Acrylic Two-Pack Paint: The Complete Guide
What 2K acrylic paint is, how the chemistry works, and why it is the standard coating system for commercial aluminium windows and metalwork.
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Paint Systems & Finishes
Gloss Levels for Aluminium Windows: Matt, Satin, Semi-Gloss & Gloss Explained
Which finish level is right for your aluminium windows or commercial metalwork? We explain what each gloss level looks like, how it performs, and what our project data shows about what clients actually choose.
When you request a quote for aluminium window recoating or commercial metalwork spraying, one of the first decisions you will face is the gloss level of the finish. It is a choice that affects how the completed job looks, how it wears over time, and how it sits alongside the surrounding architecture, yet it is often treated as an afterthought.
This guide explains how gloss levels are defined and measured, what each level looks like in practice, and what the data from our own projects tells us about what specifiers and building owners tend to choose, and why.
How gloss level is measured
Gloss is not subjective, it is measured in gloss units (GU) using a glossmeter at a standardised angle. For mid-range finishes, the 60° measurement angle is standard. Very low gloss finishes are also measured at 85° to give a more discriminating reading in that range; high gloss is sometimes measured at 20°.
Paint manufacturers specify the gloss level of each product in their technical data sheets, and a trained applicator can verify the cured film using a calibrated glossmeter. This matters on commercial projects where a specification calls for a defined finish, "satin" on one manufacturer's product may be noticeably different from another's if gloss units are not specified.
Gloss level scale, 60° measurement (approximate)
Matt / Flat
<10 GU
Eggshell
10–25 GU
Satin
25–45 GU
Semi-Gloss
50–70 GU
Gloss
80+ GU
66%
of projects specify semi-gloss, the most popular choice by a clear margin
↑
Matt finishes are growing, driven by contemporary commercial architecture
↓
High gloss is declining, surface imperfections become more visible at higher sheen
Each finish level explained
The five main gloss levels available for 2K acrylic commercial metalwork each serve a different purpose. Understanding what they deliver visually and practically makes it easier to specify the right one for your building.
Matt
GrowingBelow 10 GU at 60°
Matt finishes have no perceivable sheen, the surface absorbs rather than reflects light, giving a flat, modern appearance. They are increasingly specified on contemporary commercial buildings, particularly where architects want the window frames to recede visually rather than draw attention.
- Conceals surface imperfections and minor substrate irregularities well
- Very popular on dark RAL colours (e.g. RAL 9005 Jet Black, RAL 7016 Anthracite Grey)
- Requires slightly more careful maintenance, more susceptible to surface marking than semi-gloss
- Fully suitable for exterior commercial use with 2K acrylic
Eggshell
Steady10–25 GU at 60°
Eggshell sits just above matt, a very low, barely perceptible sheen that adds a marginal amount of depth to the colour without introducing light reflection. It is a practical middle ground for specifiers who want a contemporary look without committing to a fully flat finish.
- Slightly easier to clean than matt
- Less forgiving of surface imperfections than matt, but more so than satin or semi-gloss
- Works well in sheltered locations and interior commercial metalwork
- Often preferred where specification calls for "low sheen" without full matt
Satin
Steady25–45 GU at 60°
Satin offers a soft, warm sheen, visible but not dominant. It sits in a comfortable middle ground that suits both classic and contemporary buildings, and is a common choice for mixed-use commercial developments where a clean, professional finish is required without the high reflectivity of semi-gloss.
- Good balance of aesthetics and practical durability
- Easy to clean, dirt and light marks wipe off readily
- Enhances colour depth more than matt or eggshell
- Works well across a broad range of RAL colours and building types
Semi-Gloss
Most Popular50–70 GU at 60°
Semi-gloss is the most widely specified finish for commercial aluminium window recoating, accounting for around 66% of Vanda Coatings projects. It delivers a noticeable sheen that gives metalwork a clean, well-maintained appearance, is highly practical, and suits the majority of commercial architectural contexts.
- Most durable in terms of perceived appearance over time
- Very easy to clean, resistant to dirt, environmental soiling, and surface marking
- Suits most commercial building types, offices, retail, industrial, education
- Available across the full RAL Classic and RAL Design colour ranges
Gloss / High Gloss
Declining80+ GU at 60°
High gloss finishes have the highest light reflectivity and deliver a striking, mirror-like appearance. They were more widely used in commercial metalwork historically but have declined in popularity as architectural trends have moved toward more restrained, contemporary finishes. Their main practical limitation is that they show surface imperfections, dust, and marking most readily.
