How can I print light designs on a dark garment – All about discharge inks.

I want to print light on dark?

I want 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. Have you checked out our FREE buyers guide there is lots in there for the Rookie, Intermediate and Professional. Please give us a ring and explain your problem and we will help out. Lastly there are our training courses, designed again for both rookie and advanced printers with basic training or advanced courses.

So back to the problem. 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 waterbased 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!

Punk Rockers

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 InksSo 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 and as a consequence we recommend the following ink Unico  The ink has been developed to meet the most recent ecological requirements. We also supply the Rutland Best of Brands discharge ink which works with both the Unico and the Union activator. Additionally we offer Union plasticharge which is a great way of using existing plastisol inks you may have and turning them into a discharge ink.

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.
We would be delighted to talk you through this if you have any questions, please contact us.

What is the best exposure unit for my screen printing business?

Choosing an 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 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 so if this is all new to you we suggest that to take a look ‘Is screen printing for me article’ and our video tutorial which will help you understand the basics.

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

WPS Exposure Lamp

Exposure Lamp

Very simple solution, there are thousands out there, which are used every day. Good for hobbyists / home printers who make a handful of screens per day. Comes as part of our Essential and Mid range screen printing kits.

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 halogen bulbs (1000W) which are powerful and cheap to replace.

Cons: Very Slow (10 – 20 minutes depending on screen size), 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

Mini Exposure Unit

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 140 – 300 seconds depending on what kind of emulsion and the number of coats you are using.

Drying CabinetIdeal 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.

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: Potentially 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 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.

 

WPS LED Mini Exposure Unit

LED Exposure Unit

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 (30 – 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, is long lasting (stated to be very long life) and produces 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.

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. We tend sell this units to printers who have invested in direct to screen technology.

 

WPS Heavy Duty Exposure Unit

Heavy Duty Exposure Unit

The Heavy Duty Unit uses a single point Metal Halide bulb, they come in lots of different configurations with different bulb ratings and features such as integrators (measures the quantity of light reaching the screen and adjusts the exposure if there are any voltage fluctuations or to compensate for deteriorating bulbs) and 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.

Pros: Very fast (depending on the power options you choose) and can 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), 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 then we would highly recommend that you consider LED units.

Please feel free to contact us to discuss your requirements and we can help you to find the right exposure solution for your needs.

 

 

 

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!

Screen printing fundamentals

Starting out and want to know the fundamentals of screen printing?

Ink blocking

Screen printing is a printing technique that uses a woven mesh to support an ink-blocking stencil. The attached stencil forms open areas of mesh that transfer ink or other printable materials which can be pressed through the mesh as a sharp-edged image onto a substrate. A fill blade or squeegee is moved across the screen stencil, forcing or pumping ink into the mesh openings for transfer by capillary action during the squeegee stroke.

 Stencil Printing

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. It is also known as silkscreen, serigraphy, and serigraph printing. You can also have more than one colour printing, for example you could have a striped printing

FAQ Screen Printing – How is the design transferred to the screen?

Wicked_poster_step3

You need to follow the ‘exposing process’.

Firstly you need to make your artwork positive, then coat your screen with emulsion. Once that is done you are ready to expose your artwork onto the screen using an exposure lamp or unit.

We find that this can be the most tricky part of the screen printing process. For more details check out our buyers guide and YouTube videos.

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

Which dryer is suitable for my carousel and inks?

Which dryer is suitable for my business?

It you have an automatic carousel printing water based inks then a small dryer is obviously not suitable but which dryer is the right one. This chart will guide you.

At Wicked Printing Stuff  we manufacture our own Panther dryers and these can be standard models or very client specific. For example a dryer suitable for DTG (Direct to Garment) printing needs a much longer tunnel. Our prices are very competitive because you are buying direct, ask us for a quote and be surprised.

Choosing a dryer

You can watch our dryers being made in this fun video.

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

INKS_BOX

The ink seems too thick.

If your ink is too thick or you are having problems with it passing through your screen, you can thin the ink down always give the ink a good stir first as sometimes that will loosen the ink making easier to print.

However the problem with some inks is that because of the pigment content needed in them to appear opaque on a garment it NEEDS to be thick.

If you are having problems with general Plastisol ink this can be thinned down using curable reducer.

This will not affect the quality or the curability of the ink if you keep with the recommended ratio but gives it a softer hand and makes it easier to pass through a higher mesh count. If too much is mixed in, the ink will become too runny and no longer work.

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

What is the difference between Yellow and White mesh?

What is the difference between Yellow and White mesh?

20140721_105635Generally speaking there is very little difference in the performance of the mesh unless you are using 90T upwards. Yellow mesh absorbs more light and stops light scattering, this helps expose those very fine lines and intricate details. We use Italian mesh yellow and white, they are great for fine halftones with high resolution and has the greatest possible exposure latitude with unsurpassed protection against light-undercutting.

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.

When should I use Yellow Screen Printing Mesh?

When should I use a yellow screen printing mesh?

 20140721_105635

When you are doing fine detail is the short answer. Generally speaking there is very little difference in the performance of the mesh unless you are using 90T upwards. Yellow mesh absorbs more light and stops light scattering, this helps expose those very fine lines and intricate details. We use Italian mesh yellow and white, they are great for fine halftones with high resolution and has the greatest possible exposure latitude with unsurpassed protection against light-undercutting.

 Mesh Yellow.

Getting the right mesh count is like getting the right squeegee and the right ink for the job in hand. These are ALL really important and make the difference to your finished product. Remember what you are trying to do is push the ink through the mesh on to the substrate. So the wrong mesh will result in too much or too little ink getting through. Not good. A very detailed design on a coarse mesh won’t work either.

 Check out our range of screens and mesh.