you have finished your screen print run there are a number of next steps.

If you plan to use the design again then you need to wash the screen down. This will remove the ink from the screen but leave the exposed image. If your ink is water based a simple hose down is sufficient but a solvent ink will need screen wash. Make sure to use the right process for the ink involved.

‘Reclaiming’ is the act of striping the stencil from your screen in order to create a new stencil and start the printing process over again. If you are not going to print a design any more it’s time to reclaim your screen so that you can use them for something new.

Remove all tape from the mesh. Apply stencil strip with a cloth to both sides of the screen. Using a power washer to clean the screen thoroughly on both sides. Your screen is ready for reuse.

If there is still an image left on the screen this is called ‘ghosting’, this is an example of a screen with ghosting.

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If there is any ghosting of the screen you can use a ghost remover / haze paste to remove them.

Haze Paste remover is a great solution if you have any ghosting left on your screen which is common when using waterbased inks as they dye the mesh.  Our range includes the premium MacDermid Autohaze will deals with the most stubborn stains.

The finished  screen after using this product  Haze Paste..

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Creating a screen using traditional exposure methods

Where does exposure fit in the screen printing process?

What emulsion should I use?

How long can I keep emulsion?

How do you get rid of pin holes?

How long should I dry my screen?

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Let’s go back to basics. Screen printing is also a stencil method of print making in which a design is imposed on a screen of polyester or other fine mesh, with blank areas coated with an impermeable substance, and ink is forced into the mesh openings of the mesh by the fill blade or squeegee and onto the printing surface during the squeegee stroke.

Emulsion is the means of making impermeable substance. Light sensitive, thick liquid which coats the screen. When the screen is exposed the emulsion hardens and unexposed areas drop out to leave the stencil.

So you have your positive artwork

Making Your Artwork Positive.

Making Your Artwork Positive.

Now this process is one of the most tricky in screen printing and needs to be done thoroughly and carefully. Never skip on any step especially drying.

The first step is to degrease your screen

It is very important to degrease the screen prior to coating the screen with emulsion and exposing the artwork. A screen that is not degreased will have problems exposing and increase the chance of pinholes, the emulsion will not adhere to the screen properly and might washout before the image can be seen. The emulsion could also not wash out at all. Make sure you let it dry thoroughly before you coat it with emulsion.

Choosing your emulsion

There are many emulsions on the market and every printer will have their preferred type and brand. Some emulsions come pre sensitised and ready for use and some will need mixing. Our emulsion is a 2 part emulsion, its comes with sensitizer.

Shelf life is different depending on when the sensitizer is added . Separately both parts can last from 12-24 months. Once mixed the emulsion lasts 6-8 weeks (its life can be prolonged slightly if it is stored in a cold place, like the fridge).
Always make sure you have chosen the right emulsion if you are using Plastisol inks / Solvent inks you need a Solvent resistant emulsion like Ulano Proclaim or if you are using Waterbased inks you need a water resistant emulsion like Ulano 925wr. We also sell Autosol emulsion, which is a good dual purpose emulsion, it can be used with both waterbased and solvent inks.

Location

Make sure you are doing all parts of the emulsion and exposure process in a light safe environment with NO outside or bright light. This includes mixing your emulsion, coating your screens, drying screens, exposure, and washout (as soon as screen is exposed as long as you wash it out straight away this is not a problem)..

A costing trough is the best way to get an even coverage of emulsion. Always check to make sure the coating trough has a straight edge and no damage otherwise you will get poor coverage and you can snag the mesh.

Here are a few things to watch out for if your images are not washing out correctly:
That you are not coating your emulsion too thick. One coat both sides should do it, with a nice even spread. There are sometimes where you may need some extra coats e.g. printing transfers and printing white onto a dark garment but you will need to adjust the exposure time.

