Dye migration in textile transfers
When applying textile transfers to polyester, the transfers may become discoloured. This is due to the dyes used to dye the fabric. These dyes migrate from the fabric to the surface of the transfer. There are four distinct scenarios:
1. No polyester or polyamide in the textile
-> no dye migration
2. Sublimation-dyed polyester (coloured on the outside, white on the inside)
-> 99% of the sublimation pigments are bound within the fibre. In this case, a low transfer temperature can help to prevent migration.
3. Disperse-dyed polyester (coloured on both the inside and outside)
-> depending on the quality of the fabric, there may already be a significant amount of dye on the surface of the fibres which can migrate. Consequently, migration can occur even if the transfer temperature remains below 130°C. A sublimation blocker is therefore required.
4. Softshell textiles
-> These are usually disperse-dyed. Furthermore, they are mostly made of microfibres, which have a significantly larger active surface area to which an extremely large number of colour pigments can adhere. Consequently, depending on the quality of the fabric, migration can occur despite the use of a sublimation blocker.
Unfortunately, colour migration occurs very frequently, particularly when applying transfers to softshell jackets. The problem also generally arises when transferring, for example, white flex foil onto red football shirts, where the flex turns red because the heat reactivates the sublimation process.
With softshell textiles, however, this problem is insidious in that it does not occur immediately; it can sometimes take up to three months for migration to begin, which is due to the specific surface structure of this material.
As a general rule:
- It is best to advise your customers against using flex or flock for finishing, as, on the one hand, the jackets are often very expensive and, on the other, they vary greatly in quality, which in turn affects how the finish behaves. Embroidery is the better solution here.
- If flex finishing is to be used, then only with flex films featuring a Subliblock coating at a maximum temperature of 130°.
- The textiles must be washed several times before heat pressing.
- A test run should always be carried out, as follows:
1. Pre-wash the fabric a few times
2. Transfer the flex film with a Subliblock coating at a maximum temperature of 130°
3. The finished jacket must then be placed in a heat chamber or, alternatively, in the oven (who actually does that?) for 7–8 days at a temperature of 40–60° Celsius. If the fabric shows no signs of migration afterwards, production can begin.
