How to Read a Textile Test Report
GSM, colour fastness, shrinkage, pH, and AQL — a complete guide to interpreting lab test reports for towels and bed linen procurement
Step 1: Identify the Testing Laboratory
Verify the lab is accredited
A textile test report is only as credible as the laboratory that issued it. Check that the lab holds ILAC (International Laboratory Accreditation Cooperation) accreditation — in practice this means ISO/IEC 17025 accreditation from a national accreditation body (NABL in India, UKAS in the UK, A2LA in the USA, DAkkS in Germany). Major accredited labs for Indian textile exports include SGS India, Intertek Testing Services India, Bureau Veritas Consumer Products Testing, TÜV Rheinland India, and NABL-accredited labs such as SITRA (South India Textile Research Association).
Check the report header
The test report header should state: laboratory name and address, report number and date, test method references (e.g. ISO 105-C06), sample description submitted by the client, and the accreditation logo with accreditation certificate number. Any report missing these elements — or showing a lab you cannot verify on the ILAC MRA database — should be treated with caution.
Step 2: Check Sample Description Matches Your Specification
Sample identity section
The report will describe the sample submitted for testing: product type (e.g. "100% cotton terry towel"), colour, weight per square metre (GSM), size, and possibly a batch or style reference. Verify this description matches the product you specified. A common fraud is submitting a higher-quality sample for testing than the bulk production run. Cross-reference the report date against the production timeline — a report dated before your PP sample approval is suspicious.
Who submitted the sample
The report will show who submitted the sample to the lab — ideally it should be submitted by the supplier or by a third-party inspector you commissioned. If a report is submitted in your name but you never instructed the lab, this is a red flag. Request that any test reports on production samples be submitted directly by an independent third-party inspection agency rather than by the supplier.
Step 3: Read GSM Result vs Tolerance
Understanding the GSM result
GSM (grams per square metre) is tested by weighing a precisely cut fabric specimen. The test method is ISO 3801 or ASTM D3776. The report will show: the method used, the individual specimen weights, and the mean GSM result. Compare the reported GSM to your specification with its tolerance (e.g. "550 GSM ± 25 g/m²"). A result of 525–575 GSM is within tolerance; below 525 or above 575 is out of tolerance.
Common GSM failure modes
Two common GSM failures: (1) Underweight: the product is lighter than specified, meaning less cotton content — the most common compromise in unethical production. (2) Overweight: less common, but excess weight adds cost without proportional benefit in performance. A single borderline GSM result is not necessarily a rejection — check whether it falls outside the stated tolerance and whether it is consistently low across multiple specimens.
Step 4: Interpret Colour Fastness Grades
The ISO 105 grading scale
Colour fastness is graded on a scale of 1 to 5 where: Grade 1 = very poor (significant colour change or staining), Grade 3 = moderate (acceptable for some applications), Grade 4 = good (acceptable for most hospitality applications), Grade 5 = excellent (no perceptible change). For hotel and hospitality linen, minimum acceptable grades are: colour change Grade 4, staining Grade 3–4.
Common colour fastness tests in textile reports
Reports for hospitality linen typically include: • ISO 105-C06: Colour fastness to domestic and commercial laundering — the most important test for hotel use. Tests how the colour holds after machine washing at 40°C or 60°C. • ISO 105-X12: Colour fastness to rubbing (crocking) — dry and wet rubbing. Important for dyed towels and coloured bed linen. • ISO 105-B02: Colour fastness to artificial light (xenon arc). Important for linen stored near windows. • ISO 105-E04: Colour fastness to perspiration.
Step 5: Check Shrinkage Percentages
Reading shrinkage results
Shrinkage is tested per ISO 6330 (domestic washing) or ISO 3175 (dry cleaning). The report shows percentage dimensional change in both warp (lengthwise) and weft (widthwise) directions after 1, 3, or 5 wash cycles. Negative values indicate shrinkage (the fabric became smaller); positive values indicate extension (fabric grew). Standard acceptable shrinkage tolerances for linen: • Towels: ≤5% in both directions after 3 washes • Bed sheets: ≤3% in both directions after 3 washes • Fitted sheets: ≤4% (extra tolerance for stretch during fitting)
What excessive shrinkage means
If a bath towel specification states 70×140 cm finished dimensions but the report shows 6% warp shrinkage, the actual towel after customer washing will be approximately 65×140 cm — meaningfully smaller than specified. Excessive shrinkage is often caused by: insufficient pre-washing during finishing, incorrect preshrinking treatment, or underweight fabric where the manufacturer cut corners on pre-treatment cost.