Coating Your Screen

Coating Your Screen

That your film positive is very opaque and dark. If you hold it up to a light and can see through it, you need to double print your film to achieve a more opaque image.
That there is positive contact between your screen mesh and your positive film. If the film is not pressed completely against your mesh then you will get light reflection between your positive and your screen which will result in a blurry and not clear image. That’s why the glass is so important.
That you are exposing your screen for the correct amount of time, which will depend on the exposure system you are using. If you are unclear on exposure times please feel free to ask us. The simple run of thumb is – if the emulsions washes off too easily and you start to lose the stencil then the screen is underexposed and if after prolonged washing the stencil does not come through they you are likely to have overexposed the screen.
After you coat your screen, you want it to be COMPLETELY dry  before you expose the screen.

Exposing the image

Exposing Your Screen

Exposing Your Screen

To transfer your image onto your screen you will need to use an exposure unit. There are many different exposure unit set ups on the market and each has a different light source. Each having different light sources. UV, halide and halogen are very popular in the UK. Our Wicked exposure lamp has a 1000 watt halogen light source and is provided will all waterbased and Plastisol kits.

We also sell Actinic and Metal Halide exposure units which are able to expose quicker (typical exposure time is 2 minutes for an Actinic unit and 16 minutes for the lamp depending on size of the screen) than the cheaper lamp solution. Some units include built in drying cabinets making the whole process a lot faster.

A very large part of your decision if you are new to screen printing will be your budget and space. Exposure units vary dramatically in price. The WPS Lamp is small and compact,

After exposing and rinsing out your exposure, you want your screen to thoroughly dry (and ideally harden your screen, by exposing it to the sun or your exposure unit) before inking and printing. This process is often called double baking.

Before inking you need to use blocking tape (can use brown tape or professional blocking tape) to cover up areas on the screen not covered by the emulsion. Also fix any pinholes either using blocking tape or using screen filler which is a liquid emulsion, make sure you choose the right one as there are different versions for solvent and water resistant stencils.

Now you are ready to print

Registering Your Print

Registering Your Print

When you get bigger there are other options like the Revolutionary Riso QS200 Designed for the Professional Printer which prints directly from your computer onto a screen. Then the whole process takes under 5 minutes!

How much space do you need for Weiss screen printing carousel?

Has your business expanded and you need to automate the screen printing process?

Exactly how much space do you need?

This diagram shows the exact requirements

 

The Ergo-Printer 2013 model can be used as a low volume manual or high speed semi-automatic. Using two automatic heads, one operator can print 300 pieces per hour and two operators can print 500 pieces per hour. 4-colour process work can be printed at 300 pieces per hour with two operators.

via weiss screen printing carousel.

 

What screen printing ink should I use? Water, Plastisol or Solvent

Are you confused which screen printing ink to use?

Inks &aditives

You do need to spend a bit of time assessing which is suitable for your product and we would be glad to help and advise you. This is a little starter to you can do some more research on our website.

Waterbased Screen Printing Inks

  • An ultra safe product suitable for use on children’s clothing including babies
  • Suitable for use in school and colleges
  • For paper screen printing
  • Can be air dried.

Plastisol Screen Printing Inks

  • Will print on any porous surface
  • Easy to print with
  • Eco Versions available
  • Great colours on dark garments
  • Specialist Inks like glitter

Solvent Screen Printing Inks

  • Will print on non porous surfaces like metals and glass
  • Suitable for unusual substrates
  • For professional use

That gives you a start so you can start choosing the right ink for the right job. But remember we are only a phone call away should you want advice

The Ink is not giving a 100% coverage over my print?

The Ink is not giving a 100% coverage over my print?

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Check that you have the proper off contact for the job at hand and that the screen is parallel to the platen. Typically you want your screen to be about 2 pennies or an eighth of an inch off your application.

If that is ok, assess the squeegee you are using – is it too soft for the ink type and mesh count too high?

Plus always remember to flood the image before you print.

via Wicked Printing Stuff, your home for screen printing equipment and supplies – FAQs.

The Cure

Heat curing equipment_2

When do you need heat/drying in the screen printing process?

•    Drying emulsion before exposure
•    Drying your screen after washing off the emulsion
•    Touch drying after printing
•    Drying between colours
•    Fixing ink to fabric, The Cure

N.B. For printing posters and paper type flat work, you would use poster ink which is also an air dry ink. Either of the two textile inks may be used for screen printing shirts but the poster ink is used only for flat work and graphics printed on porous or glossy paper materials.

