Comparing Screen Printing Ink Curing Technology

Which curing technology is best for me?

There is often much debate in Screen Printing circles on the best ink curing technology to choose.   Different inks have different ink curing profiles e.g. Plastisol ink 150 – 160 degrees C for 30 seconds,   Water based inks 165 degrees C for 120 seconds –   always check the ink curing profile as there is much variation.  So we are about to  have a go at comparing the technology options.

WPS Essential Tunnel Dryer Live Printing

If you don’t cure the ink properly the ink will crack, fade or in some circumstances disappear after the garments have been thru the washing machine a few times  Always remember to test that the ink is cured. So worth making the right choice.

 

Some water based inks have curing additives (often known as Crosslinkers)  which you add to the ink prior to printing.    Crosslinkers range from additives which allow for a full air dry cure (not heat needed) or those which require the use of heat.  Crosslinkers provide Screen Printers with small tunnel dryers the ability to use and increase printing production when using water based ink.

 

The following ink ranges have Crosslinkers available :-

 

What are the Options?

Hair Dryers – They do not reach curing temperature for either Plastisol or Water based ink.  Very inexpensive. They can be used to dry Water based ink and cure with a Crosslinkers – NOT RECOMMENDED

Do not use a Hair Dryer to cure Screen Printing Ink
Do not use to cure Screen Printing Ink

Iron – The heat is  inconsistent.  Potentially can be use for Hobbyist applications e.g. printing your own T Shirt. Very inexpensive. Not suitable for commercial work – NOT RECOMMENDED

Do not use an Iron to cure Screen Printing Ink
Not Recommended

Hot Air Gun – Can be used for simple Flash Drying (also known as Spot Drying). It is possible to use  to cure Plastisol inks but you need to be very patient especially on large designs. Inexpensive.   – NOT RECOMMENDED for Curing

hot air gun bring used to touch dry ink

Flash Dryer – Often new Screen Printers use Flash Dryers to both ‘Flash Dry’ the ink when printing multi colour designs and for curing ink.  You will need to manage this process very carefully to make sure you do not scotch  garments.  Easier to achieve a full cure with Plastisol Ink then Water based ink.

They range from relatively inexpensive to a significant investment  Professional units. Just be aware that the cheaper Flash Dryers use a lot of power and can be expensive to run – OCCASIONAL USE

WPS Flash Dryer

Hand Curer –  The Hand Curer is a unique device which use Quartz technology often found in Professional Flash Dryers.  It is designed for space constrained environments with rapid cool down.  Good for small studios, home printers and for use in Live Screen Printing Events.  Can be expensive, however cost effective to run.

You can use the Hand Curer for ink curing, however production will be slow.  They are very energy efficient  – OCCASIONAL USE

hand curer for flash drying screen printing ink

Heat Press – Primarily designed for heat transfer applications e.g. Cut Viny media, Sublimation, DTG, DTF etc. Heat presses Can be expensive especially for Professional units. Avoid the cheaper units on eBay. A Heat Press cannot be used as a Flash Dryer but can successfully be used for ink curing. GOOD for LOW PRODUCTION 

Curing Garments with a Heat Press

Tunnel Dryers – Sometimes known as T Shirt Dryers or Conveyor Dryers.  They can’t be used for Flash Drying. Prime purpose is for Ink Curing so perfect for Production work.  There are lots of different types of Tunnel Dryers available, typically the length of the dryer indicates the level of production available.

For small Tunnel Dryers curing Water based inks (typically 2 metres long or less) need the garments to be put through two or three times to achieve a full cure.  We produce a wide range of highly efficient tunnel dryers to suit the needs of the smallest to the biggest screen printers. HIGHLY RECOMMENDED.

Panther 700LW Dryer
WPS Texitunnel 700LW Tunnel Dryer

 

Please note that I ignored the options for using Kitchen Ovens and Tumble Dryers for curing inks,  occasionally this is mentioned in different sources.  Highly recommend that you ignore them as well!

 

 

 

 

Can I cure Screen Printing Inks with a Heat Press?

Can I cure Screen Printing Inks with a Heat Press?

