Colorfastness to light testing for apparel evaluates how a specified textile color changes under a defined light-exposure method. It is useful for comparing candidate shades, lots, finishes, or suppliers against an agreed brief—not for predicting a universal number of months, seasons, or years in use. Buyer approval should lock the method, exposure, rating system, controls, and approved physical sample together.
What colorfastness to light means
Colorfastness is a textile’s resistance to unwanted color change or color transfer under a particular condition. “To light” narrows that question: will the color of this fabric, print application, trim, or finished garment change when exposed to the agreed light conditions?
The buyer concern is usually visible fading: a black becoming less deep, a saturated red losing intensity, or a pale fashion shade shifting enough to look inconsistent with the approved sample. A result can also matter when a garment combines panels, rib, sewing thread, printed artwork, embroidery, labels, or coated trims that may not change at the same rate.
A lightfastness result is not a general promise of color permanence. It is evidence tied to a particular specimen and stated method. AATCC TM16.3 describes general principles and procedures for determining textile colorfastness to light, with xenon-arc test options applicable to textile materials and to applied colorants, finishes, and treatments. Its public scope also says that using those options does not establish an accelerated test for a specific real-world application; the relationship to actual use must be agreed by the contractual parties. AATCC TM16.3
That limitation is commercially important. A display-window tee, a commuter jacket, and a garment kept mostly in a closet can each create different buyer expectations. Describe that intended context in the approval brief, but do not translate laboratory exposure into a promised retail-display duration or garment service life.
Keep lightfastness separate from adjacent color questions
A disciplined approval process avoids treating every color issue as the same test.
Initial shade matching asks whether the submitted sample matches the approved color target before exposure. It is a starting gate, not evidence of resistance to fading.
Crocking or rubbing fastness asks whether color transfers through friction. A dark denim may need a rubbing review even if its lightfastness approval is acceptable.
Wash fastness asks how laundering affects color change and staining. It should be specified separately when the care route and product use require it.
Perspiration fastness addresses exposure to perspiration, not light. Where relevant, treat it as a distinct requirement and use a separate perspiration colorfastness review rather than assuming one report answers both questions.
UV protection or UPF concerns protection from ultraviolet radiation reaching the wearer. A fading result does not demonstrate UV protection, and a lightfastness claim should never be presented as a UPF claim.
This separation helps buyers write cleaner requests and prevents a laboratory result from being applied outside its purpose.
Why method traceability matters more than a headline result
“Passed lightfastness” is too vague to approve a colorway. The meaningful record identifies what was tested, how it was exposed, how change was assessed, and what approval reference applies.
For xenon-arc work, AATCC TM16.3 publicly lists alternate light-and-dark, continuous-light/black-standard, and continuous-light/black-panel options. Those variants should be named in the request and report rather than reduced to “AATCC 16.” AATCC TM16.3
Ask for the laboratory’s stated rating system and the actual acceptance criterion selected by your brand. Do not assume that a grade from one system, exposure setting, or product category is interchangeable with another. The approval owner should be able to read the report later and understand the method version or option, exposure endpoint, specimen identity, rating basis, and disposition without reconstructing the decision from email threads.
Lightfastness is also sample-specific. A fabric development swatch, a bulk fabric lot, a garment-dyed body, and a completed decorated garment can be materially different approval objects. If the visual risk comes from a pigment print, embroidery thread, silicone badge, wash treatment, or contrast trim, decide whether the test article must include that component.
Use testing as a comparison tool, not a calendar
Buyers often ask how many test hours equal a summer, a selling season, or a year outdoors. There is no universal conversion. Q-Lab explains that outdoor conditions and test conditions vary, and frames weathering data as comparative rather than absolute service-life data. Q-Lab: hours of test exposure and outdoor exposure
For apparel approval, that points to a more useful question: compared with the approved benchmark or alternative candidate under the same agreed conditions, does this shade or construction meet the program’s requirement?
Use a comparative approach when deciding between:
- a proposed shade and an already approved shade;
- two colorant or finish routes for the same style;
- pilot material and the bulk lot intended for production;
- panel fabric, rib, print, thread, and trim within one visually coordinated garment.
This does not eliminate commercial judgment. It makes the judgment visible. A buyer can accept a deliberate fashion fade if it is described, sampled, and approved as such; the same result may be unacceptable for a core replenishment color. The criterion belongs to the product brief, not to a universal industry rule.
A decision framework for apparel buyers
Start by classifying the exposure risk and the visual consequence of color change.
Mostly indoor use
This may include garments mainly sold and stored indoors with no unusual display requirement. The buyer may still want lightfastness evidence for a sensitive shade, but the brief can stay focused on normal presentation risk. Define the garment type, colorway, fabric, finish, and approval reference.
Display-sensitive programs
For products that may spend extended time under store or window lighting, make display context explicit. State whether the concern is overall body fading, uneven panel change, logo appearance, or pack-to-display shade consistency. That context guides the acceptance brief; it does not prove equivalence between display conditions and a laboratory exposure.
Outdoor or sunlight-relevant apparel
For garments expected to see substantial daylight, lightfastness deserves earlier development attention. Review the actual colorway and any exposed embellishment or trim. Do not turn the result into a UV-protection statement or a service-life promise.
