DiamondFinish Clear is a moisture-cured urethane, and small bubbles (micro-bubbles) in the coating film are a known application issue — but the fixes are simple. Understanding what causes them is the first step to a flawless finish.
WHY MICRO-BUBBLES FORM Solvent (thinner/reducer) becomes trapped in the coating film when the surface layer skins over too quickly — preventing normal evaporation. The trapped solvents vaporize within the film and push through the surface, leaving bubbles, pinholes, or craters. |
Common Causes of Micro-Bubbles in DiamondFinish Clear
1 — Not Stirring Before Each Application Even though it's a clear coating, DiamondFinish Clear must be stirred gently and thoroughly before every coat. Proper stirring disperses settled resins and additives, ensuring consistent adhesion and cure. Pro Tip: Stir by repeatedly touching the bottom of the can and lifting — do not shake. Shaking introduces air bubbles that will negatively affect the finish. Continue stirring often throughout use. |
2 — Applying Coats Too Heavy DiamondFinish Clear must be applied in thin coats only. A medium or heavy coat causes the outermost layer to skin over before solvents can escape, trapping them in the film. Build desired thickness with multiple thin coats — never heavy or medium passes. |
3 — Recoating Too Soon If a subsequent coat is applied too soon, solvents from the previous coat become trapped under the new film and cause micro-bubbling. Wait until the prior coat is dry-to-touch and leaves no fingerprint — typically 2–4 hours depending on temperature and humidity. |
4 — Excess Humidity in the Air High humidity (above 85% RH) causes DiamondFinish Clear to skin over too quickly, trapping solvents. To slow the cure rate, thin the coating 10–30% with KBS #1 Thinner or Xylene — or apply when humidity is more favorable. |
5 — Trace Moisture on the Surface Trace moisture on the substrate — especially porous surfaces — can cause micro-bubbles. Always dry the surface thoroughly before applying DiamondFinish Clear. Important: Ensure surface and air temperatures are within a few degrees of each other. Surface temperature must be at least 5°F above the dew point to prevent condensation. |
6 — Overworking the Brush or Roller Repeatedly rolling or brushing the same area forces DiamondFinish Clear to cure too quickly on the surface, creating a skin-over layer that traps solvents. Apply to an area and move on immediately — do not go back over the same section repeatedly. |
How to Fix Micro-Bubbles in DiamondFinish Clear
Sand the affected area smooth with 320-grit or finer sandpaper, then recoat. Wait to sand until DiamondFinish Clear has cured enough that the sandpaper does not gum up. When recoating, thin 10–20% with KBS #1 Thinner or Xylene to improve flow-out and relieve surface tension.
PRO TIP — THINNING FOR FLOW-OUT Thinning with KBS #1 Thinner or Xylene at 10–20% slows skinning and allows the coating to level and flow out properly — a helpful technique any time conditions are warm, dry, or the application area is large. |
Ready for a Flawless Finish? Pick up DiamondFinish Clear or KBS #1 Thinner and get the professional results your project deserves. |