The Simple answer is ‘Yes’,  so before you start set the heat press so that there is almost no pressure. The heat plate should not be touching the print (or it gets very messy!).   Place some grease proof paper or transfer paper over the print before you cure.  Touch dry the ink before curing using a flash dryer or hot air gun.

Do I need a particular brand or type of Heat Press?  – Generally speaking no, we sell the Stahls range which do the job reliably well.  You can use a Clam or Swing Type Heat Press.  We would suggest that you avoid some of the cheap eBay Heat Presses.  They can be unreliable and have inconsistent heat on the platen.

You will need to set the time accordingly,  for Plastisol 45 – 80 secs and Water based inks 120 – 140 secs. Set the temperature  on the heat press slightly hotter than curing temperature.  Like always test before going into a production run.

Occasionally we are asked if you can use a Heat Press to cure Discharge Inks and use special effects e.g. puffer.  Again the simple answer is ‘Yes’ ,  when using puffer ink you will need to adjust the pressure to ensure the ink can rise.  Like always test before a production run.

Long term you are always best to use a Tunnel Dryer for curing to achieve the highest levels of through put.  Heat Presses are good to use in an emergency or in a class room environment but inefficient for production work.

We highly recommend that you flash or touch dry the ink prior to curing.

Can I cure screen printing ink with a Heat Press
Using a Clam Heat Press to cure Screen Printing Ink

Choosing a DTF printer?

Choosing a DTF printer?  – DTF (Direct to Film) has rapidly become a leading garment decoration technology.

The concept has been around for a few years but has gained significant traction,  quite simply it uses inkjet technology to print directly to a film, you  apply an adhesive powder, then cure the film with heat.  You now have a transfer which you can heat press directly onto a garment.

 

How does DTF compare to other garment decoration technologies?

DTG – You do not need to pre-treat dark garments when using DTG printers.  This in itself is a huge benefit.  With DTG you have to dry the pre-treatment prior to printing and have to cure the printer garments for good washability.

 

Typically the curing process takes 120 secs or more, involves lots of energy, time and equipment. For DTF you just need Heat Press for final application of the transfer.  Similar to DTF it uses Water based process inks and white ink to create the print.

 

The best aspect of DTF is that it reduces the need of having boxes of expensive garments on the shelf.  You can apply the transfers at a later date so improving your businesses working capital.

Some DTG vendors are offering DTF as an optional extra.

 

Cut Media – If you are using Cut Media then you are used to weeding.  DTF transfers are printed on either Cold or Hot Peel Film and no weeding is required.   DTF like DTG does not have all of the same options as cut media e.g. foils, metallics colours, fluorescents etc but or the vast majority of designs DTF will do the job so not a complete replacement.

 

Laser Transfer – Laser printed transfers typically have poor washability, lack of versatility and getting the white to work properly can sometimes be a challenge.  DTF printers have white ink so you are able to print complex designs with white ink, easily and effectively. Direct to Film technology effectively replaces the need for white toner Laser printers.

 

DTF is more versatile, better washability and cheaper to produce than Laser Transfer.

 

Screen Printing – For multi-coloured work screen print is time consuming, sometimes messy, involves lots of equipment and experience.  DTF is relatively clean, exact and easy to produce and generally for some designs ideal for low volume work.

 

Screen Printing is a very versatile technology and the range of inks and techniques are unlikely to be ever replaced by DTF.  Screen Printing is still the most economic and cost effective for high volume work.

 

In reality most garment decorators use different technologies, e.g.  both DTF and Screen Printing which gives the best solution for high and low production work.  DTG will gradually be replaced by DTF, Laser Transfers and Cut Media will become more niche.  However like all technologies it is not a Silver Bullet! (even if manufacturers say that it is!).

 

Which DTF printer to choose?

 

It is a busy marketplace there are many Chinese manufacturers which are rebadged by many different vendors. There are DTF printer conversions which you can find on eBay.  There are a range of Powder Shaker / Dryers available to work with the printers.

 

The Shaker applies the adhesive powder to the transfer, it also cures the transfer within the same unit.  You can do these steps manually, and in some circumstances that might be the best option.

