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!

Try our ‘Art to Screen’ service and never emulsion another screen

I think we would all agree that creating a screen is the most complicated part of the screen printing service. Getting the exposure right, choosing the right emulsion, drying properly, pin holes, under exposure there are so many areas where you can make an error and your screen is useless.

Art to Screen Exposure Service

There are some great machines around that will take artwork from a computer and produce a screen but these are way too expensive for the hobbyist or small printer. So what do you do?

 

Use Wicked Printing Stuff ‘art to screen’ exposure service. That is right you need never emulsion another screen. We do these all the time, designers send us their artwork and we send back the perfect screen(s) so you can get printing straight away.

 

Our Art to Screen ‘screen exposing’ service is for either screens bought from us or those that need to be reclaimed and / or re-stretched. Ideal for people new to printing; do not have access to the equipment or those printers who simply do not have the time. This service means that you never have to turn down a job because of the complexity of exposing your screen. Aluminium frames only.

 

We can provide the following services:

  • Artwork preparation and separation
  • Screen Reclaiming
  • Screen Restretching
  • Screen Exposing – single and multi colour designs

 

In order to do this we need to know a few things like:-

  • How big is the design / logo?
  • How many colours are in your design / logo?
  • Is there anything special about the design (e.g. glow in the dark, glitter)
  • Are the designs already available and colour separated?
  • What will you be printing onto: t-shirts / cotton or paper bags / card etc?
  • Where will it be placed on the substrate? E.g. breast / sleeve / full front / back/ middle of bag etc
  • What ink will you be printing with – plastisol / waterbased / solvent based?
  • What type of carousel / press do you use – does it have micro – reg?
  • How quickly do you need your screen?
  • Are there any other important factors we need to know about?

 

Then think about what service you want from us?

 

  • Artwork Support – separation, stencil preparation
  • Screen Exposure – preparation and make up of screens
    • WPS provide screen and mesh to your choice and expose
    • You provide screen for reclaiming and exposing
    • You provide screen for remeshing and exposing
    • You provide the screen for exposing only
    • We can arrange collection of the screens and delivery back to your address. Alternatively you can arrange for the screens to be delivered to us and collected.

 

We can even clean the screens you provide if wanted.

Details of our ‘Art to Screen’ screen printing exposure service are on our website

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.

More from Riso – the Goccopro 100 Digital Screen Maker

RISO Digital Screen Makers 3

The GOCCOPRO 100 is a digital screen maker that will take single or multi-coloured artwork and digitally turn it  into a stencil ready to attach to your frame for screen printing. It’s ideal if you need rapid turn around times because you no longer need to coat, dry and expose your artwork before printing.  You will not only save time but also money as you can do without emulsions, degreasers, exposure units, drying cabinets and copious amounts of tape.

You create artwork (and separate if multi colour) as normal, send the artwork directly to the GOCCOPRO which then creates the stencil, when completed you take the stencil and attach it to the frame.  You are now ready to register the frame on the press and print.

 

The GOCCOPRO 100 uses a special mesh which is coated with a special heat-sensitive polymer. There are 4 different mesh counts ranging from 32T to 77T so you can use a variety of inks including solvent, Plastisol and water-based. The mesh is not re-usable and when you have finished printing you dispose of it. The GOCCOPRO 100 also uses a type of custom frame so you won’t be able to use your existing frames.

The special frames for the GOCCOPRO come in different thicknesses and sizes and which type you choose will depend on the job and volume you are printing. The maximum print size is 300mm x 800mm. Depending on which frame you choose you will be able to print batches which range from 1 to several thousand prints.

Revolutionary Riso QS200 Designed for the Professional Printer

Looking to get from artwork to print in under 5 minutes

Want to ditch messy emulsions

Fed up with getting exposures wrong

Need super fast turn round for an event, a winners t-shirt before they leave the podium.

 

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Revolutionary Riso QS200 – typical screen burn times range from 2 – 3 minutes. With no need for chemicals / emulsions or exposure equipment but with excellent registration. Works just like a typical printer. Can create screens up to A2 in size.

Get the perfect screen every time.

No more worries about subdued lightening

Works just like a printer

Super cost effective.

Designed for professional commerical printers or for environments where you need a fast turn around of screens. The QS200 creates screens up to A2 in size with extremely accurate registration allowing for multi colour jobs suitable for both manual and automatic presses.RISO Digital Screen Makers 1

It is extremely fast with screens being created within 3 minutes (A4 size artwork 2 minutes), the QS200 connects directly to your PC or MAC and acts as a conventional printer.  You separate your artwork as per normal however instead of printing the film positive. you print directly to the screen. When completed (normally within 3 minutes)  you are ready to register the screen and start printing giving a huge productivity boost.  No need for emulsion, exposure units and of course no pin holes, no screen filling, no stencil breakdown, and no need for screen reclaiming or restretching.