High-consequence color programs
A large tonal shift may be more damaging in black, dark navy, rich brights, contrast sets, coordinated capsules, or repeat programs where new bulk must align with retained approvals. In these cases, request lot traceability and retain a physical approved reference for future comparison.
The framework is intentionally product-led. A buyer who specifies only “high lightfastness” has not stated enough for a factory, laboratory, or internal quality team to make a defensible approval decision.
A numbered approval workflow
- Write the product exposure brief. Identify style, intended use context, sales/display context if relevant, colorway, fabric composition or construction, finish, decoration, trims, and the visual failure you are trying to prevent.
- Name the approval object. Decide whether approval applies to fabric, garment, print strike-off, trim, or complete garment. Record the shade name and code, supplier or mill reference where available, and lot or roll identity for the sample.
- Choose the method and test option before submission. State the requested standard, applicable xenon-arc option, defined exposure endpoint, rating system, and buyer acceptance requirement. Avoid shorthand that leaves the option or endpoint open to interpretation.
- Submit an unexposed control. Keep a protected, clearly labeled control from the same submitted article. It gives the approval team a direct visual reference and helps distinguish post-exposure change from ordinary batch variation.
- Review the report with the physical references. Confirm specimen identity, shade, lot, finish, method/option, exposure, rating system, and result. Compare the exposed article, unexposed control, and approved color standard under your normal review practice.
- Resolve component mismatch. If body fabric, rib, print, thread, or trim changes differently, decide whether to revise one component, approve the appearance intentionally, or request a new combined submission. Do not treat a body-fabric report as automatic approval for untested components.
- Issue a controlled disposition. Mark the submission approved, approved with a stated limitation, rejected, or pending revision. Attach the report and photographs if used, but retain the physical reference sample as the governing visual evidence where your quality system calls for it.
- Carry approval into production. Tie the approved sample, shade reference, fabric/lot details, finish, and test record to the purchase order or production file. If a material, colorant route, finish, or component changes, route it back through review rather than assuming prior approval transfers.
RFQ checklist: questions that prevent ambiguity
A good RFQ does not ask a supplier to “guarantee no fading.” It asks for a traceable proposal against the buyer’s own standard.
Include these questions:
- Which exact shade, fabric construction, finish, and garment components will be submitted?
- Is the sample from development material or the intended production lot?
- Which lightfastness method and xenon-arc option are proposed?
- What exposure endpoint, rating system, and buyer-defined acceptance criterion will govern approval?
- Will an unexposed control be retained and identified with the tested article?
- How will shade, lot, finish, and test report be linked in the production record?
- If there is a print, embroidery, wash treatment, coated trim, or contrast panel, is it included in the tested object or excluded by written agreement?
- What triggers a resubmission: a new lot, revised dye route, substituted trim, revised wash, or changed print application?
Material selection also starts before a test request. Review hand feel, construction, color direction, finishing route, and intended use together through Custom Fabrics & Materials, then convert the agreed choice into a specific approval brief.
Red flags during review
Pause approval when a report or submission has any of these gaps:
- “Pass” appears without a named method, option, exposure, rating system, or buyer criterion.
- The report identifies a generic fabric but not the submitted shade, lot, or finish.
- The buyer sees an exposed specimen but no retained unexposed control.
- A supplier uses test exposure to promise months or seasons of actual use.
- A fabric result is used to approve an untested garment dye, print, trim, or embellishment.
- A fading result is presented as evidence of UV protection or UPF.
- The approved reference cannot be located for a reorder or a color dispute.
These are documentation and scope problems, not automatic proof that the textile will fail. Resolving them before bulk approval is cheaper than debating what a vague report meant afterward.
Buyer FAQ
What are the standard guidelines for colorfastness testing?
Use a test method that matches the exposure mechanism you are evaluating, then define the specimen, conditions, rating system, and buyer acceptance requirement. For lightfastness, AATCC TM16.3 is one xenon-arc method family; the particular option and application relationship still need contractual agreement. AATCC TM16.3
How can I test fabric for colorfastness?
First define the failure mechanism. For light, submit a clearly identified textile or garment article with its shade, lot, finish, and requested method details. For washing, rubbing, or perspiration, use separate tests because they answer different questions.
Can a fabric lightfastness report approve every trim on a garment?
No. Identify what the laboratory actually tested. If the logo, rib, sewing thread or other exposed trim was absent from the specimen, keep its approval open until the agreed evidence covers it.
What does “colorfastness to light” mean?
It means resistance to color change when a textile is exposed under a defined light-testing condition. It should be read as a result for the stated specimen and procedure, not as a universal prediction of real-world lifetime.
What are non-colorfast fabrics?
In buyer terms, they are fabrics that show unacceptable color change or color transfer under the specified condition. The word is incomplete without naming that condition: light, washing, rubbing, perspiration, or another exposure route.
Move from a vague fade concern to an approvable brief
Bring the colorway, fabric or garment sample, finish details, intended use context, and any display concern into the conversation before bulk approval. JUNSHEEN can coordinate apparel development around the agreed approval record; discuss your apparel color approval brief with the specific style and shade.
