Powder Coating Colors: RAL, Gloss and Texture

A small square on a color chart turns into three decisions on the shop floor: the RAL number, the gloss level, and the texture. If any one of them is left unclear, the production batch can drift away from the approved sample. This article walks through the color chart in order and explains how to specify, verify and hold each item.

A RAL number is the starting point, the sealed sample is the verdict

RAL is the industry-standard public color system for powder coating. Each four-digit code maps to one color, which makes communication easy: RAL 7016 means the same grey to both sides.

That said, a RAL number alone should not serve as the acceptance standard, for three reasons:

• The same number looks slightly different across resin systems - epoxy, polyester and epoxy-polyester hybrid all match the chart, but placed side by side they differ;
• Color charts fade. A square that has sat in a display case for years no longer represents the factory condition;
• Normal batch-to-batch variation exists between powder lots, within accepted industry tolerances.

The common practice is: the RAL number sets the direction, the sealed sample sets the verdict. Before production starts, have the powder supplier spray a test panel on your actual workpiece, confirm it with both signatures, and check every production batch against that panel. The chart stays in the communication loop; the sample stays in the QC loop.

Gloss: define the level first, then talk color

The same color number at a different gloss level looks like two different colors. The industry generally grades coating gloss at a 60-degree measurement angle into three levels: high gloss, semi-gloss and matte. The exact cut-off points vary slightly between powder suppliers, so the safest move is to mark the gloss level on the back of the panel when ordering.

Two things to watch:

• Gloss drifts with film thickness and oven temperature. Two parts from the same batch with very different film thickness will show a gloss difference, so controlling gloss starts with controlling film thickness;
• Compare gloss under the same light source. Viewed under shop lighting versus daylight, the conclusion can flip. Fix one light source before comparing against the sample.

Texture: smooth, textured and metallic each cover a different job

Powders fall into three appearance classes. Pick the class by the workpiece first, then pick the color:

Powder class	Surface character	Typical workpieces	Process sensitivity
Smooth	Flat surface, true color rendering	Appliance panels, parts that need a clean visible face	Scratches, inclusions and craters all show
Textured (sand finish)	Sandy grain, hides substrate flaws	Guardrails, profiles, equipment enclosures	Film thickness affects grain sharpness
Metallic	Metal pigment, shifts with viewing angle	Decorative parts, aluminum profiles	Any change in spray conditions shifts the hue

Textured powders earn their place by swallowing small substrate marks and slight unevenness into the grain - the visible face stays clean and rework pressure drops. The trade-off is stable film thickness: too thin and the grain does not form, too thick and it blurs. Smooth powder is the opposite - it demands cleaner pretreatment and substrate condition. Metallic powder is the most condition-sensitive of the three, covered next.

Change the powder class, change the parameters

Different powder classes charge differently, so one voltage-current setting cannot serve them all. The following are commissioning reference ranges from the equipment manual; fine-tune on site by workpiece shape and target film thickness:

Powder / condition	Voltage reference	Current reference
Smooth powder	70-90kV	40-60μA
Textured powder	50-70kV	10-30μA
Metallic powder	60-80kV	30-50μA
Recoated parts	20-40kV	10-30μA

(Reference ranges per the equipment manual; follow the manual shipped with your gun.)

This “preset per powder class” logic is exactly what the data packages on digital controllers do - one stored setting each for smooth, textured and metallic powder, recalled with one touch to reduce manual setting errors. Switch the parameter set before you start spraying, not after the first reject.

Why metallic powder hue drifts

Metallic powder suspends aluminum pigment flakes, and the orientation and distribution of those flakes decide the angle-dependent color you see. With the same batch of metallic powder, any change in spray conditions changes the color. Keep these controls in place:

Drift factor	Shop-floor control action
Parameter drift	Lock one voltage, current and air setting per order
Gun distance and film thickness wander	Hold gun distance steady; keep film thickness within a narrow band
Fluidizing air too high	Pigment separates from the powder; fluidize to a rolling boil, no more
Unfixed recycled powder ratio	Fix the blend ratio; mix virgin and recycled powder consistently
Mixed powder batches	One order, one supplier, one batch
Mating parts sprayed separately	Parts that assemble together should be sprayed in the same batch

For industries where color consistency is critical, such as aluminum profiles, these points are daily practice. See the full scenario in aluminum profile coating.

When the batch does not match, check in this order

If a batch shows color difference, do not re-spray the whole load yet. Rule causes out from cheap to expensive:

Symptom	Check first	How to confirm
New lot differs from the sealed sample	Powder batch	Check the batch number on the packaging; spray two test panels
Parts within one batch differ	Parameter drift, gun distance	Pull the parameter log; measure film thickness on several parts
Color changes with viewing angle	Metallic flake orientation	Compare again from a fixed viewing angle
Overall lighter or darker	Film thickness	Measure and align with the sample thickness
Off-color after a changeover	Residual powder	Clean gun and pump, spray transition parts first

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Checklist

• The order states the RAL number, gloss level and texture class
• The sealed sample is signed and retained; the chart is for communication only
• Parameters switch with the powder class - no reusing the previous class’s settings
• Metallic orders lock batch, parameters and gun distance
• Recycled powder blends at a fixed, recorded ratio
• Mating parts are scheduled into the same oven batch
• Test panels come first; production starts only after matching the sample

A color chart alone cannot tell you how a powder will look on your workpiece. Send us the workpiece photos, dimensions and color requirements via the contact page - we can spray samples first and let the sealed sample decide the production run.