What are blocker transfers?

The background to blocker transfers

There is a whole range of garments that can cause so-called migration, or what some call “bleeding through”, on transfers, which damages the appearance of the print. What happens is that a chemical process occurs where the pigment in the dye that moves about on the transfer paper causes dark spots and shadows to appear on the transfer. It can also make the transfer print look as it if has bled or become mouldy.

What does migration mean?

Migration is generally used to describe the chemical process whereby the pigments in the dye move about on the transfer paper. The most frequently affected materials are polyester and softshell.

How can I combat migration?

We have produced an accessory to combat and minimise this phenomenon in the best possible way. We call this accessory a “BLOCKER” but it is often known as “block-out, block, blocking or black blocking”. This barrier is made up of several layers which are printed behind the motif, making the print thicker but also preventing migration in the majority of cases. Our blocker transfer is easy to recognise because it has a grey back, instead of white.

When do I need blockers?

As mentioned above, it is polyester softshell materials that are most frequently affected by this phenomenon, and we have also noticed over the years that after a while bleeding occurs in almost every case. But there are many other materials that are also affected by this problem. That’s why we ALWAYS recommend getting yourself a BLOCKER if you’re planning to apply transfer prints to these sorts of garments.

We recommend talking to your garment supplier to see if they have ever had any issues with migration. If you cannot get any information from your supplier, we will be more than happy to help you test your material in our test laboratory where you can get a test report.

Order blocker transfers

You can order Blockers for all heat transfers in the STARK & REFLEX range as an optional extra as part of the ordering process through our online store.

If you have a garment with a material which you know might cause bleeding through/migration, our recommendation is ALWAYS to use BLOCKER accessories. If you have any questions or concerns, please don’t hesitate to get in touch with one of our customer service team for more information and advice!