Quick answer: In white UV coatings, buyers should start with the pigment burden and the real light source before they compare product names. Fotoinitiator 819 DW is the strongest first review point when the system is water-based or built around white and high-hiding-power pigments that need easier dispersion and stronger through-cure support. Photoinitiator 819 deserves earlier attention when the coating is thicker, more pigmented, or under deeper-cure pressure in a broader UV or UV LED route. Fotoinitiator DETX moves up when the process is better matched to a longer-wave class II route and the formulation can support co-initiator design.
That is the practical buying split. White UV coatings are not a good place for generic photoinitiator lists because titanium dioxide and other high-hiding-power pigments change the shortlist fast.
Why white UV coatings need a different shortlist
White UV coatings usually become harder to cure cleanly than clear systems because light penetration drops once the formula carries more hiding power. In practice, buyers are often narrowing the choice around four real constraints:
- Pigment burden: white and other high-opacity systems reduce how much light reaches deeper into the film.
- Through-cure pressure: thick white coatings and pigmented layers need more than a fast surface set.
- Yellowing control: the coating still needs acceptable appearance after cure.
- Lamp fit: a strong product on paper can still be a weak first sample if the wavelength match is poor.
If you need the broader family view first, start with Longchang’s photoinitiator selection guide.
Quick shortlist: 819 DW vs 819 vs DETX for white UV coatings
| Produkt | Best first fit | Why buyers shortlist it | When it is not the first option |
|---|---|---|---|
| Fotoinitiator 819 DW | Water-based white or high-hiding-power coatings | Longchang positions it as a stable water dispersion of 819, easy to mix into water-based systems, with direct use in white paints, colored paints, and inks containing titanium dioxide or similar hiding pigments | When the project is not water-based and does not need dispersion-led handling advantages |
| Photoinitiator 819 | Thicker white, pigmented, or harder-to-cure UV coatings | Broad 370 to 450 nm positioning, deep-cure support, low-yellowing framing for white or light-colored systems, and UV-LED relevance on the current Longchang page | When the main challenge is a water-based dispersion route or a formulation intentionally built around a class II co-initiated package |
| Fotoinitiator DETX | Long-wave or visible-light-leaning white coating systems with co-initiator support | Current Longchang page positions DETX for white coatings, thicker films, reduced yellowing, and response around 385 nm with 405 and 420 nm LED relevance | When the formulation cannot support the co-initiator logic required by a class II route |
When Photoinitiator 819 DW is the better fit
819 DW should move to the front when the white UV coating project is not just pigmented, but also water-based or handling-sensitive.
- Water-based route is already supported: Longchang describes 819 DW as a dispersion of 819 in water that is easy to mix into water-based systems and forms a stable dispersion.
- White-paint relevance is explicit: the current page directly positions it for white paints, colored paints, and inks containing titanium dioxide or other high-hiding-power pigments.
- Through-cure support: the same page states that 819 DW has excellent absorption properties and can be used in thick-film systems.
- Yellowing control matters here too: Longchang also frames 819 DW as helpful for UV yellowing resistance in these pigmented systems.
If the buyer is working on a white water-based coating and wants a product path already positioned for both pigment burden and easier incorporation, 819 DW is usually the strongest first review point.
When Photoinitiator 819 is the better fit
819 deserves earlier attention when the white coating is under stronger deep-cure pressure, or when the project is not mainly a dispersion-handling problem.
- Deeper-cure support is already supported: Longchang’s current 819 page highlights deep curing and a bleaching effect that helps light penetration.
- White and light-colored systems are already supported: the same page describes minimal yellowing and suitability for white or light-colored systems.
- Pigmented systems are already supported: Longchang positions 819 for thick coatings and pigmented systems, which makes it commercially relevant when white opacity starts to block cure-through.
- Broader UV and UV LED relevance: the current page also positions 819 for broad 370 to 450 nm absorption and UV-LED light sources.
If the white coating team needs a stronger deep-cure route for thicker films, harder penetration, or UV LED screening, 819 usually deserves earlier sampling than a routine clear-system benchmark.
When Photoinitiator DETX is the better fit
DETX belongs in a different selection path from 819 or 819 DW because the mechanism changes. It becomes more relevant when the process can use a class II route and the longer-wave response matters commercially.
- Mechanism clarity is already supported: Longchang states that DETX is a class II hydrogen-abstraction photoinitiator and needs co-initiators such as tertiary amines.
- Long-wave response matters: the current page places DETX around 385 nm and notes response to 405 nm and 420 nm LEDs.
- White-coating fit is already supported: Longchang explicitly positions DETX as stronger in colored systems, especially white coatings, and in thicker films.
- Reduced-yellowing framing: the same page also ties DETX to lower-yellowing white-coating selection logic.
If the buyer is screening a white UV coating route that benefits from longer-wave response and a co-initiated package, DETX is often the more relevant first comparison than a type I-only shortcut.
How buyers should shortlist before requesting samples
1. Start with the lamp and wavelength window
Changhong’s own coating-selection guidance emphasizes that the photoinitiator absorption band should match the emission band of the light source. In practical terms, that means white coating selection should start with the real lamp, not with the most familiar catalog name.
2. Judge whether the real bottleneck is water-based handling or cure-through
If the main issue is a water-based high-hiding-power system, 819 DW deserves earlier attention. If the main issue is deeper cure in a thicker white film, 819 often becomes more important.
3. Decide whether the formula can support a class II route
DETX should not be shortlisted as if it behaves like a type I product. If the formulation cannot support co-initiator design, remove it early.
4. Keep yellowing visible in the decision
White coatings can look cured and still fail commercially if the appearance target moves in the wrong direction after cure.
5. Keep the first sample round tight
In white systems, a cleaner first answer usually comes from comparing only the 2 to 3 most relevant routes, not from testing a long mixed list.
For the broader coating workflow, also see Selection of Photoinitiators in UV Coating Formulations. If the buyer is still deciding between reaction paths first, the live comparison of free-radical and cationic photoinitiator routes is the better starting point.
Recommended Longchang product paths
- Water-based white and high-hiding-power route: Fotoinitiator 819 DW
- Deeper-cure white pigmented route: Photoinitiator 819
- Long-wave co-initiated white-coating route: Fotoinitiator DETX
- Optional type I long-wave reference: Fotoinitiator TPO
- Broader coating guide: Selection of Photoinitiators in UV Coating Formulations
- Broader family guide: How to choose a photoinitiator for UV curing
FAQ
Which photoinitiator is best for white UV coatings?
There is no single best answer. In Longchang’s current product set, 819 DW is the strongest first review point for water-based white and high-hiding-power systems, 819 is stronger for deeper-cure white pigmented coatings, and DETX becomes more relevant when the formula is designed for a co-initiated longer-wave route.
Why are white UV coatings harder than clear systems?
Because titanium dioxide and other hiding pigments reduce light penetration, which makes cure-through harder and changes which photoinitiator route deserves first review.
When should I start with 819 DW instead of 819?
Start with 819 DW when the coating is water-based and the formulation team wants a stable dispersion route already positioned for white and high-hiding-power systems. Start with 819 earlier when the deeper-cure demand is the bigger bottleneck.
When should I move to DETX?
Move to DETX when the line benefits from longer-wave response and the formulation can support the co-initiator logic required by a class II photoinitiator.
Need a tighter shortlist for white UV coatings?
If your white UV coating project is being limited by titanium-dioxide burden, deeper-cure pressure, yellowing, or lamp fit, define that bottleneck first and then compare only the most relevant Longchang product paths. That usually gives a faster and cleaner sampling decision than treating white coatings like a standard clear-system screen.