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Home / News / Industry News / Coating Surface Feels Rough and Develops Cratering — How to Improve Both at Once?
Industry News
In wood coatings, industrial coatings, and curing coating systems, film surface state directly affects the final coating experience. Some formulations show a basically normal film after application, but feel rough to the touch; some coatings readily develop uneven wetting or cratering during application; matting systems in particular may develop uneven gloss if surface state changes significantly. These phenomena all occur at the film surface — but their causes are not identical, and the adjustment logic for each is different.
Common Surface Problems and What They Signal
Cratering After Spray Application
Cratering is related to the coating's spreading state on the substrate. If local wetting differences cause uneven film flow, the wet film may retract in some zones — forming visible depressions. Especially sensitive on low-surface-energy substrates.
Film Looks Flat but Touch Is Rough
"Looks flat" and "feels smooth" are not the same property. Film leveling addresses visual flatness; surface slip involves the friction state at the surface. A formula with good leveling may still feel rough — requiring separate adjustment from the surface additive direction.
Uneven Matting in Matting Systems
Matting powder needs to form a stable surface state during film formation. If surface tension changes, matting powder rearrangement, or flow inconsistency occurs, local gloss differences may appear — particularly visible in large-area flat panel application.
Additive Addition Level Difficult to Balance
Surface additives with strong interfacial activity are not better in larger amounts. Too low an addition may not produce the expected surface adjustment; too high may change the coating's surface state and affect subsequent recoat and interlayer performance.
Why Surface Adjustment Requires Looking at the Full Film Formation Process
When encountering cratering, the tendency is to increase leveling agent; when encountering rough surface feel, slip additives may be continuously increased. This adjustment approach is direct but, without distinguishing the problem source, easily produces "fix one thing, another appears" situations. Substrate wetting, film spread, surface flow, drying, and final surface feel are different stages — different stages require different adjustment directions. Only by separating these stages can the additive adjustment be more targeted.
DH-4500: Polysiloxane-Polyether Copolymer Surface Additive
DH-4500 is a polysiloxane-polyether copolymer that improves substrate wetting by changing the coating's surface state, while also taking into account the slip feel of the film surface. In actual formulations, addition level can be selected based on the system type.
Reference Addition Ranges by System
Solventborne Wood Coatings
0.05%–0.3%
Focus on wetting, surface feel, and cratering
Waterborne Wood Coatings
0.05%–0.5%
Also observe storage and recoat performance
Curing Systems
0.1%–0.6%
Focus on post-cure flatness, slip feel, and surface defects
Solventborne Industrial Coatings
0.1%–1.5%
Further adjust based on substrate, resin, and application method
It can be added directly or pre-diluted before addition. For different formulations, gradient addition is recommended rather than fixing a single ratio at once. Testing should simultaneously observe: substrate wetting, cratering count, film flatness, surface feel, gloss change, and matting uniformity — making it easier to judge which specific stage the additive has improved.
Film surface slip feel is not determined by a single material alone — substrate wetting, surface tension, leveling state, and film formation process all contribute. When a formulation shows simultaneous wetting deficiency, cratering, rough surface feel, or uneven matting, the surface state should be re-examined holistically rather than simply adding more of one leveling material. DH-4500 is applicable to waterborne, solventborne, and curing coating systems — the appropriate formulation ratio can be found through gradient addition combined with the specific resin, substrate, and application conditions.
Frequently Asked Questions
Can DH-4500 simultaneously improve both cratering resistance and surface slip in the same formulation?
Yes — this is the intended multi-functional characteristic of polysiloxane-polyether copolymer additives. The polyether component provides compatibility with the resin system and improves substrate wetting; the polysiloxane component provides surface slip and reduces surface friction. Both functions are delivered through the same additive at an appropriate addition level. The relative balance between wetting improvement and slip improvement shifts with addition level — at the lower end of the range, wetting improvement is typically more pronounced; at higher addition levels, the slip contribution becomes more significant.
Why is the addition range for industrial solventborne coatings (0.1–1.5%) so much wider than for wood coatings (0.05–0.3%)?
Industrial solventborne coatings span a much wider range of resin types, viscosity profiles, substrate materials, and application methods than wood coatings — from thin-film decorative topcoats to heavy protective coatings. This wider formulation diversity means the amount needed to achieve the target surface state also varies more broadly. Wood coating systems are more constrained in formulation type and application method, meaning the effective range for surface performance optimisation is narrower and more consistent across formulations.