The biggest revolution in screen printing since polymer screens.

With the QS200 you save time, space but also money as you can do without emulsions, degreasers, exposure units, drying cabinets and copious amounts of brown tape. Imagine the savings!
The QS200 uses a special mesh which is coated with a special heat-sensitive polymer. There are 4 different mesh counts ranging from 32T to 90T so you can use a variety of inks including solvent, Plastisol and water-based.

RISO Digital Screen Makers 2You can either use frames which you can stretch yourself (takes approx 5 minutes, but gives a high tensioned screen) or alternatively you can use conventional frames (up to 50mm profile) or Newman roller screens and stretch the polymer film to the required tension. The film is not re-usable and when you have finished printing you can dispose of it.

For full details contact us now!

You will wonder how you ever did without it.

 

 

Screen Printing Exposure Units and Digital Screen Makers

Exposing eq&digital screen M_2

What are your options for the most important part of the screen printing process, creating the the screen itself.

  • This can be done the traditional way by coating the screen with emulsion, exposing the artwork and hardening the exposed emulsion. This does require a certain degree of skill but practise does make perfect.
  • The newer options are equipment such as Digital Screen Makers that creates the screen, an expensive piece of kit but worth it for the busy printer.
  • Lastly we can do it for you with our ‘Art to Screen’ service

Wicked Printing Stuff have a comprehensive screen creation range :-

  • exposure units
  • digital screen makers
  • accessories
  • kits

which are used for transferring your artwork onto your screen. Alternatively try our  ‘Art to Screen’ service where we do all the hard work for you.

We sell a range of ‘all in one’  self contained exposure units suitable for mid to large sized screen printing shops.  The Actinic and WPS Mini Exposure units ideal for educational and medium sized screen printing businesses (typical exposure times 120 – 180 seconds) and the heavy duty units ideal for busy print studios and larger screen printing businesses where large numbers of exposures required per day (typical exposure times 30 – 90 seconds)

 Digital Screen Makers, allowing you to transfer the artwork directly to the screen without the need for emulsion, exposure units, washout equipment and film positives.  Great for increasing productivity and screen turnaround times.

  • Goccopro 100 – Ideal for small printers requiring quick production of screens
  • QS200 – Ideal for professional screen printers with both manual and automatic presses – creates screens up to A2 in size. Click here to see our QS200 promotional video.

For beginners, smaller businesses and home printers we manufacture the Wicked Exposure Unit , very cost effective. Additional foam base sizes can be purchased as extras for other sized screens if you require.  Check out our screen printing tutorial (Step 4 –  7mins 10 seconds if you want to skip to the relevant section)  which shows how you use the Wicked Exposure Unit to transfer your artwork to the screen.

We have put together a number of screen exposing kits that include everything you need to get started at an affordable price.

I think we would all agree that creating a screen is the most complicated and frustrating part of the screen printing process. Getting the exposure right, choosing the right emulsion, drying properly, pin holes, under exposure there are so many areas where you can make an error and your screen is useless.

There are some great machines around that will take artwork from a computer and produce a screen but these are way too expensive for the hobbyist or small printer. So what do you do?

Use the Wicked Printing Stuff ‘art to screen’ exposure service. That is right you need never emulsion another screen. We do these all the time, designers send us their artwork and we send back the perfect screen so you can get printing straight away. So, whether you are new to printing, lack access to the equipment or simply don’t have the time, this service is ideal for you and means that you never have to turn down a job because of the complexity of exposing your screen.

The service can be used on newly purchased or previously used screens that need to be reclaimed and/ or restretched. Read the attached guide that gives you further details.

Do please look at all our blog posts on screen creation by using the tag ‘Creating a screen’

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?

 

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 can I get rid of Pinholes?

How can I get rid of Pinholes?

wicked_potsMake sure you have degreased your screen before you coat with emulsion, if you leave screens around without sealing them it’s surprising how much dust there is.

Make sure the glass on your exposure unit is clean – dust gets every where! If you do find pinholes then you can either cover them up with tape or you use a screen filler which you can apply with a brush to cover the hole.

Make sure you use solvent resistant fillers with plastisol and solvent inks, use water resistant screen filler when using waterbased inks.

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

How long will it take to expose my screen?

How long will it take to expose my screen?

04

Using our 1000watt halogen exposure unit setup, it will take 20 minutes to expose your screen, with the unit set at the minimum distance light to screen. For different exposure units and bulbs types the timings are likely to be different so check with the manufacturers guidelines

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

How important is it to degrease the screen?

How important is it to degrease the screen?

wicked_pots

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.

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