Drying emulsion before exposure

Screen drying cabinet or overnight, must be dust free and dark environment

Drying your screen after washing off the emulsion

You can blowdry it, or wave it in the air outside, or just let it air dry, but you should let it dry before making prints.

Touch drying after printing

Flash dryer, hand curer or heat gun

Drying between colours

Flash dryer, hand curer or heat gun

How hot does The Cure have to be and how long does it take?

Once you have finished your print, you will need to fully cure your garment. Simply drying the print does not mean that your garment is machine washable. In other words – The print will come out in the wash! The temperature must get hot enough to firstly evaporate the waterbased medium, then set the pigments.

This is a guide only
150F [66°C] Water begins to leave the ink
200F [94°C] Binder reaches lowest viscosity and maximum surface contact is made with the fabric
220F [105°C] Water begins to leave the ink rapidly
270F [133°C] Fifty percent of the water is gone and the binder and pigment start to cure
300F [150°C] Most of the water is gone and the binder-pigment combination is partially cured
300F [150°C] [for 30 seconds to a minute] Binder and pigment is cured

If you have used water-based ink:

Although waterbased ink dries to air, it takes a high temperature to cure water-based inks. You can cure the ink at 165°C (some are hotter) by using a flash dryer, tunnel dryer or heat press.  It can take up to 2 minutes to cure waterbased inks.  If you mix a catalyst with the ink you can cure the ink with a heat gun – but remember only really suitable for cold washes.

WPS waterbased inks need to be cured at 165 degrees or above.  To cure your inks, you have a number of options. You can use a flash dryer, hand curer, heat press or tunnel conveyor dryer for this.  If you are using a WICKED PRINTING STUFF flash dryer to cure your print, we recommend you measure the temperature of your print with a digital laser thermometer until it reaches the required temperature. Remember that it is important that the entire ink film thickness reach the specified cure/fusion temperature. Depending on the nature of your fabric it is recommended that you break this up into intervals of approximately 10-15 seconds and repeat 3-5 times as most garments cannot withstand such continuous heat in one go. If you are a busy printer, you will find that a conveyor tunnel dryer is a much quicker, more efficient and reliable way of curing prints.

If you have used Plastisol or other solvent-based ink:

In between the application of the different colours of your design you can use a heat gun to flash dry but to fully cure you should use a tunnel dryer, flash dryer or heat press.  The ink needs to get to 150°C for typically 60 seconds.  Glitter, reflective and white ink can sometimes take longer.
If you are printing more than one coat of ink for the same image, or printing a multi-colour image, you will need to flash cure your ink by using a flash dryer, hand curer or heat gun between each print. Flashing enables you to print one coat of ink on top of another – e.g., a color on a white base. You also might flash an ink to keep wet ink off the back of your screens. Some inks, such as glitters, metallics and high densities, are not designed to be printed “wet-on wet”. They should be “flashed” when printing in sequence. Once your print is dry to the touch you can apply your second coat or next colour.  Most inks will “gel” (flash) when the ink film reaches 220°F to 230°F (104°C to 110°C). There are 3 factors that affect the “gel” or “flash” of the ink: the temperature of the flash, the distance of the flash from the printed image, and the time the printed image is exposed to the heat. As a rule, you want to flash the ink film until it is just “dry to the touch”. Over-flashing inks can cause inter-coat adhesion problems and make the inks very “tacky”. Check your flash cure unit to see if it has temperature and airflow controls. These can help you better control your flash cure process.

 

All Plastisol inks will not air dry and will therefore need to be dried by heat equipment. Plastisol inks will also need to be fully cured at 150 (or above) degrees, which is drying them to the correct temperature and length of time (typically 60 seconds), in order for the ink to not come off in the wash. A flash dryer will dry and cure the inks in 60 seconds and for longer print runs or larger set ups, a tunnel dryer is recommended.

