Guide
How do you write a powder coat appearance callout for color, gloss and texture?
A powder coat appearance callout is the part of a drawing finish note that fixes what the coated part looks like: a color reference, a gloss level in gloss units at a stated glossmeter angle, a powder coat texture named against a physical master sample, and the tolerance and viewing method used to accept all three. Without it, “black powder coat” is a request, not a specification.
By Saola Manufacturing engineering team · Published · Updated
This guide is for design and quality engineers who own the finish note, and for buyers who receive the parts. It does not cover how to choose powder coating over anodizing or plating, or how to keep the film on the part; those are covered in the guides linked at the end. It covers only appearance: the three attributes that a vague note leaves open, the test methods that pin each one down, and the wording that makes two suppliers, or two lots from one supplier, land on the same part.
On this page
Why does a note like “black powder coat” give mismatched parts?
Because it names a hue and nothing else, so every supplier fills in gloss, texture and shade from whatever powder is on its shelf. Two compliant suppliers can ship a flat sand-textured black and a glossy smooth black against the same note.
Powder manufacturers sell the same nominal color in many gloss levels and several textures, often from different resin chemistries. A coater reading “black” will reasonably pick its standard stock black. The mismatch shows up late: on an assembly where a bracket from one source sits next to a cover from another, or on a reorder after the coater switched powder batches or brands. Neither supplier is out of specification, because the specification did not say anything about the attributes that differ.
The fix is to treat appearance as three separately controlled characteristics, each with its own reference and its own acceptance method. Color is controlled against a named color standard plus a physical sample. Gloss is controlled as a number with a measuring angle. Texture is controlled against a master panel, because no numeric scale for it is in common use. A fourth item, the cosmetic surface designation, tells everyone which faces the first three apply to.
How should gloss be specified, and at which glossmeter angle?
Give a gloss range in gloss units and name the geometry, for example a 60° reading per ASTM D523. Words like “satin” or “semi-gloss” mean different numbers to different powder makers.
ASTM D523 measures specular gloss of nonmetallic specimens at three geometries, 60°, 20° and 85°, and its international counterpart is ISO 2813. The 60° geometry is the general-purpose angle. Per ASTM D523, a very glossy surface is better separated at 20°, and a very flat surface at 85°, because the 60° reading compresses differences at both ends of the scale. Gloss units are relative to a polished black glass reference, so a reading is only comparable with another reading taken at the same geometry.
A practical callout reads “GLOSS 25–35 GU AT 60° PER ASTM D523”. A band about ten units wide around the nominal is a common starting point for a mid-gloss powder; check it against the gloss tolerance on the powder data sheet before you fix it. ASTM D523 points to 20° when the 60° reading is above about 70, and to 85° when it is below about 10, so a dead-flat part should carry its gloss band at 85°. State where on the part the reading is taken: a flat area large enough for the instrument aperture, away from edges and holes, on a designated cosmetic face.
| Band name (varies by powder maker) | Approximate 60° reading (GU) | Geometry to specify |
|---|---|---|
| High gloss | above 70 | 20° |
| Semi-gloss | 40 to 70 | 60° |
| Satin / low gloss | 25 to 40 | 60° |
| Matte | 10 to 25 | 60° |
| Flat / dead flat | below 10 | 85° |
What does a RAL number control, and what does it leave open?
A RAL Classic number such as RAL 9005 identifies a color shade and nothing more. It does not fix gloss, texture or the powder chemistry, so the gloss and texture lines are still required.
RAL publishes its color collections as physical reference cards and fan decks. RAL 9005 (jet black) and RAL 9016 (traffic white) are sold by most powder makers in smooth gloss, smooth matte and several textures, and each version is a legitimate “RAL 9005”. Texture and gloss also change how the same pigment reads to the eye: a textured or flat finish looks lighter and less saturated than a smooth glossy one, which is why a color comparison is only fair between samples of the same gloss and texture.
The US federal color system, FED-STD-595, now maintained as AMS-STD-595, works differently: the first digit of its five-digit number encodes gloss class, so 17038, 27038 and 37038 are the same black at gloss, semigloss and lusterless. If your drawing already uses a 595 number, keep it, but still add a gloss value in units, since the class is a range, not a target. For either system, add the powder manufacturer and product code once a powder has been qualified. That single line removes most lot-to-lot drift, because a coater can no longer substitute an equivalent from another brand without asking.