When using a Shaker you do need to take into account that you will lose the first 2 metres (or more) of your roll of film as you need to pre feed the film thru the shaker.  There are some solutions and ideas to get around this.

Unless you are a inkjet printer guru and technician we would recommend avoiding home made Epson printer conversions and opt for units designed for DTF.  Why?  functionality such as White ink circulation, maintenance and waste ink management are part of the unit.  Also software for home made units can be variable in quality and you might have to create your own colour profiles.  DTF using inkjet technology, you will become familiar with printhead maintenance very quickly.

 

The home made conversions don’t have this,  the initial purchase price maybe cheaper but you will spent a lot of time repairing and maintaining your printer.  Time is money, you will spend a lot of time on forums / social media trying to find maintenance solutions.

DTF Direct To Film Printer

If you purchase a smaller printer you will need someway of curing the transfer sheets.  You can use a DTF oven or a Tunnel Dyer – the WPS Premium Tunnel is perfect for this as it can run off a 13amp plug.  It is significantly faster than using a DTF oven.

DTF oven

WPS Premium Tunnel Dryer perfect for DTF and Screen Printers

The larger wide format printers are normally used with an inline Shaker / Dryer unit.  We recommend the  DTF Printer SD-70 – it is quick, well made, comes with a usable RIP (good software is essential), small footprint vertical Shaker unit.  More importantly it comes with support and maintenance services to keep your business running.

DTF printer with shaker

Use Quality consumables

it is easy to buy cheap consumables from eBay and then pay for it with maintenance or quality issues.  In particular choosing the right powder is important there are general purpose powders and some designed to be more effective for dark garments and sports wear. The SD-70 has a range of consumables and inks which are certified and designed for the unit.

 

For Audley, Oric etc and WPS DTF A3 printer and home made conversions we recommend the Indie ink range of PET Film, DTF Inks and Powder.  The vast majority of DTF printers use Epson print heads so there is a degree of compatibility.

 

As always if you need help then give us a call on 01614426555 or email sales@inkandsolvents.co.uk

Choosing a Screen Printing Exposure Unit?

Choosing a Screen Printing Exposure Unit?

We are often asked “what is the best exposure unit for my screen printing business?”

Like always what seems a simple question does not have a simple answer. So we thought we would put this guide together to help work through your requirements and to come up with the right answer for you.

Let us first look at what YOU need for YOUR Screen Printing business. Think about these considerations and questions?

  • How many screens do you plan to produce on a daily basis (a couple here and there or up to hundreds per day)
  • What is the maximum screen size you use?
  • Do you have any space limitations?
  • Are you a hobbyist printer, commercial or educator?
  • What is the size of your budget?
  • What kind of artwork are you producing? E.g. Complex design with very detailed half tones / 4 Colour Process CMYK or typical T Shirt artwork (medium resolution / block style artwork)
  • We are going to do our best to avoid baffling techy jargon

Now let us look at the Exposure Unit solutions from simple to heavy duty.

WPS LED Exposure Lamp

LED exposure lamp on stand

WPS LED Exposure Lamp is a simple solution,  which are used every day. Good for hobbyists / home printers who make a handful of screens per day. Comes as part of our Screen Printing Kit range.

Pro: Very Cost Effective, can create excellent stencils and you can expose large screens. Note that the lamp does not have a vacuum therefore you need to ensure that the positive is tight and intimate with the screen. To do this you use sheet of glass (the heavier the better) which ensures that the film positive and screen are very tight.

This Exposure Unit uses LED which are powerful and reliable. They are very energy efficient and do not generate heat.

Cons: Can be slow (5 – 20 minutes depending on screen size) depending on the screen printing emulsions, requires space (large cupboards are ideal), the printer has to time the stencil exposure – there is nothing ‘hi tech’ about the lamp solution but it works.

WPS Mini Exposure Unit

WPS Mini Essential Exposure Unit showing the Actinic Tubes

 

The WPS Mini Exposure Unit uses proven “Actinic” tubes in a tight array. This exposure unit comes with a yellow pilot light which you use to position the film positive with the screen. The unit comes with an integrated timer (you can set multiple programs) and vacuum which is extremely easy to use.

