Define the spa throw before testing
A useful fastness specification starts with the article, not the test code. For this guide, the reference product is a 260gsm cotton-rich spa throw for hotel rooms, spa treatment areas, serviced apartments and wellness retail. A typical spec is 60/40 to 80/20 cotton/polyester, tolerance ±5 percentage points on declared blend unless the buyer sets tighter limits, knitted or woven face construction depending on the programme, lightly brushed or enzyme-washed handle, and 30mm polyester satin binding on four sides.
Common finished sizes are 130x170cm, 140x180cm and 150x200cm, with size tolerance often ±2cm after conditioning. For hotel use, agree shrinkage before shade approval: a practical starting target is dimensional change within -5% length and -5% width after the agreed ISO 6330 or commercial-laundry protocol, with no edge waviness that makes the throw look twisted when folded.
Binding should be specified as polyester satin, normally 75D to 150D filament yarn, colour-matched or contrast-matched to the approved standard. Sewing thread is commonly polyester 40/2 or 50/2. Labels should use wash-stable yarn, ink and backing; printed care labels and brand labels must be included in composite testing if they contact the throw during washing.
ISO 105-C06 is a controlled colour fastness to laundering test. For cotton-rich hotel spa throws, it measures colour change of the tested specimen and staining onto adjacent fibres. Colour change is graded to ISO 105-A02 and staining to ISO 105-A03. Grade 5 means no visible change; grade 1 means severe change or staining.
Do not treat ISO 105-C06 as a full hotel-laundry durability simulation. The test uses defined laboratory conditions for detergent, liquor ratio, temperature, time and mechanical action. It does not prove that a throw will survive 50-100 outsourced laundry cycles with alkali booster, oxygen bleach, high extraction, tumble drying and mixed-load contamination.
Use ISO 105-C06 as the first colour-fastness gate before bulk dyeing. Then add separate PO lines for dimensional stability, binding waviness, pilling, linting, seam appearance and commercial-laundry validation. For care-symbol alignment, see blanket care washing guidance. For inspection planning, see blanket quality control inspection points.
Specify the C06 method code correctly
The weakest PO wording is "pass ISO 105-C06". ISO 105-C06 contains several laundering conditions identified by method codes such as A1S, B1S, C1S and C2S. The letters and numbers are shorthand for defined test conditions in the standard tables, including severity, detergent system, bleaching condition where applicable, temperature, time and mechanical action. Do not paraphrase the code too loosely in a PO because buyers and suppliers may copy the wording into lab requests for years.
The suffix "S" is commonly associated with the use of steel balls for added mechanical action, but the exact temperature, duration, liquor ratio, detergent composition, bleach presence and number of balls must be taken from the selected ISO 105-C06 edition or from the accredited laboratory's controlled method sheet. If a buyer wants exact conditions in the PO, copy them from the current standard or the chosen ISO/IEC 17025 accredited lab report template, not from memory.
For practical sourcing, B1S is often used as a moderate laundering screen for controlled spa use where washing is around 50°C and oxidising bleach is not expected. C2S is a harsher gate where warmer hotel programmes or oxygen-bleach chemistry may be used. Exact conditions can vary by standard edition and lab method sheet, so the PO should require the report to state: edition year, method code, detergent system, bleach system if used, temperature, time, liquor ratio, steel-ball count, adjacent fabric type and grading standards ISO 105-A02/A03.
A PO can state: "ISO 105-C06: method B1S, tested to the laboratory's ISO/IEC 17025 accredited edition; report to include full test conditions from the standard table, including temperature, duration, liquor ratio, detergent, bleach presence or absence, number of steel balls, adjacent fabric type and individual grey-scale ratings." Use the same structure for C2S if the programme requires the harsher method.
As a buyer rule, choose B1S for white, natural, pastel and medium shades used in controlled in-house laundry with no bleach claim. Choose C2S for hotel tenders, outsourced laundry, dark saturated shades near white towels, contrast trims, or any programme where oxygen bleach may be used. If the laundry uses chlorine bleach, add a separate chlorine exposure protocol; ISO 105-C06 alone will not protect cotton from strength loss, yellowing or localised damage.
