In this blog post we answer the following questions: Why do some heat transfers include a migration blocker? What is the correlation between sublimation and a migration blocker? Why can this be a problem during the production process of a textile or fabric? How do we solve this problem? Which textiles, fabrics and garments may this affect? What do I have to consider during the design process?
If white textiles or fabrics are to be coloured, there are various options. One of them is sublimation, where paint evaporates from carrier paper at 200°C and becomes solid on the textile or fabric fibres. However, this process only works with polyester or mixed fabrics where other dyeing processes use natural fibres, such as cotton.
Heat transfers are applied to a finished garment at temperatures between 120°C and 200°C. A previously sublimated textile or fabric reactivates at high temperatures. It partially turns back into steam and works its way through the various layers of the heat transfer. It then solidifies again and can be seen as spots in the design of the heat transfer. This process can be slow and you may not notice anything shortly after the application. Only after a few months, the familiar "migration spots" suddenly appear, they look similar to coffee stains.
Problems are there to be solved: Our solution is a migration blocker. This migration blocker is a protective layer that is incorporated into the structure of the heat transfer. Most of the time, the protective layer is just above the adhesive layer where it forms the barrier for the evaporating paint.
Where migration blockers used to be made of a black colour layer or layers made of metallic powders (such as silver or gold), today’s migration blockers are an active carbon layer. Active carbon, consists of large particles that work similar to a sponge, they grab the migrating colour particles and lock them in. Another benefit is the high level of elasticity that is created, which ensures the use of heat transfers on stretchable fabrics, like sports garments.
The active carbon layer is set directly over the adhesive layer so that all other layers of the heat transfer are protected from the migrating colour of the textile, fabric or garment. For a better understanding, here you can see the lateral cross-section of a heat transfer enlarged 30 times.
The picture shows our quality 3D SILICONE X TATAMI where the layers build up from bottom to top as follows: glue (white), sublimation blocker (black), undyed tatami, coloured tatami (purple), undyed silicone and coloured silicone (white).
Special cases need special solutions: For extremely stretchable garments, like swimwear, gymnastics garments, etc., the already stretchy active migration blocker is not stretchy enough. We came up with a revolutionary invention. To not be dependent on the active carbon migration blocker, we constructed ECOBLOCK WHITE. Consisting of a special silicone material that contains a natural migration blocker. Therefore, no extra layer of migration blocking material is needed, which makes it extremely thin. That offers greater stretchability than heat transfers with an active carbon migration blocker.
Let’s answer the most frequently asked question: When is the migration blocker necessary? Here’s a simple roadmap that will help you:
1. Is your textile, fabric or garment, dyed in a different colour than white?
2. Is your textile, fabric or garment, made of mixed fabrics or polyester?
3. Is your garment a softshell jacket?
If you answered YES to at least one of these questions, we will most certainly include a migration blocker in your request.
Let's summarize everything briefly: Sublimated textiles, fabrics and garments, are no obstacle for an embellishment with heat transfer printing techniques! A migration blocker prevents a heat transfer from being discoloured by the application or washing processes. It is located in the second-deepest layer of the heat transfer structure. It is required for the embellishment to textiles, fabrics and garments that have been coloured by sublimation before (mixed fabrics, polyester textiles) or for textiles, fabrics and garments that have a special structure (softshell jackets, coated rain jackets).