We have used these units for a number of years and have been pleasantly surprised at the quality of stencil produced even with very difficult artwork. Typical exposure times from 120 – 300 seconds depending on what kind of emulsion and the number of coats you are using.

Drying Cabinet Ideal for small print shops, schools and colleges –  You can also purchase the unit with a drying cabinet which really does improve production with a relatively small footprint.

WPS Exposure Unit with drying cabinet

Pros: Very easy to use, very tight vacuum, and uses proven technology giving high quality stencils. Different sizes of exposure unit available to accommodate different frame sizes.

Cons: Not many, if you are a creating lots of screens you will have to replace tubes at some point.  Traditionally there has been debate that  tube units do not produce stencils as sharp as from a single light source. With tube units, light comes from multiple angles, potentially undercutting the positive during exposure which can result in the loss of fine detail. However our units have a dense tube array  we have not experienced many issues at all with this kind of unit.

These units can be used in a high production environment e.g. 50 – 70 screens per days. However do budget to replace the bulbs on a regular basis as they will gradually degrade.  You can always choose the LED version.

WPS LED Mini Exposure Unit

WPS Exposure Unit LED showing LED array

The WPS LED Mini Exposure Unit, consist of UV LED technology positioned in a tight array, similar format to the “Actinic” version. It comes with a yellow pilot light which you use to position the film positive with the screen. The unit comes with an integrated timer (you can set multiple programs) and vacuum which is extremely easy to use.

LED technology has started to make inroads into the screen printing industry, so the technology is relatively new and is continuing to be developed. Like the standard unit it also available with a built in drying cabinet which is great for increasing production and reducing mess.

Pros: Very quick (15 – 300 seconds depending on emulsion / number of coats etc.). Very easy to use, very tight vacuum, LED technology using low power, does not generate heat. LEDs are long lasting (stated to be very long life) and produce high quality stencils. Different sizes of exposure unit available to accommodate different frame sizes.

Cons: Initial purchase price higher than Actinic units. The LED array emits light from multiple angles undercutting the positive during exposure which can result in the loss of fine detail. However with LED technology this seems less of a problem than tube units and is commonly not considered a problem for the vast numbers of printers (99.9%).

LED technology is new and is continuing be developed.  The LED are to be manufactured to emit the correct light frequency, you can’t use generic LEDs for exposing screens.

Ideal for small / mid, large screen printing shops and educational establishments who need to produce lots of screens quickly. These units are designed for high production environments. There are also version available for printers who have invested in direct to screen technology.

 

WPS Heavy Duty Exposure Unit

Metal Hallide Exposure Unit

The Heavy Duty Unit uses a  Metal Halide bulb, they come in lots of different configurations.  Including different bulb ratings and features such as integrators.  An Integrator measures the quantity of light reaching the screen and adjusts the exposure if there are any voltage fluctuations or to compensate for deteriorating bulbs.  Some units have rapid start-up, it can take time for a metal halide bulb to get to the correct operating temperature. These units are fast and give very accurate stencils.

Metal Halide is still probably the most popular light source used for mid and large screen printers.  Some Heavy Duty Units use a Halogen bulb.  This type of bulb are rapidly going out of production.

Pros: Very fast (depending on the power options you choose). They come with advanced features so you can produce large numbers of stencils quickly, consistently and accurately. Often used in heavy industry environments and for used for multi applications e.g. exposing print plates. Different sizes of exposure unit available to accommodate different frame sizes.

Cons: Metal Halide bulbs are expensive (£200 – £400 common prices).  They generate heat and consume much more energy than LED units (LED exposure units typically use 1/5 of the energy of a metal halide unit). Many screen printers are moving over to LED technology.

 

In summary

When choosing an exposure unit take some time and think about your current and future screen printing requirements. There are lots of exposure units to choose from all giving different levels of production capability and quality.

The exposure units with combined drying cabinets are very cost effective and increase productivity. If you are looking to replace an older unit e.g. metal halide unit.  We would highly recommend that you consider LED units.

