Wondering how to print polyesters? This article, edited by Master Screen Printer, Douglas Grigar can guide you through the process.
Just how troublesome can screen printing polyester really be?
Very, very troublesome!
Whether you are new to screen printing or an old hand, printing onto athletic and performance wear made of high polyester content can be a monumental headache. The higher the polyester content and it’s dye or colour, the more potential problems! In this article we explore how to print polyesters in a way that will minimise the headaches.
The problem on the garment happens in three stages. Heat during curing of the garment causes the dye in the fabric to turn to gas (sublimation), which causes the colours to migrate through the ink layer and show up as a visual bleed. So dye sublimation, dye migration and colour bleed are all terms used to describe the same problem.
What could a mistake cost?
There is a very real threat of colour bleeding from the fabric to the ink and causing a tinge or taint. Think about a red shirt with a crisp white print…. A bit less exciting when that crisp white print turns pink on you and your customer turns a funny shade too. You could be faced with a very significant loss when you have to replace expensive shirts and reprint them too.
Step 1: How to print polyesters: The correct ink
In knowing how to print onto polyesters, it is very important to use the correct type of ink. Ink manufacturers know how problematic these fabrics are and have spent many hours researching solutions to make your life easier.
Choose high quality ink that is intended for screen-printing onto polyester and you are starting to stack the odds in your favour. Careful control according to manufacturers directions is essential. One example of a white ink for screen printing on polyester would be Miracle White by Lancer.
Step 2: Consider using a first-down “defender”
A first-down defender is a special ink intended to be used with the real troublemakers in fabrics. This ink actually helps to block and filter out any dyes that may migrate from the garment to the ink. You can use a defender like this for direct printing (first-down as the primer or under-base) or when you are printing transfers (last-down). Lancer produce a defender in both pvc-free and standard phthalate-free plastisol ink.
Simply print your other colours over the defender.
Step 3: Curing and heat control is critical!
Another crucial factor when considering how to print polyesters correctly is to get the curing right. Heat curing polyesters prone to dye migration is far more temperature sensitive with a much smaller window of working temperature variation.
Use a laser temperature gun or temperature probe to measure the temperature of the ink film before it exits the dryer to ensure it has reached the correct temperature. You will need to check what the manufacturer of your ink recommends.
You must continue to monitor this temperature throughout the production period to ensure control is maintained within the specified range.
If you are curing with a flash cure unit only there are a few additional points to consider. First of all make sure you stay well within the curing area of the unit to avoid under-cured areas on the periphery of the printed area.
A good quality flash cure unit should have very even temperature across the entire cure area and that will certainly help with consistency. Curing really heavy ink deposits with a flash cure only is asking for trouble and should be avoided.
Step 4: Additives worth considering
Depending on the ink range you are using, you may find handy additives to help out with tricky situations. When it comes to printing onto polyester, you can try using a low cure additive that will lower the temperature at which the ink cures. Curing at a lower temperature is an aid to minimising dye migration or colour bleed.
If you are printing a poly-cotton blend rather than a 100% polyester, you may find that adding a low bleed additive to your normal ink that is intended for cottons may be all that is needed. Experimentation is key!
No matter what – test, test, test!
The best advice we can give when you consider how to print polyesters…..unless you have done the exact same print job onto the exact same fabric with the same ink before and you already know all the parameters…..TEST – TEST – TEST! Use the suggested steps above or if you prefer to follow our shortened article: Screen Printing Onto Polyester: Suggested Protocol
We have also done a follow-up article: Printing 100% Polyester: Wash Tests Done To Nike Standards to illustrate the end results after wash testing.
It will save you a lot of pain and potential lost revenue and goodwill later on.
If you have any questions about screen printing, please contact us. We are happy to help with your technical issues.