Choose multifibre adjacent fabric deliberately
Require ISO multifibre adjacent fabric and report the staining grade on every individual strip. Do not accept only "pass" or an averaged composite grade. Pass/fail should be based on the lowest fibre staining grade because one failing strip may represent a real hotel risk, such as transfer to white cotton towels or polyamide spa uniforms.
Multifibre DW and TV are both seen in buyer manuals, but they are not interchangeable for approval unless the buyer accepts equivalence. DW is often selected for broad cellulosic and synthetic risk coverage, including cotton, polyamide, polyester, acrylic and wool-type staining behaviour. TV may be specified by certain retailers, regional manuals or lab scopes where its fibre combination is the controlled reference.
The PO should state one adjacent fabric type: "Use ISO multifibre adjacent fabric type DW" or "Use ISO multifibre adjacent fabric type TV". Align this with the retailer manual, hotel brand standard and the selected lab's ISO/IEC 17025 accreditation scope. Do not approve lab dips on DW and bulk on TV unless the buyer has reviewed the difference and accepted the comparison risk.
For satin-bound spa throws, add a second composite contact check: body fabric against binding, binding against body, sewing thread across both sides, and label in its real sewn position if it can bleed or crock. Fabric-only testing misses the common failure: a clean body with a grey edge, dark thread halo, label bleed, or contrast binding migration.
Use shade-family pass grades
A single pass grade for every shade is easy to write but weak for sourcing. White and cream have yellowing and greying risk; dark navy and burgundy have unfixed dye risk; contrast binding has cross-staining risk. Use a shade-family table so concessions are visible before bulk dyeing.
| Shade or component | Suggested C06 method | Colour change | Staining requirement | Buyer action |
|---|---|---|---|---|
| White / natural / undyed | B1S; C2S if oxygen bleach may be used | ≥4-5 preferred; no visible greying or yellowing | ≥4-5 on every adjacent strip | Review whiteness and yellowing under D65 and TL84 |
| Pastel shades: ivory, mist grey, pale sage | B1S minimum; C2S for outsourced laundry | ≥4 | ≥4 on every adjacent strip | Check label, thread and binding staining separately |
| Medium shades: taupe, stone, olive, mid grey | B1S or C2S depending on laundry | ≥4 | ≥4 on every adjacent strip | Approve washed PPS, not only lab dip |
| Dark / saturated: navy, black, forest, burgundy | C2S for hotel risk; B1S only by written concession | ≥4 target; ≥3-4 only by written shade concession | ≥4 on every adjacent strip; no concession near white linen | Require extra soaping or recipe change if staining drops below 4 |
| Contrast satin binding | Same as body shade; test as sewn composite | ≥4 for binding appearance | ≥4 against body and adjacent fabric | Test body-to-binding and binding-to-body staining |
| Label / embroidery / thread | Same method as full article | No visible bleeding, halo or shade break | ≥4 on adjacent fabric and contacted body area | Change thread, label ink or backing if staining appears |
Colour change grade 3-4 on a dark saturated shade may be commercially acceptable only if the washed specimen still matches the approved tolerance and the buyer signs a shade-specific concession. Do not concede staining below grade 4 if the throw will touch white robes, towels, sheets, spa uniforms or pale upholstery.
For dark cotton-rich shades, ask the dyehouse how they control unfixed reactive dye: scouring, salt and alkali dosing, pH after neutralisation, soaping temperature, rinse conductivity target and machine loading. A low-cost recipe can pass on a lab dip and fail in bulk if soaping time is cut or the bath is overloaded.
For white and natural throws, fastness is not the whole problem. Add visual checks for greying, yellowing, optical brightener mismatch and dull satin edges after wash. A white cotton-rich body with a yellow-cast polyester satin binding can pass staining grades and still fail hotel room inspection.
Control edge-specific failures
Satin binding is usually the first component to look wrong after laundering. Polyester satin may keep strength but change visual tone because its smooth surface reflects light differently from the cotton-rich body. It may also pucker if the body shrinks more than the binding, if sewing tension is too high, or if the binding is fed under uneven tension.