Color difference, when it is measured rather than judged by eye, is calculated per ASTM D2244, which states that the purchaser and the seller shall agree on the permissible tolerance and the procedure for calculating it. The practice covers several formulas (CIELAB ΔE*ab, CMC, CIE94, DIN99o and CIEDE2000) and recommends CIEDE2000 (ΔE00) for small differences, so a bare “ΔE 1.0” can mean different things. A callout such as “ΔE00 1.0 MAX VS MASTER, D65/10°” names the formula, the illuminant and the observer; leave out any one of the three and the number cannot be checked. Where only a visual check is practical, ASTM D1729 sets the diffuse lighting, viewing conditions and observer color-vision requirements, and checking under two light sources catches metamerism, the case where two blacks match in daylight but not under shop lighting.
How should a drawing specify powder coat texture?
Name the texture type, tie it to the powder product code once one is qualified, and make a signed master panel the acceptance reference. No ASTM or ISO method in common use grades powder coat texture on a numeric scale, so the sample is the specification.
Texture types run from fine texture and sand texture through wrinkle, hammertone and veined finishes. They are chosen for function as often as for looks: a texture hides machining marks, die-cast flow lines and fingerprints, and it hides small variations in film build that would show on a smooth gloss face. The cost is that texture is sensitive to process. Film thickness, gun settings and cure all change how coarse the finish reads, and a reorder sprayed at a different film build can look like a different product even with the same powder.
Write the texture line in three parts: the descriptive type (“FINE TEXTURE”), the master sample reference (“MATCH MASTER PANEL 12345-CS-01, REV A”), and a film thickness band measured per ASTM D7091, which covers nondestructive dry film thickness measurement on ferrous and nonferrous metals. Typical powder films run in the 50 to 100 µm range, and textured powders are often applied at the heavier end; take the actual band from the powder data sheet rather than from a generic chart. Do not put a tight gloss number on a textured finish. ISO 2813 limits its gloss method to non-textured coatings on flat, opaque substrates, and in practice readings on texture are low and scatter with the measuring spot, so a gloss line on a coarse texture becomes a rejection generator rather than a control. Use the master panel instead, or a loose gloss band labeled for reference only.
Metallic and flake powders need the same treatment. ASTM D523 is written for nonmetallic specimens and ASTM D1729 places the viewing of metallic paints outside its scope, so both gloss and color for metallics are best controlled by a master panel viewed at the angles the end user will see.
What does a complete finish note look like on the drawing?
One note, one line per attribute, each line pointing at a reference or a test method. The example below can be copied and edited; every value in it is a placeholder to replace with your own.
Keep appearance lines separate from the protection lines (pretreatment, adhesion, corrosion testing), so that a cosmetic deviation and a functional one can be dispositioned separately. Mark cosmetic faces on the views with a flag or a surface designation, and state what applies to the rest: “NON-COSMETIC SURFACES: FULL COVERAGE, COLOR MATCH NOT REQUIRED” is a sentence that saves a lot of inspection argument.
| Line | Example wording | What it closes off |
|---|---|---|
| Process | POWDER COAT, POLYESTER, EXTERIOR GRADE | Resin swaps that change gloss retention outdoors |
| Color | RAL 9005 JET BLACK; POWDER MFR / PRODUCT CODE OR APPROVED EQUAL BY WRITTEN DEVIATION | Brand substitution between lots |
| Gloss | 25–35 GU AT 60° PER ASTM D523, READ ON SURFACE A | “Satin” meaning different numbers |
| Texture | FINE TEXTURE, MATCH MASTER PANEL 12345-CS-01 REV A | Coarse vs fine texture drift |
| Color tolerance | ΔE00 1.0 MAX VS MASTER, D65/10°, PER ASTM D2244; OR VISUAL PER ASTM D1729 | Undefined shade acceptance |
| Film build | 60–100 µm PER ASTM D7091, COSMETIC FACES | Texture and hiding changing with thickness |
| Scope | COSMETIC SURFACES AS FLAGGED; MASK THREADS AND DATUM B | Cosmetic rules applied to hidden faces |
What are the most common mistakes in powder coat appearance callouts?
