Colour Transfer from PU Shoe Linings: What to Check Before Changing the Material

This guide helps footwear buyers and product developers prepare that investigation. It provides a sample-checking framework, not a diagnosis of a particular shoe or a universal pass requirement for polyurethane (PU) linings.

Start with the stained part and the timing

Keep the affected shoe or assembly, the stained sock or component if available, and an unused reference from the same material batch. Before cleaning or cutting anything, photograph the stain, the corresponding lining area and the contact arrangement. Label the suspected colour source and the material receiving the mark separately; either identification may need to change after testing.

Record these details in one investigation note:

• Shoe style and component: heel lining, collar, tongue, insock or another part; identify which material face contacts the sock or neighbouring component.
• Material article, colour reference and batch or roll identifier for each relevant part, including the stained recipient when known.
• First observation: during assembly, unpacking, storage, fitting or wear; distinguish known facts from a customer’s estimate.
• Conditions: dry or damp, any reported perspiration or cleaning exposure, approximate contact duration and storage history. Mark unknown details as unknown.
• Surface condition: intact, polished, scratched, peeling or visibly losing particles; record the stain on the other material separately.

These records are a practical way to brief the supplier and laboratory. They do not, by themselves, identify a chemical mechanism. If the broader lining specification is still undecided, first use the PU shoe lining selection guide to define the component and construction.

If the mark follows rubbing contact

Colour transferred during repeated movement is one possibility when staining corresponds to a contact area. Ask the laboratory whether dry and wet rubbing assessments suit the material and complaint. SATRA TM167 assesses transfer from a coloured surface during mild rubbing, using an undyed cotton cloth as the receiving material. Its listed applications include synthetic uppers and linings. SATRA TM167 scope and principle

Keep the dry and wet results distinct and ask which surface was tested. For TM167, distinguish its cloth-staining assessment from any separately requested observation of the lining surface. A hand rub may help locate an area worth investigating, but undocumented pressure, moisture and rubbing duration cannot support a claim that a standard has been passed.

A result obtained against a specified test cloth also needs context when the complaint concerns a particular sock or a different light-coloured component. Ask the laboratory how to investigate that actual pairing alongside the appropriate standard test, and identify any additional comparison as a separate trial.

If moisture is involved

A stain reported after damp wear raises a different question: could colour bleed under the relevant moisture exposure? SATRA TM335 covers bleeding associated with water or perspiration and uses a standard multifibre fabric. Its public description separates water, alkaline artificial-perspiration and acid artificial-perspiration procedures. A water result therefore should not be relabelled as a perspiration result. SATRA TM335 scope and principle

Tell the laboratory what is known about the exposure and ask which procedure fits the investigation. Do not improvise a perspiration solution or select a temperature and duration from an unrelated report. The method, conditioning, assessment and buyer’s acceptance criteria need to be agreed before interpreting the result.

Moisture and movement may both have occurred in wear. Keep the questions separate enough to learn something: whether colour transfers under the chosen rubbing conditions, and whether bleeding occurs under the selected moisture conditions. Neither finding alone establishes every cause of the reported stain.

If the lining surface is damaged

Inspect the lining as well as the stained item. Peeling, loss of coating or visible debris makes surface integrity another part of the investigation. Avoid describing every visible mark as dye bleeding, or assuming that staining proves the lining has worn through.

SATRA distinguishes assessments of surface damage from assessments of transfer onto other materials. Its discussion of abrasion and rub testing also shows why the test must suit the intended application. Ask the laboratory which examination or abrasion assessment is appropriate for the observed damage, rather than substituting the most severe available test. SATRA on rub, abrasion and scuff resistance

Request separate observations for damage to the donor surface and staining of the receiving material. SATRA describes different grey scales for colour change and staining; a report should make clear what its rating evaluates. SATRA on colour fastness and rub testing

If staining appears during storage or before wear

When an unworn shoe or packed assembly is already marked, document what touched the affected area. Preserve the adjacent material and note whether an adhesive was present. The investigation may need to address contact between components rather than only movement against a sock.