Add measurable edge tolerances to the PO. A practical starting point for a 260gsm spa throw is finished satin binding width 30mm ±2mm before wash and width change within ±2mm after the agreed wash. Edge waviness should not exceed 5mm over any 300mm measured length after conditioning. Corners should sit flat without rope-like edges, tunnelling, exposed raw edges or visible twist.
| Failure | Acceptance criterion after laundering | Likely control point |
|---|---|---|
| Satin binding puckering | Minor only; no rope edge, no tunnelling, no corner twist | Body shrinkage balance, binding feed, sewing tension |
| Greyying or yellowing | No visible edge/body tone break under D65; colour change ≥4 unless stricter shade rule applies | Detergent compatibility, optical brightener, fibre blend, drying heat |
| Edge waviness | ≤5mm wave height over 300mm after conditioning | Differential shrinkage, over-stretched binding, unrelaxed fabric |
| Thread haloing | No coloured halo along seam; staining ≥4 on contacted body area | Thread dye, lubricant, shade selection, needle heat |
| Label bleed | No ink transfer, no backing stain, no local halo; staining ≥4 | Label ink, heat transfer film, care-label substrate |
Stitch construction should be defined. For satin-bound spa throws, 8-10 stitches per inch is a common working range, but the final setting depends on fabric density and binding thickness. Require no skipped stitches over 100mm, no broken seam, no exposed raw edge, no binding roll-off at corners, and secured seam ends where the construction needs it.
Thread can pass washing but still look poor. Polyester 40/2 or 50/2 is common, but lubricant, shade mismatch or excessive tension can show as dotted lines after wash. Include thread in the composite ISO 105-C06 specimen and in the washed appearance review.
Sampling and retained specimens
Test at five control points. First, test the lab dip or strike-off for each colour before colour approval. Second, test the sewn pre-production sample with actual binding, thread and label. Third, test the first bulk lot before shipment release. Fourth, test each dye lot or colour lot when bulk is split across machines, dates or dye batches. Fifth, retest whenever binding, sewing thread, label supplier, dye recipe, finishing route or laundry claim changes.
For continuous programmes, a practical control is one accredited lab test per colour per bulk dye lot, plus one retained counter sample from every production lot. If a hotel or retailer has a stricter manual, follow that manual. Do not combine different colour lots under one report unless the report identifies every specimen and the buyer has approved reduced testing.
Require ISO/IEC 17025 accredited lab reports for the chosen ISO 105-C06 method. The report should include sample description, colour name, colour lot or dye lot, component list, specimen construction, adjacent fabric type, method code, edition year, test conditions, grey-scale ratings for colour change and each staining strip, photographs before and after test, and any deviations.
Retain sealed specimens. Keep one signed pre-production sample at the mill and one with the buyer. For bulk, retain at least one unwashed and one washed sample per colour lot until the claim window closes. Label each retained specimen with PO, style, colour, dye lot, roll or batch, binding lot, thread lot, label lot, test date and wash method.
For inspection sampling, align lab testing with final AQL. A typical soft-goods final inspection may use ANSI/ASQ Z1.4 or ISO 2859-1, general inspection level II, AQL 2.5 for major defects and 4.0 for minor defects, unless the buyer manual states otherwise. Lab failures should block release regardless of visual AQL pass unless the buyer signs a concession.
PO-ready ISO 105-C06 clause
Use wording that a supplier, lab and inspector can execute without interpretation. The clause below is intentionally complete; delete only the parts that are not relevant to the programme.
Colour fastness to laundering: test finished sewn composite specimens to ISO 105-C06, method [B1S/C2S], tested to the selected laboratory's ISO/IEC 17025 accredited edition. Lab report must state edition year, method code, temperature, duration, liquor ratio, detergent system, bleach presence or absence, steel-ball count, adjacent fabric type [DW/TV], specimen construction, and grading standards ISO 105-A02 for colour change and ISO 105-A03 for staining. Specimen shall include body fabric, satin binding, sewing thread and any label or decoration that can contact the article in laundering. Report colour change and staining grade for each component and each individual multifibre strip; pass/fail is based on the lowest fibre staining grade, not an average. Shade requirements: white/natural colour change ≥4-5 and staining ≥4-5; pastel, medium and contrast components colour change ≥4 and staining ≥4; dark/saturated colour change ≥4 target, with ≥3-4 allowed only by written buyer concession; staining below ≥4 is not accepted for hotel use near white linen. Test one sample per colour per bulk dye lot and retest if dye recipe, dye lot, finishing route, binding, thread, label, decoration or laundry claim changes. Retain one unwashed and one washed specimen per colour lot with PO, colour, dye lot and component lot identification. Concession authority rests only with [named buyer role], not factory QC, agent or freight forwarder.