Please feel free to contact us to discuss your requirements. We can help you to find the right exposure solution for your needs. sales@inkandsolvents.co.uk

 

Screen Emulsions Explained

Choosing a Screen Printing Emulsion

Choosing the right screen printing emulsion (also known as photosensitive emulsion) is a little like buying a car, they all effectively do the same thing but have different features, methods of use and performance factors which differentiates them.

All of the emulsions react to UV light causing the emulsion to cure and harden. If you are new to screen printing check out our tutorial on YouTube which covers the basics and shows you how to create a stencil using photosensitive emulsion.

There are three main groups of emulsions on the market:-

  • Diazo – been in use for many years, the emulsion needs to be sensitised before use. They come with the sensitiser is a separate pot or sachet.
  • Photopolymer, sometimes referred to as SBQ Photopolymer (Styryl Basolium Quaternary). The manufacturers mix in the sensitiser with a polyvinyl base meaning that the emulsion is ready to use and you don’t have to mix in a sensitiser. Commonly known as ‘One Pot’ emulsions.
  • Dual Cure – a combination of both types of emulsion but mostly (there are some exceptions) need to be sensitised before use. Dual Cure emulsions are the most popular as they incorporate the strengths and weaknesses of Diazo and Photopolymer emulsions.

Autosol 6000  Diazo Emulsion (Authors favourite when using waterbased inks)

 

Diazo Emulsion – Pro Con
They have a wide exposure latitude (so very forgiving if you have not got your exposure timings spot on) 

 

Cost effective and reliable

 

Can be formulated to be water resistant or solvent resistant e.g. if you use waterbased inks you need a water resistant emulsion and if you use plastisol and solvent inks you need a solvent resistant emulsion

 

We sell Autosol 6000 and Sericol Dirasol 25

Less light sensitive than the other emulsions so if you light source (exposure unit / lamp etc) is not stronger you could be exposing for a while! 

 

Not so good for fine detail and halftones (often subject to much debate) , Diazo emulsions are normally quite thick but this is not always the case with all of the Diazo emulsions on the market.

 

More difficult to reclaim than the other emulsions especially the water resistant variants.

Chromaline CTR Photopolymer Direct Emulsion

Chromoline CTC

 

Photopolymer Emulsions – Pro Con
One Pot – you don’t have to mix in with Sensitiser powder which is unpleasant stuff and is fraught with health and safety issues. 

 

Good for high production print shops

 

Easy for reclaiming the screen

 

Can be formulated to be water resistant or solvent resistant e.g. if you use waterbased inks you need a water resistant emulsion and if you use plastisol and solvent inks you need a solvent resistant emulsion

 

We sell Chromaline, Ulano, Sericol and Macdermid ranges of Photopolymer emulsons

Very light sensitive – you also need a strong reliable light source e.g. Metal Halide / LED and in some circumstances Actinic / Tube units. 

 

Your exposure timings have to be spot on.

 

Typically the most expensive emulsion

 

Autosol 5000 – Very Popular Universal Dual Cure Emulsion

Autosol 5000 screen printing emulsion
Autosol 5000 dual cure emulsion a great general purpose emulsion suitable for plastisol and waterbased screen printers

 

Diazo Emulsion – Dual Cure Con
 

They are relatively quick to expose and work with most light sources

 

They have a wide exposure latitude (so very forgiving if you have not got your exposure timings spot on)

 

Cost effective and reliable

 

Good for fine detail and half tones

 

Easier to reclaim the screen compared to Diazo emulsions

 

Can be formulated to be water resistant or solvent resistant e.g. if you use waterbased inks you need a water resistant emulsion and if you use plastisol and solvent inks you need a solvent resistant emulsion

 

We sell Ulano Proclaim, Macdermid Autosol and a wide range of Sericol and Chromaline emulsions

 

Shelf life is not so good as Photopolymers

 

 

Most Dual Cure emulsion need to be sensitised, but one pot solutions are now on the market such as Ulano EC

 

Ulano ECUlano EC one of the first ‘one pot’ Dual Cure emulsions on the market, also has 18 months shelf life. No need to add sensitiser – ready to use straight from the pot.