- Highest light reflectivity, dramatic appearance on certain building types
- Most unforgiving of surface irregularities, minor substrate imperfections become visible
- Shows marking, fingerprints, and environmental soiling most clearly
- Can look dated on modern commercial buildings; better suited to heritage or traditional architecture
- Requires the highest standard of surface preparation to achieve an acceptable finish
Gloss level comparison for commercial exterior metalwork
| Factor | Matt | Eggshell | Satin | Semi-Gloss | Gloss |
|---|---|---|---|---|---|
| GU (60°) | <10 | 10–25 | 25–45 | 50–70 | 80+ |
| Popularity | Growing | Steady | Steady | Most popular (66%) | Declining |
| Hides imperfections | Excellent | Very good | Good | Moderate | Poor |
| Ease of cleaning | Moderate | Good | Very good | Excellent | Excellent |
| Light reflection | Very low | Low | Low–moderate | Moderate–high | Very high |
| Contemporary look | Excellent | Very good | Good | Neutral | Traditional feel |
| Preparation standard required | Forgiving | Forgiving | Standard | Standard | Very high |
Choosing the right gloss level for your project
The right gloss level depends on a combination of factors: the architectural style of the building, the substrate condition, the RAL colour being specified, and practical considerations around maintenance. Some guidance from our project experience:
Match the finish to the architecture
Contemporary commercial buildings, particularly those with dark RAL colour schemes, tend to look best with matt or eggshell finishes. The flat surface absorbs light and gives a considered, architectural quality to the metalwork. On more traditional or classical buildings, satin or semi-gloss tends to sit better, the sheen gives the frames a well-maintained appearance without looking out of place.
Consider the colour
Dark colours, RAL 9005, RAL 7016, RAL 7021, can look particularly striking in matt, and the finish helps to avoid the reflective quality that can make very dark frames appear slightly industrial at higher gloss levels. Light colours, RAL 9010, RAL 9016, RAL 7035, work well in semi-gloss, where the sheen gives the colour a clean, crisp appearance that reads well at distance.
Think about maintenance
On buildings with high footfall or those in urban environments where environmental soiling is a factor, semi-gloss offers a practical advantage, dirt and atmospheric deposits wipe off more readily than from a matt surface. If the windows are in a sheltered or less exposed location, matt or eggshell can be maintained without significant additional effort.
Substrate condition affects finish selection
Where existing substrate has minor irregularities, small dings, surface texture from previous coatings, or slight corrosion pitting, a lower gloss level is worth considering. Matt and eggshell are far more forgiving of surface variation than semi-gloss or gloss. On very well-prepared or new aluminium profiles, any finish level can be specified confidently.
When we carry out a site survey, we discuss gloss level as part of the specification conversation, considering the building type, existing coatings, substrate condition, colour selection, and client preference. There is no single correct answer, but there is usually a clearly better choice once all these factors are considered. We provide a written specification with our quotation, including the gloss level, product reference, and colour reference.
Frequently asked questions
Q
What gloss level is most popular for commercial aluminium windows?
Semi-gloss, approximately 50–70 gloss units at 60°, is consistently the most popular choice, accounting for around 66% of Vanda Coatings projects. It delivers a durable, easy-to-clean surface with a clean, professional appearance that suits the majority of commercial and residential architectural contexts.
Q
What is the difference between satin and semi-gloss on aluminium?
Satin sits at roughly 25–45 gloss units (60°), a soft, understated sheen with low light reflection. Semi-gloss sits higher at 50–70 gloss units, noticeably shinier, more light-reflective, and marginally easier to clean due to the smoother film surface. Both are excellent choices for exterior metalwork; the decision is primarily aesthetic and depends on the architectural style of the building.
Q
Does gloss level affect how long the paint lasts?
Gloss level has minimal impact on coating durability when the same 2K acrylic paint system is used throughout. The primer specification, surface preparation quality, and film thickness matter far more for long-term performance. Higher gloss finishes tend to show surface defects and UV degradation more readily over time, so they may appear to age faster visually, but the underlying chemistry and protection are the same.
Q
Is matt paint suitable for exterior aluminium windows?
Yes. Modern 2K acrylic matt finishes are fully suitable for exterior commercial use, UV-stable, weather-resistant, and durable. Matt finishes are increasingly specified on contemporary commercial buildings and work particularly well with dark RAL colour schemes. The main practical consideration is that matt surfaces can be slightly more susceptible to surface marking than semi-gloss, so cleaning with appropriate products is advisable in high-footfall locations.
Q
Can I change the gloss level when recoating existing aluminium windows?
Yes, switching gloss level on a recoat is straightforward. Moving from semi-gloss to matt, or from gloss to satin, is simply a matter of specifying the correct topcoat product. The surface preparation and priming process is the same regardless of the final finish level. Vanda Coatings can achieve any gloss level across the full RAL colour range.
Q
How is gloss level measured on paint?
Gloss is measured in gloss units (GU) using a calibrated glossmeter. The 60° measurement angle is standard for mid-range finishes. Matt finishes measure below 10–15 GU at 60°; satin is typically 25–45 GU; semi-gloss sits at 50–70 GU; high gloss is 80 GU and above. Paint manufacturers publish gloss values in their product data sheets, on commercial specifications it is worth referencing the GU range rather than relying on a label like "satin" alone, as this can vary between manufacturers.
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