Material selection
Colour matching acrylic: why the same colour looks different on two parts
Colour is judged by eye, in a light you did not choose, against something you remember. A process beats a promise.
Material selection
Colour is judged by eye, in a light you did not choose, against something you remember. A process beats a promise.
Coloured acrylic comes in two forms: a pigmented sheet, where the colour is in the material, and a clear sheet painted or printed on the back. They behave differently in matching, in depth and in how they age, and much of the frustration around colour comes from not deciding which one was wanted.
| Pigmented / tinted sheet | Painted or printed back | |
|---|---|---|
| Appearance | Colour in the body, depth, translucent glow | Flat, opaque, exact colour |
| Colour accuracy | Nearest sheet colour, close but not exact | Exact Pantone or RAL match |
| Edge colour | Same colour all through | Clear edge, contrast at the edge |
| Batch variation | Yes, batch to batch | Minimal if the same ink and process |
| Scratch visibility | Scratches less visible in a dark tint | A scratch on the clear face shows |
| Cost | Sheet dependent | Print plus a clear panel |
| Best for | Design intent where the material colour is the point | Brand colour that must be exact |
Cast acrylic is polymerised in batches, and each batch of pigment dispersion sits slightly differently. Two batches of the same nominal colour will be very close but not identical, and the difference is visible when the parts are placed side by side. This is normal, it is within the sheet manufacturer's tolerance, and no fabricator can eliminate it in cast sheet.
What can be controlled is the process around it:
The same panel reads warm under tungsten, cool under LED, and greener under fluorescent light. A colour approved in a showroom with warm lighting can look wrong in a store lit with cool white LED. This is not a manufacturing issue, it is metamerism, and it affects painted surfaces as much as tinted sheet.
The practical rule: approve the swatch under the lighting the part will actually be seen in. If the part will be seen in several environments, approve it in daylight (D65) and accept that it will shift in the others.
For an exact brand match, the reliable routes are:
A fabricator who promises an exact Pantone match in a tinted sheet is either using a printed back or overstating what the material can do.
A tinted sheet carries the colour to the edge, so a polished edge glows in the same hue. A clear panel with a printed back has a clear edge, which creates a bright line around the part. In a display this can be a design feature or a distraction. Decide which before the part is made, because it cannot be changed afterwards without remaking it.
Three sentences in a purchase order prevent most colour disputes:
Colour: [swatch reference], approved sample retained by both parties.Judged in daylight D65 against the retained swatch.Batch variation within the sheet manufacturer's tolerance is accepted.What none of this solves is a customer who approved one colour and now wants another after seeing the parts. That is a change, not a claim, and it is quoted as one — which is why the physical swatch is worth the two days it takes.
In a printed back, very close. In a tinted sheet, you get the nearest available colour, which is usually close but visibly different side by side. Exact matches in tinted sheet require a custom batch and a large minimum quantity.
Gloss level, pigment dispersion and light all affect it. Black is the most consistent colour, so a visible difference usually means a change in finish rather than the colour itself. Compare the same face at the same angle.
A stock sheet colour can be a chip cut from stock in a day or two. A printed back needs a printed sample, which is 3 to 5 business days. Both are worth waiting for before a rollout.
Good quality pigmented acrylic holds colour well, but saturated reds and blues are the most vulnerable over many years. A printed back with a UV-resistant ink behind a clear panel resists fading better because the ink is protected.
Yes, and it is the best brief you can give us. Send the part; we will compare against the sheet range under daylight and tell you how close we can get, and whether a printed back would be closer.
Tell us the colour reference and where the part will be seen, and we will send a physical chip for approval in the light that matters.