 

 

 

 

Tips

  • Choose the emulsion which gives the right stencil resistance e.g. if you are using Plastisol then choose an emulsions which gives a solvent resistant stencil and water resistant if using waterbased inks. Otherwise you will find your stencil starting to break down.
  • Some dual cure emulsions can be used with both water based and Plastisol inks. However if you are using the same emulsion we recommend that you ‘double bake’ . This increases the exposer the screen again after it has initially dried to strengthen the stencil.
  • If you are using wate rbased discharge inks for large scale production.  We recommend emulsion which is  designed for discharge inks such as MagnaPrint.
  • Keep the emulsions in the fridge (but don’t freeze) it will extend the usable life
  • If you use sensitiser powder emulsions always follow the instructions. Mix the powder in well and leave for a couple of hours to let the air out the emulsion before use
  • If you don’t have a strong light source, don’t want the hassle of sensitiser powder. Ideal if you don’t expose many screens then try out a one pot dual cure such as Ulano EC it is rather good

What is a discharge ink?

I want the print to have a soft touch?

What is a discharge ink?

Here at Wicked Printing Stuff we don’t expect you to know everything and we are happy to explain things.

So you want to print a light colour on a dark garment and you want it to feel soft. Now plastisol inks wrap colour AROUND the threads but gives a rubbery feel (also referred to as hand) but is bright. So ideally you want a water based ink. For those of you that have tried this and I can hear you shouting at the back, but I have tried water based inks and I just can’t get a good opaque print, that’s why I use plastisol. Well that’s where the discharge inks come in! Printed using MagnaPrint AW Discharge Inks

For the punk rockers out there, remember how you got that bright green hair, that is right you had to bleach out your own hair colour first so the back ground colour was white, only then the colour would take and be vibrant and striking. It is almost the same in screen printing but we use discharge inks that need curing. The discharge ink actually removes the dye.

 

First off you have to have the right garment fabric, it has to be 100% cotton and it has to be dyed with a dischargeable dye. So check with the manufacturer. If the garment is a mixture of cotton and polyester only the cotton will discharge. Now that might actually suit you but you would need to do a trial run to make sure you get the effect you want.

 

Discharge Inks

So having got the right garment now we need the right ink. There are a lot out there and some are more complicated to use than others.

Water based dischargeable inks are the easiest and most eco friendly ones to use. The process works during curing when the discharge removes the original dye and the ink gives the new colour. To do this you add activator to the ink which ensures you get an intense colour.

 

At Wicked Printing Stuff we have researched the products extensively.  As a consequence we have developed our own range  the splendid WPS Premium Discharge Ink.   The ink is based on MagnaPrint AW .  Which has been developed to meet the most recent ecological requirements.

 

For the discharge process to work, you do need a tunnel dryer (the longer the better).  Typically 90-120 seconds dwell time is needed for a good cure. You can also use a heat press which is great for low production. You also need well ventilated premises and printers should read the MSDS and be aware of any health and safety consideration.

Tips for great Film Positives

A decent film positive is an essential part of achieving a great stencil as part of the exposure process.  A simple test is to hold your film positives up to the light.  If the light can be seen through the artwork then the positive is not dark enough.  We do not want the light getting through the artwork when exposing.

Good time to take a look at our exposure issues guide.

So some tips…

Double up on your film – print out 2 copies then cut the corners off one of the films, line them up and stick together with invisible tape. Make sure that the film positive is nice and tight against the screen.  Especially if using a lamp system and does not have a vacuum.  Some purists will be frowning at this solution, but it works!

Use decent film positive paper, inkjet film is coated to ensure that ink completely adheres to the paper which in turn makes the artwork darker.

Get yourself an Epson – they seem to be the best at putting down more black than many other brands. The Epson printers are rather good recommended models – 1500W (if you can find one) and the Epson ET14000 – use the blacquer ink system which is designed purely for making film positives – it’s very cost effective and does the job. The ET14000 using bulk ink tanks rather than cartridges – Key Tip is to use the printer on a regular basis ideally every workday to reduce ink drying issues.