Add a release rule: "Shipment cannot be booked until the buyer receives the accredited report, pre/post-test photos, retained specimen IDs and mill QC confirmation that bulk shade, binding, thread and label match the tested specimen." This prevents a lab-pass fabric from being shipped with substituted trim.
Commercial-laundry validation protocol
ISO 105-C06 is a laboratory screen. Hotel approval needs a separate wash-and-wear validation using the actual or worst-case laundry process. Run this before bulk cutting if the hotel has strict appearance standards or outsourced laundry.
| Protocol item | Suggested control | Pass/fail focus |
|---|---|---|
| Cycle count | 10 cycles for pre-approval; 25 cycles for higher confidence; 50 cycles for long-term tender validation where timing allows | Progressive shade loss, edge distortion, linting |
| Wash chemistry | Record detergent, alkali booster, oxygen bleach, neutraliser and softener; prohibit chlorine unless separately approved | Yellowing, greying, fibre damage, dye bleed |
| Temperature | Use hotel process, often 40-60°C; validate higher temperature if laundry may sort incorrectly | Differential shrinkage and binding puckering |
| Load type | Wash with representative towels/robes or ballast; include white cotton witness cloths for dark shades | Cross-staining and lint transfer |
| Drying | Record tumble temperature, time and cool-down; compare line or flat drying only if used commercially | Overdrying, heat glazing, satin dulling, shrinkage |
| Assessment | Inspect after conditioning under D65 and TL84; measure size to ISO 5077 if using ISO 6330 pre-wash procedure | Dimensional change, twist, binding waviness, appearance |
A practical pass target after 10 commercial cycles is: no guest-visible staining or label bleed; no edge waviness above 5mm over 300mm; no binding width change beyond ±2mm; no seam failure; no unacceptable lint on white witness fabric; dimensional change within the agreed tolerance; colour remains commercially matched to the approved washed standard.
For 25 or 50 cycles, accept that cotton-rich fabric will soften and may lose some depth. The decision should be based on the approved washed standard, not the unwashed salesman sample. If a hotel wants a crisp retail appearance after many industrial cycles, the buyer may need a different construction, darker tolerance standard, or heavier binding.
Risk matrix by shade and component
| Risk area | Likely root cause | Corrective action before bulk |
|---|---|---|
| Dark navy or burgundy body stains adjacent fabric | Insufficient soaping, poor rinse conductivity control, overloaded dye machine | Increase soaping time/temperature, adjust dye recipe, retest C2S on bulk strike-off |
| Dark sewing thread leaves seam halo | Incompatible thread dye or lubricant migration | Change thread supplier or shade, wash-test thread with body and binding before PPS |
| Printed label bleeds onto pale body | Label ink or backing not stable to detergent/heat | Switch to woven label, heat-set ink system, or relocate label away from contact area |
| White body looks grey but staining grades pass | Polyester optical mismatch, redeposition, mixed-load contamination | Align optical brightener, change binding tone, improve rinse, validate with white witness cloth |
| Satin edge yellows or looks glazed | Overdrying, excessive tumble heat, finish incompatibility | Lower drying temperature, add cool-down, change binding finish, test commercial cycles |
| Binding puckers after wash | Differential shrinkage, tight stitch tension, stretched binding feed | Pre-relax body fabric, adjust feed ratio, reduce thread tension, recheck after laundering |
The root cause is often a component mismatch rather than a bad body fabric. Do not approve body-yardage lab results and then buy binding, labels or thread from another source without a new composite wash test.
Supplier questionnaire for dyehouse control
Ask these questions before approving the colour route. The answers are more useful than a generic promise that the fabric is "colourfast".
- Which dye class is used for the cotton portion and which colourant is used for the polyester portion, if applicable?
- What are the target pH, soaping temperature, soaping time and final rinse conductivity for dark shades?
- Is the same recipe used for lab dip, strike-off and bulk, or are there machine-scale changes?