Drying Options

Iron, Hot Air Gun, Flash Dryer, Hand Curer, Heat press, Tunnel Dryer,

Unsuitable methods
Sun or outside clothes line – Can not be used as temperature is not hot enough.
Household clothes dryer – Can not be used as temperature is not hot enough.
Hand held hair drier – Can not be used as temperature is not hot enough.
Commercial Dryer (Laundromat) – Not a recommended method as temperature is not accurate and time limit can vary greatly on garment type. Garments left in too long may shrink or be damaged.

Comparing Curing Technologies

Curing Technologies

Tunnel Dryers


We manufacture the most comprehensive range of tunnel dryers in Europe ranging from the brilliant ‘Mini dryer’ to the top of the range dryers. The Mini Tunnel Dryer is ideal for the smaller workshop using a tabletop or small standalone carousel up to the top of the range WPS Panther Dryers which are ideal for screen printers with automatic presses or digital printers.

 

Choosing a tunnel dryer

Choosing a tunnel dryer

Panther Tunnel Dryer Comparison Chart

Panther Tunnel Dryer Comparison Chart

More about Exposure Timings

Have you got problems with poorly exposed screens?

Do you have pinholes, stencil breakdown, or poor quality prints?

Are you wasting production time and materials?

Also see our blog post Creating a screen using traditional exposure methods

Following our post last week about exposure timings taken from our FAQs we were asked for more details. Transfering your artwork onto a screen is the most complicated part of the screen printing process, do it incorrectly and you will create problems for yourself. Here we have an example of a design with pin holes.

Design

The principle of the screen is that there is a mesh with little holes. The ink is forced through the little holes on to the substrate (t-shirt, paper, cap) underneath. We only want the ink to go through in certain places, in this case the red lettering. So we create a stencil where our design is black and the background clear and we use red ink. We put emulsion on the screen and expose the screen using the stencil. The emulsion hardens and blocks the little holes in the mesh where it reacts to the UV light. The stencil blocks the UV light in the areas of the design. If the exposure is not correct we can end up with some of the little holes not blocked at all (pinholes) or not to a correct depth or hardness. Then when the squeegee comes along and scrapes the ink along the screen, as well as forcing the ink through the mesh it also scrapes of a little bit of emulsion and makes more holes. This picture shows some pinholes just above the e.

So correct exposure is the key to getting a completely covered, really hard, good quality screen that will last for a long print run.

Most exposure lights and chemicals give you recommended exposure times but these can require fine tuning. The UV light has to harden the emulsion on BOTH sides of the screen. It is a chemical reaction between the emulsion and the UV light that hardens the emulsion. Where the emulsion is hardened the mesh is blocked. The stencil protects the emulsion from the light so when the screen is washed that part of the stencil allows the ink through the mesh.

If your screen is under exposed there is not enough emulsion is on the screen. Then as the squeegee rubs on the screen it removes the emulsion leading to problems.

In this example above the stencil is the red lettering. Therefore the clear area of the screen must be complete blocked by hardened emulsion. But we have some pinholes which means stencil filler or tape are required to block them. Correct exposure will stop this occurring.

Lamps age and whilst it might look like they are doing their job they are not producing enough UV to properly expose the screen

Most manufactures give timings for your lamp/emulsion but it is worth doing a step test at 2-3 month intervals to check for any degradation and so you can fine tune your exposure times.

A step test is a graduated exposure of your screen to see which time has the best results

You can get a step wedge or a Step Transmission Gray Scale,, but you don’t really need one. You can use a piece of thick cardboard to test exposure time. Start by burning the whole screen 1 minute less than the recommended time for your unit/emulsion. Then cover about an inch of the emulsion with the cardboard. Every 30 seconds, cover another inch of the emulsion by sliding the cardboard forward. Once the screen was fully covered by the cardboard, the test is complete. Wash out the screen to find which exposure time produced the cleanest result. Keep a record of this and then you can compare results in 2-3 months time.

A simple inexpensive unit like the WPS exposure unit has all the features you need.

Light Source: 1000 watt halogen light.  More efficient than two x 500 watt light units, where the light can overlap and cause uneven exposure.