Blacquer Epson ET14000

 

 

If you are using a laser printer then buy an Epson (sorry showing a bit of a personal preference there).  There are some Canon printers are apparently good for Film Positives. Seriously if you are using a laser then you can use a toner density spray which makes the artwork darker. The old technique was to paint oil (vegetable most popular or white spirit) over the artwork – but rather unpleasant!

Toner Density

 

Exposure Troubleshooting Guide

Having issues exposing screens?  Then take a look at our Exposure Troubleshooting Guide.

Making Your Artwork Positive.
Making Your Artwork Positive.

Having problems getting the right exposure times?

Stencil not washing out?

Stencil too easily losing definition?

Experiencing stencil breakdown whilst printing?

There can be lots of reasons for these problems so we have compiled a simple troubleshooting guide which might help you. It won’t solve every problem but hopefully will point you in the right direction.

Problem Possible reason and remedy
Image will not washout Are you using the right level of water pressure? You can use a power hose using light to medium pressure. Normal tap pressure is not enough. If using a pressure washer, is set it to its lowest setting?

How opaque is the film positive? Hold it up to the light. If it is letting light pass through then the emulsion will start to harden making washout difficult. Make sure your film positive printer is set to the darkest settings, you can print out 2 copies of the film positive and stick them together.   You can also use a density spray if printing Film Positives on a laser printer.

Has the emulsion gone past its shelf life? Write the date on the label when sensitising – it may save a lot of time and frustration.

Screen maybe over exposed. Check your exposure timings – you can use an exposure calculator to determine the right timings / settings for your exposure unit

Make sure when drying the screen after coating that you don’t overheat it. Temperature needs to be kept below 40c.

Not all of the image washes out or washes out easily Screen likely to be under exposed other tell-tale signs include:

If the water runoff is heavily emulsion coloured when washing out and if the emulsion feels slippery and soft.

·         Check your exposure timings – you can use an exposure calculator to determine the right timings / settings for your exposure unit

Check for uneven contact between the positive film and screen when exposing. Check the vacuum is working correctly / or glass & weights are in place.

Could be uneven coating of emulsion on the screen. Check the tension of the screen – if it is loose you will not get an even coating of emulsion. Maybe time to get the screen re-stretched.

Only use light to medium water pressure – too much pressure can remove the artwork inadvertently, resist the temptation to give the artwork a blast with the power washer on anything but light setting. After initially wetting the screen on both sides, washout from the print side only with just a final rinse on the squeegee side.

Make sure that the emulsion has been sensitised correctly, the sensitizer powder must be completely dissolved – maybe consider a pre-sensitized emulsion such as Ulano Proclaim EC.

Always degrease the screen before coating with emulsion it helps the emulsion adhere to the mesh as well reducing the chance of pinholes and fish eyes

Stencil washed out but ink won’t go through part of it when printing Check your exposure timings as the screen is likely to be underexposed – you can use an exposure calculator to determine the right timings / settings for your exposure unit

Make sure that the emulsion is thoroughly washed out as the emulsion can run into the stencil on the squeegee side blocking the artwork. Sometimes you can clean it out with a damp cloth (luck is involved – so best to get the exposure timing and washout right)

Stencil not dried properly after washing out – you can’t beat a drying cabinet (either manufacturer or homemade). Always inspect the stencil in the light to make sure no moisture remains.

Before exposing make sure that the screen is completely dry, the emulsion should be the same ambient temperature of the drying room. If the emulsion is cooler it still has some water content.

 

Fish Eyes Normally caused by contamination so make sure you have degreased your screen thoroughly and that your workspace is clean. Also check that the exposure unit glass is clean and that there is no contamination on the film positive.

Check that the coating trough is clean, dust free and that the edge is completely clean (make sure there is no evidence of the old emulsion on the coating trough).

When coating the screen, move the trough steadily and with purpose. If you coat too fast the emulsion won’t adhere to the screen correctly. Conversely if you coat too slow and the coating may be too thick.

Fish Eyes can also occur during printing if there is an issue with the emulsion e.g. over its shelf life

Pinholes Similar to Fish Eyes – watch out for contamination on the mesh so make sure you degrease screens.

Dirty glass on the exposure unit is often a culprit, or contaminated film positives.

