HV fabric colour and heat transfer: why sublimation destroys fluorescent dyes
Why your HV garment is staining your customer's heat press — and what to specify in the tech pack to prevent it.
The Problem Nobody Talks About
A few weeks ago I received a message from a European workwear brand with a problem that, in theory, shouldn't exist: the high-visibility vest they had produced in Bangladesh was staining the transfer press of one of their end customers. The machine was turning yellow. The orange fluorescent fabric was losing colour when heat was applied.
This is not an isolated case. It's one of the most common problems in HV garments and one of the least understood by brands designing from an office in Europe.
What Is Actually Happening
Fluorescent fabrics — those oranges and yellows that comply with ISO 20471 and EN 471 — achieve their effect with specific dyes that react differently from conventional dyes. They are more sensitive to heat. Much more.
When an end customer tries to apply a heat transfer onto an HV garment, they apply heat, pressure and time. If the fabric hasn't been dyed with the correct parameters, or if the transfer temperature exceeds the thresholds the dye can withstand, the pigment migrates. It migrates toward the protective paper, toward the press plate, and visually the garment loses colour intensity.
The technical reason: the thermal stability of fluorescent dyes is significantly lower than that of standard dyes. Above certain temperatures — and here each colour behaves differently — the fixing process partially reverses itself.
The Temperature Threshold Matters More Than You Think
In standard production, a transfer press operates comfortably at 160–180°C. For conventional garments, that range is completely safe. For fluorescent HV fabrics, that same temperature can be the line between a correct garment and a claim.
What we've learned working with factories in Bangladesh and Myanmar is that the problem is rarely in the fabric itself — the fabric is well-dyed, it passes the fastness tests required by the standard. The problem is in the downstream personalisation process: the transfer that the distributor or end customer applies without knowing that this fabric behaves differently.
The solution is not only technical. It's also about communication.
What You Can Do as a Brand
First: specify the recommended temperature range for transfers in the technical data sheet. Don't take it for granted. If the garment is going to be personalised — embroidery, screen printing, heat transfer — add a technical note on the care label or in the product documentation. Something as simple as "maximum transfer application temperature: 150°C / 10 seconds" can prevent a full-scale claim.
Second: test with the end customer's actual process, not just the production process. In the factory, fastness tests are done according to standards. But if your end customer is going to use a 170°C press with 15 seconds of contact, that's the test you need to do before confirming production.
Third: differentiate between colours. Not all fluorescents behave the same. Lemon yellow has different stability from HV orange, and orange from fluorescent red. When there's a mix of colours in the collection, don't assume the behaviour is uniform. Test colour by colour.
Fourth: ask the factory for the correct application procedure. A good production partner — in Bangladesh, Myanmar or anywhere else — should be able to give you a clear protocol: temperature, pressure in kilos, time in seconds, and if necessary, a cooling period between the first and second press so the transfer adhesive penetrates properly into the fibre.
The Real Failure Is Not the Fabric
This is what I want you to take away: in the majority of cases I've seen, the fabric doesn't fail. The fabric complies with the standard. The problem is that nobody in the chain — not the brand, not the distributor, not the end customer — knew that this fabric needs different treatment.
High visibility is not just a question of standards and retroreflective tape. It's a technical category that requires understanding material behaviour under real conditions of use and personalisation.
The sooner you understand this and incorporate it into your product development process, the fewer surprises you'll have in season.