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
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.
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.
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
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
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!
Or even let us do it for you with our exposure service.
What heat press should I buy?
A common question but the answer is rarely straight forward as there are many factors to consider.
What is a heat press.
A heat press is a machine engineered to imprint a design or graphic on a substrate, such as a t-shirt, with the application of heat and pressure for a preset period of time.
Where does it fit in the process.
1, Choose an image to put on a product like a t-shirt
2. Print onto heat transfer paper
3. Lay the image on your t shirt
4. Use a heat press to transfer the image on the t shirt.
Which heat press should you buy
What are you going to use it for? Garments (T Shirts, Hoodies, Caps), promotional items (mouse maps, phone cases etc) , DTG preparation and curing, sublimation, Vinyl, Plastisol transfers etc Heat Presses are involved in all of these process however there are a few areas to consider before parting with your money
So here are some of our views …
Accurate Heat – to get the best results a heat press needs to maintain accurate and consistent heat across the platen. Too little heat may not activate the adhesives to fully fix the graphic to the garment, too much heat can affect the graphic quality, reducing opacity or not giving an even cure.
Digital control – needed to ensure you have accurate temperature you don’t want fluctuating temperatures, you need accurate timings and therefore consistent results. Many digital controllers come with timers and safety features such as auto shutdown and alarms.
Even pressure – uneven pressure will lead to poor adhesion and inconsistent curing of ink therefore always choose a press which you can adjust and set for different thickness of substrates. Some presses have pressure gauges which are ideal for ensuring consistent results.
Size of the Heat Press – there are many sizes to choose from and a key question to ask when buying a press is ‘What is the largest size of garment / substrate will I be using?’ It normally makes good sense to buy a press that can accommodate future needs. It’s also easier to align garments on a larger press. Some presses come with interchangeable platens which gives you much more flexibility.
Clam or swing away?
- A clam has a smaller footprint, when using a swing away you need to give space for the swing which on the bigger units can be quite significant
- A clam is typically less expensive than a swing away and less moving parts
- It is easier to see what is going on with a clam, if a garment has gone out of alignment you can do something about it
- Clam presses are typically more portable
- Swing aways different from a clam with the heating element lifting up parallel and swings completely out of the way.
- It is often stated that with a clam press to increase the chances of burned knuckles with the clam however with a swing away it is just as easy to get the fingers in the way. Quality clam presses open wide enough to reduce the chance of accidents.
- Swing aways are often more popular with DTG printers but you can also use a Clam
- Swings aways typically can be set to give more pressure than a clam, we have found that some transfer papers don’t work well on clams
- You can debate this but it really does come back to personal preference and budget. The simple answer is choose the press that suits your needs.
Budget – always choose a press with a lifetime heater warranty, with CE certification (real Certification (beware some of the cheap China imports are not made with high quality components and may not be actually certified compared to European / US presses). It’s better to buy the right equipment first time out rather than the cheapest – quality equipment is designed to last years with warranty backup if there is a problem. You will often find broken low quality heat presses lurking in the back of many print shops. If your business is reliant on the equipment then consider the impact of the heat press breaking.
If you have questions at all please contact us to discuss your requirements
Designed for the medium size print screen printing market the FREEstyler DTS is breaking new ground, using inkjet technology it will introduce Direct to Screen capabilities to the medium sized screen printers. The integrated exposure option includes an integrated LED exposure unit and stand.
You place an emulsion coated screen on the flat bed of the FREEStyler (it comes with various clamps that came be used to aid registration), you then control how the stencil is printed using RIP software that comes with the system. It replaces the Film Positive printing process, the FREEStyler uses inkjet technology to print the artwork directly on the screen with a quick drying ink which is water soluble. When completed you pop the screen in the exposure unit underneath, whilst the FREEstyler creates your next screen, you then take the exposed image and washout as per normal.
Designed for the small and midmarket with an appropriate pricing structure, supports frames up to 36” x 26”, (creates stunning stencils Resolution from 600 – 2400 dpi, 55 – 60 lpi) which would be difficult to achieve accurately with film positives printed with an inkjet printer
The FREEstyler is virtually maintenance free. Unlike most ink jet to film devices and more expensive direct to screen systems the FREEstyler uses a disposable ink cartridge with no complicated ink feed system. It will support frame sizes up to 36″ x 25″.
FREEstyler DTG mode, you can purchase an optional DTG upgrade kit which includes platen, RIP extension, process ink and cartridges. So you can use the FREEstyler both for printing direct to garment as well as direct to screen.
The exposure unit can handle screens up to 110 x 80cm. It uses UV-LED bulbs (Full array of 9 x 11 rows – 390nm wavelength). Typical exposure times are 30 – 60 seconds (Pure Photopolymer), 120 – 150 seconds (Dual Cure) and 180 – 300 seconds (Diazo emulsions).
To see the promo video click here.
Standard unit comes with 23 x 31″ screen drum kit and 2 sets of black UV cartridges
When should I use a yellow screen printing mesh?
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.
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.
A great Australian blog about screen printing with kids. All the equipment can be bought at Wicked Printing Stuff🙂