- What is the maximum dye-machine loading ratio for this 260gsm construction?
- Are binding, sewing thread and labels sourced from approved lots before PPS testing?
- Does the mill keep retained washed and unwashed specimens by colour lot and component lot?
- Which accredited lab is used, and is ISO 105-C06 with the chosen method and adjacent fabric inside its ISO/IEC 17025 scope?
- What corrective actions are triggered if staining is grade 3-4 or lower on any multifibre strip?
If a supplier cannot answer these questions, reduce risk by testing more colour lots, approving only washed PPS, and blocking trim substitution after approval.
Concession decision tree
Concessions should be rare and written. Use a simple decision tree so commercial pressure does not override hotel-use risk.
- If staining is below grade 4 on any adjacent strip, reject for hotel use near white linen; do not ship unless the buyer changes the use case.
- If colour change is grade 3-4 on a dark shade but staining is ≥4, compare with the approved washed standard; buyer may concede only if appearance remains acceptable.
- If white, natural or pastel shades show visible greying or yellowing, reject or rework even if grey-scale numbers look passable.
- If binding puckers, waves or bleeds while body fabric passes, reject the component combination and retest with revised binding/thread.
- If the lab report lacks method code, adjacent fabric type, individual strip grades or specimen identification, treat it as incomplete and do not release shipment.
- If a concession is granted, record shade, lot, defect, customer-use limitation, expiry date and named buyer authority.
Factory QC, agents and logistics teams should not grant concessions on wash fastness. Authority should sit with the buyer's technical manager, hotel textile manager or nominated quality lead.
Pre-shipment release checklist
Use this checklist before booking the container or handing goods to the forwarder.
- Accredited ISO 105-C06 report received for each required colour lot and method code.
- Report states ISO edition, B1S or C2S, full test conditions, DW or TV adjacent fabric, ISO 105-A02/A03 grading and individual strip staining grades.
- Composite specimen includes body fabric, satin binding, sewing thread and label or decoration.
- Bulk binding, thread, label and body fabric lots match the tested PPS or approved bulk specimen.
- Commercial-laundry validation completed where hotel or outsourced laundry risk applies.
- Final inspection checks edge waviness, puckering, greying, thread haloing, label bleed, linting, shade and folded appearance.
- Retained unwashed and washed specimens are sealed and labelled by PO, colour, dye lot and component lots.
- Any concession is signed by the named buyer authority before shipment release.
For programmes using recycled polyester, organic cotton, special finishes or retailer chemical manuals, colour fastness must sit alongside chemical and claim documentation. For broader claim planning, see textile certifications explained for buyers and sustainable recycled blanket sourcing.
Frequently asked
Is ISO 105-C06 enough for hotel spa throws? No. ISO 105-C06 is a controlled laboratory wash-fastness screen. Hotel spa throws also need commercial-laundry validation for repeated cycles, detergent chemistry, drying heat, dimensional change, binding waviness, linting and appearance.
Should buyers specify B1S or C2S? B1S is a practical moderate screen for controlled laundry without oxidising bleach. C2S is safer for hotel tenders, outsourced laundry, dark shades, contrast trims or possible oxygen-bleach exposure. The PO should copy exact conditions from the selected standard edition or accredited lab method sheet.
What staining grade is acceptable for dark cotton-rich spa throws? For hotel use near white linen, require staining grade ≥4 on every individual adjacent fabric strip. Slight colour change on a dark shade may be conceded in writing, but staining below grade 4 is a high guest-claim risk.
Why test the satin binding with the body fabric? Binding, body fabric, thread and labels shrink, reflect light and release colour differently. A body-only test can pass while the sewn throw fails through edge greying, puckering, thread haloing or label bleed.
Which adjacent fabric should be used, DW or TV? Use the type required by the retailer, hotel manual or accredited lab scope. DW is often used for broad fibre staining coverage; TV may be required by specific manuals or markets. State one type in the PO and do not mix types between lab dip and bulk approval without buyer sign-off.
What records should be retained after testing? Keep the ISO/IEC 17025 accredited lab report, grey-scale ratings, pre/post-test photos, specimen IDs, colour lot and component lot records, and sealed washed and unwashed retained samples until the claim window closes.
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