Make sure that there are no air bubbles in the emulsion when coating – when sensitizing emulsion leave it at least for a couple of hours (ideally leave overnight) before using it to allow the air to escape.

Don’t coat too fast – allow the emulsion to adhere and fill the mesh aperture

 

 

Top Tip – Useful tools

Chromaline Exposure Calculator

Image result for Chromaline Exposure Calculator

Chromaline exposure calculator eliminates miscalculated exposure time with three kinds of quality checks. An easy, user friendly tool for the novice and the advanced screen maker.

Designed to help determine correct exposure time, print quality check and halftone tests.

https://www.wickedprintingstuff.com/exposing_equipment_and_digital_screen_makers/accessories_inc_bulbs_foam_and_exposure_calculator_LC241/chromaline_exposure_calculator_P2548.html

 

Maybe the best investment you make!

Simple Guide to screen printing Plastisol Transfers

Simple Guide to screen printing Plastisol Transfers

Plastisol Transfer are a great way to make your screen printing business more flexible and reactive to customer need especially when you receive repeat orders of the same design. Instead of printing direct to the garment, you print onto a transfer paper which can be heat pressed onto the garment at a later date.

How do you make a single colour transfer?

Prepare your screen, coat the print side (side closest to the garment) 3 times and squeegee side at least once with emulsion (using a dual cure emulsion).  If you are using one of our WPS Essential coating troughs then you can use the thick edge which will give you thick covering of emulsion in one coat.  Remember to fill the trough at least ¾ full – you don’t want to run out of emulsion.

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The artwork needs to be mirror image.  Expose the screen (note – you will need to increase exposure time when adding additional coats of emulsion).  Check our exposure troubleshooting guide.

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Tape up the screen and register on your press as per normal.

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In this article I am printing onto a dark garment  using WPS Premium Cotton White Plastisol Ink.  We recommend that you use the high opacity inks rather than mixing inks.  When printing transfers you need a thicker deposit of ink compared to a direct print.  We are using a squeegee with a 65 durometer blade (soft square cut blade) as we need a good deposit of ink to go through the mesh (using a 43T with white mesh).4

Spray some hi-tak down on the platen, alternatively you can use a vacuum board as the paper needs to be kept firm on the platen.

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Place the transfer paper on the platen and make sure it is firmly positioned.  In this article we are using cold peel transfer paper which gives us a heavier deposit of ink.  You can use hot peel paper (we will discuss the differences in a later article).  You can print on either side of the paper.

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Flood the stencil with ink and print as per normal. One of the reasons of having extra coats of emulsion is to give a thicker stencil.  We don’t want to utilise print / flash / print steps when printing transfers.  We want (and need) as much ink to go through in one print stroke.

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Lift the screen, you will see the printed paper.

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You now need to cover the print with transfer adhesive powder, this ensures that the ink adheres to the garment.  Cover all of the ink with a fine coating of powder.  In this article I have simply poured the powder from the tub – you can use sugar / salt shakers. There are many techniques for manual powder application.   I am often asked about not using a transfer adhesive powder – it is possible to get a good result without the powder but it is rather hit and miss.

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Make sure all of the ink is covered with powder, then put the excess powder back in the pot.  The next step is to touch dry the ink – in this article I have used a heat press setting the heat platen at least 2-3 mm from the ink. The temperature  on the heat press set to 180 degrees C and timed for 10 secs – just enough to tough dry the ink).  If you are producing lots of transfers it is best to use a tunnel dryer. You set the belt speed high, you do not want to cure the ink.

When you have your printed transfer you can file them away (keep dry and avoid humidity) and heat press onto the garment a year or so later.

When you are ready to apply the transfer, place the paper on the garment (print facing down).  I am using a clam heat press but swing away heat presses work just as well.  Set a tight pressure and heat press (180 degrees C for 20 – 30 seconds depending on how good your heat press is. You might have to experiment to get the right results).10

After heat pressing the transfer, rub the back of the transfer with an old T Shirt.  Note – this is more habit on my part but it always seems to work!  After 40 seconds peel off the paper.11

After peeling back the paper you are left with the end product, a very opaque and soft hand print.

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