The usual failures are a hue with no gloss number, a sample that nobody can identify later, and a measured color tolerance with no illuminant or formula. Each one leaves the supplier to decide what you meant.
- “Match sample” with no sample identity. A sample needs a part number, a revision and a custodian. Make at least two signed master panels, one kept by you and one by the coater, and replace them when they age or get handled; a panel that has sat in sunlight is no longer the color it was.
- Approving color on one gloss, ordering another. If the color sample is smooth gloss and the production part is textured matte, they will not look the same, and neither party is wrong.
- Gloss tolerance on a textured or metallic finish. See above; control those with the panel.
- Two suppliers, one note, two powders. When parts of one assembly are coated by different sources, name the powder product code on both drawings or require a joint side-by-side approval of production parts before release.
- No cure or batch control on the PO. Overbake shifts gloss and can yellow whites, and powder batches vary slightly. Ask that each lot ship with the powder batch number recorded and the cure run to the powder data sheet, and keep a retained part from each lot.
- Cosmetic rules on every face. Inspecting the inside of a housing to the same standard as its front panel adds cost and rejects without adding value.
What should the RFQ include, and how does Saola handle it?
Send the finish note, the flagged cosmetic faces, and either a physical master sample or a clear statement that one will be approved at first article. A gloss number and a color number on the drawing are not a substitute for an agreed sample.
Saola Manufacturing offers powder coating, alongside pad printing, through partner finishing plants it manages, as part of a fixed menu on the surface finishing page; the parts coated are usually die castings, stampings or parts machined at its lead CNC plant, and the quote names where each step is done. Per the quality page, parts are finished to the cosmetic standard you supply, whether a boundary sample, a written specification or marked-up photos, and if no standard is supplied Saola asks for one before production. Any cosmetic samples are reviewed and signed off by you at the sample approval step, before production runs.
Be plain about instrument readings. The capability and quality pages do not list a glossmeter or a color spectrophotometer, so do not assume gloss or ΔE readings will come back with a lot. If your drawing requires instrument values, raise it in the RFQ so it can be answered before the quote, in line with the surface finishing page’s request to say so before tooling when a specification calls for a finish or test the plant does not run. In every case, an approved physical master sample is the reference both sides can hold. The same page asks buyers to name the exact finish, to mark what must stay bare and to reserve cosmetic call-outs for visible faces, which matches the note structure above. When the drawing is ready, send it for a quote.
Frequently asked
Can I call out a print-ink color reference instead of RAL?
You can, but print-ink systems are defined on paper and inks, and powder makers can only approximate them. If the brand color comes from a print guide, have a powder matched once, approve a master panel, and then call out the powder product code and the panel rather than the ink reference.
Does film thickness or cure change gloss?
Yes. Cure temperature and time, film build and even line speed move gloss, and overbaking can also shift light colors toward yellow. That is why the note should ask for the cure to follow the powder data sheet and why a film thickness band belongs next to the appearance lines.
Where on the part should gloss be measured?
On a flat area of a designated cosmetic face that is larger than the glossmeter aperture, away from edges, holes and corners. Curved or narrow parts often cannot be read at all; for those, call out gloss on a coated test panel sprayed with the lot and judge the part against the master sample.
Is a gloss value enough without a master sample?
For a smooth, nonmetallic finish it controls one attribute well, but not shade or texture. A master sample covers what the numbers cannot, and the numbers keep the master sample honest as it ages. Use both.
Sources
- ASTM D523, Standard Test Method for Specular Gloss, ASTM International, D523-25 (2025)
- ISO 2813, Paints and varnishes: Determination of gloss value at 20°, 60° and 85°, ISO, 2014
- ASTM D2244, Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates, ASTM International, D2244-23 (2023)
- ASTM D1729, Standard Practice for Visual Appraisal of Colors and Color Differences of Diffusely-Illuminated Opaque Materials, ASTM International, D1729-22 (2022)
- ASTM D7091, Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals and Nonmagnetic, Nonconductive Coatings Applied to Non-Ferrous Metals, ASTM International, D7091-22 (2022)
- RAL color collections, RAL gGmbH, accessed October 2026