Adjustable Height: For adjusting the exposure unit

For 12″ x 16″ screens – 10 inches and expose for 6 minutes

For 20″ x 24″ screens – 20 inches and expose for 15 minutes

For 31″ x 24″ screens – 23 inches and expose for 20 minutes

Important: Foam is charcoal in colour to absorb the light and not to reflect the light as lighter colours will do. This will prevent sharp toothing on fine line work and text when exposing.

You will need to supply your own sheet of glass. The glass needs to be at least 6mm thick double glazed or 10mm thick either single/double glazed.  The thicker the sheet of glass, the more heat from the lamp it will be able to withstand so you can reduce the distance of the lamp from the screen to reduce your exposure time.

This unit will do the same job as a unit costing £500.00+ it just takes a little longer to expose the larger screen.

For the professional printer requiring larger volumes the Heavy Duty Exposure Unit is more sutable.WPS sells a  range of  heavy duty exposure units manufacturer in the UK which come in three standard sizes and a number of variations to suit customer requirements. The three standard models have all the same features, powerful suction pump, touch up lights, safety switch etc. There are a number of power options available 1, 2, 3, 5 & 6 K/w versions.

Two controller options are available, a timer system which comprises a digital timer, and switch for the vacuum and fluorescent tubes as well as a power switch, or our Magellis PLC control system this incorporates an LCD display, time settings and all programable features are accessed from the screen. This unit can also incorporate a light integrator which compensates for lamp degradation over time and automatically adjusts the length of the exposure.

Each unit is fitted with fluorescent tubes for artwork positioning and stencil touch up. The powerful suction pump ensures intimate contact between artwork and screen giving perfect exposures every time.

Each exposure unit is suitable for direct or indirect films and can be used in an open work room.

Screen Printing Tutorials

Screen Printing Tutorials

Whether you are new to screen printing or looking to learn a new screen printing technique we have a great range of video tutorials on our You Tube channel.

From beginners guides like……………….

Dummies Guide to Screen Printing

We talk to a lot of people who want to start screen printing but are not quite sure of the process and what’s really involved. So we thought we would put together a quick video to give you a little.

How to print t shirts or any other garment

Screen printing tutorial by the guys at Wicked Printing Stuff. A step by step guide showing you how to print a logo on a T Shirt.

Advance Screen Printing techniques……………….

How to screen print using a vacuum board

A brief video clip showing a demo of the Wicked Printing Stuff Vacuum Board. Ideal if you want to screen print on paper card or other substr…

WPS Handbench Live Print

Live Printing Event at Fedrigoni with Anthony Burrill, Clerkenwell House using a WPS Handbench and waterbased inks, with Macroy and Jim from P…

Demonstrating 4 Colour Process Print and Screen Printing 4 Colour

Demonstrating a 4 Colour Process Print using Union Inks and Wicked Printing Stuff 6 Colour 6 Station Carousel.

Multi Colour Printing using WPS Waterbased Inks

Video taken during one of our training courses showing a multi colour print using our waterbased ink range

To Product Videos……………….

New Screen Printing Products

Pete Buffham, Director of Wicked Printing Stuff, talking about the launch of new products, especially Panther Tunnel Dryers, WEISS carousels

How WPS Panther Tunnel Dryers are made

A quick promo video to show how we make the WPS Panther Range of Tunnel Dryers at Wicked Printing Stuff. Our range of tunnel dryers are great for small screen printers curing plastisol ink through…

Simple fun squeegee video

We at http://www.wickedprintingstuff.com put together a simple fun little promo video of our squeegee range, but seriously choosing the right squeegee makes a real difference to the quality of you…

Wicked Printing Tunnel Dryers

A fun video introduction our amazing range of tunnel dryers made by us in the UK great for curing Screen Printing Inks such as Plastisol, Waterbased, Discharge and other specialist inks. Our range…

Introducing the Riso QS200 Digital Screen Maker

Looking to get from artwork to print in under 5 minutes, wanting to to ditch messy emulsions. Fed up with printing expensive positives, pinholes, washing out, drying, screen filling, blocking tape…

Screen Printing Supplies

A quick promotional video covering the products and services at Wicked Printing Stuff, we also sell Heat Presses and manufacture the fantastic range of Panther Tunnel Dryers suitable for manual, a…