SATRA TM343 examines whether close contact during storage can cause one material to discolour another, including materials bonded with adhesives. Its principle includes comparison with unexposed references. This makes contact-storage assessment a relevant question for the laboratory when the timing and contact pattern point in that direction. SATRA TM343 scope and principle

A pre-wear stain is not proof that the lining caused it. Ask for the actual suspected pair to be considered, and document how its assembly differs from an unbonded material sample. Keep the original assembly available until the laboratory has advised which specimens it needs.

Keep light and dark materials separate before assembly

As a practical precaution against contact staining, store light-coloured and dark-coloured materials separately. Do not stack, fold or pack them together with their surfaces touching. Apply the same separation to loose swatches and cut components while they await assembly. This recommendation follows the contact-risk principle described in SATRA TM343; it is not a claim that the method prescribes a particular storage system. SATRA TM343 scope and principle

Separation reduces the opportunity for direct-contact staining during handling and storage. It does not establish rubbing or perspiration colourfastness, or guarantee that all colour transfer will be prevented. Where light and dark components must touch in the finished shoe, assess that actual combination under the agreed conditions before approval.

Choose a test question before choosing a replacement

A useful request is specific: “Please assess transfer from this lining face under the agreed rubbing conditions,” or “Please investigate discolouration between these two components after contact storage.” A general request to “test colourfastness” leaves important choices unresolved.

ISO 17700:2019 illustrates the distinction: its public abstract identifies three methods for dry or wet rubbing transfer and a separate bleeding method, applicable to footwear uppers, linings and insocks irrespective of material. A reference to the standard alone does not identify which method was used. ISO 17700:2019 abstract

Before commissioning work, agree the specimen identity, method and edition, exposure or conditioning, result to be assessed, and acceptance criteria for the intended shoe. Where an investigative trial departs from a standard, ask for that departure to be identified. This article cites public method descriptions; it does not reproduce the full methods or prescribe their operating settings.

Arrange special colourfastness requirements before ordering

For Youxiang Leather orders, special colourfastness requirements need a custom arrangement. State them at the enquiry stage so feasibility, sample preparation and testing can be confirmed before the order. Do not assume that a standard article already meets every requested colourfastness grade.

Provide the intended shoe component and use, the exact article and colour, the receiving material, the test method and edition, the test conditions and the target rating or other acceptance criteria. Agree the requirements first, then assess the customised sample and intended assembly. A custom arrangement is not a guarantee of a particular result; approval still depends on the agreed sample verification.

Validate the proposed change in the intended assembly

If a supplier proposes a different finish, colour, backing or complete article, record exactly what changed. Avoid approving a replacement solely because it belongs to a different material category or looks similar to the reference.

Use the following sequence as a purchasing check:

1. Preserve the original evidence and identify the current article, colour and batch. Keep unused reference specimens wherever available.
2. Record the proposed corrective change and the reason for trying it. Treat that explanation as a hypothesis until the comparison supports it.
3. Compare the original and proposed samples under the same agreed conditions. If conditions differ, keep the results separate and explain why.
4. Check the proposed material with the intended neighbouring components and assembly process. A satisfactory result for an isolated specimen does not settle an unresolved complaint about a bonded or contacting pair.
5. Review both the receiving material and the lining surface. Record the test findings, remaining uncertainty and the buyer’s decision against the agreed criteria.
6. Tie approval to the specific sample and construction. Reconfirm the scope of approval if the article, colour, finish or assembly changes.

Matching the required shade remains a separate approval task; use physical colour samples for appearance comparison. A colour match does not establish transfer resistance.

Youxiang Leather is a footwear-material trading company. To discuss candidate samples, use material matching and include the component, material references, observed stain, exposure history and required tests. Any proposed sample should be assessed against the buyer’s requirements before order approval.

What this guide cannot establish

The checks above do not diagnose a stain from a photograph, certify a material, or demonstrate that any Youxiang article has passed a test. No customer case, laboratory result or universal pass grade is claimed here. The appropriate method and acceptance criteria depend on the product and agreed requirements; consult the laboratory’s current full method before testing.

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