Step 6: Review pH Level
Why pH matters for skin contact textiles
Human skin has a pH of approximately 5.5 (mildly acidic). Textiles with an alkaline pH (above 8) can cause skin irritation, particularly in sensitive skin consumers and infants. Dyeing and finishing processes use alkaline chemicals (caustic soda, sodium carbonate) that must be thoroughly washed out. OEKO-TEX STANDARD 100 requires textiles for direct skin contact to have a pH between 4.0 and 7.5.
Interpreting pH test results
pH is tested per ISO 3071. The report will show the pH value measured in aqueous extract. Acceptable range: 4.5–7.5 for hotel towels and bed linen. A pH above 8 indicates alkaline residues from dyeing — this fails OEKO-TEX compliance and should trigger a CAR requiring the supplier to address their finishing wash process. A pH below 4 indicates acidic treatment residues from finishing, equally problematic.
Step 7: Read AQL Defect Rates
Understanding AQL in an inspection report
AQL (Acceptance Quality Limit) inspection reports are separate from laboratory test reports but often provided alongside them. An AQL 2.5 inspection report (per ISO 2859-1) shows: the lot size (total pieces in the batch), the sample size inspected (determined by the AQL table), the number of defects found (categorised as Critical, Major, Minor), and the Accept/Reject decision. For AQL 2.5 at Inspection Level II, a 5,000-piece lot requires 200 pieces inspected; if more than 14 Major defects are found, the lot is rejected.
Common defects in textile inspection reports
Major defects (causing rejection if too many are found): holes, severe weaving faults, broken loops (towels), running stitches, major colour variance, significant size deviation outside tolerance, incorrect labels. Minor defects (acceptable up to a higher threshold): slight colour shading (within tolerance), minor uneven pile (isolated), loose thread not affecting integrity, minor label misprint. A comprehensive inspection report lists each defect by type, location, and severity classification.
Frequently Asked Questions
Which testing labs are accredited for Indian textile exports?
Major NABL/ISO 17025-accredited labs for Indian textile testing include: SITRA (South India Textile Research Association, Coimbatore), SGS India (multiple locations), Intertek Testing Services India (Mumbai, Tirupur, Delhi), Bureau Veritas India, TÜV Rheinland India, and SGS Karur for terry towel exporters. For OEKO-TEX certification, only OEKO-TEX member institutes can issue certificates; HOHENSTEIN (Germany) is the most common for Indian manufacturers.
What are acceptable tolerances for GSM, colour fastness, and shrinkage?
Standard acceptable tolerances: GSM ±5% of specification (so 550 GSM ±27.5 g/m²). Colour fastness: minimum Grade 4 for colour change, Grade 3–4 for staining on ISO 105-C06 washing test. Shrinkage: ≤5% for towels, ≤3% for bed sheets after 3 wash cycles. pH: 4.5–7.5 for skin-contact textiles. These tolerances align with OEKO-TEX STANDARD 100 requirements and typical hotel procurement specifications.
How do I know if a test report has passed or failed?
Look for the pass/fail statement at the end of each test section, or a summary results table. A "Conforming" or "Pass" result means the specimen met the specified requirement. "Non-Conforming" or "Fail" means it did not. If the report only shows measured values without a pass/fail statement, compare each result to your specification tolerance manually. Any result outside your stated tolerance is a failure regardless of how the report characterises it.
What should I do if a test report shows a failure?
Issue a Corrective Action Request (CAR) to the supplier immediately. Specify which test failed, the result obtained, the required standard, and your deadline for a corrective action response. The supplier should investigate root cause (yarn quality, dyeing process, finishing inadequacy), implement a fix, produce a new sample, and submit it to the same accredited lab for re-testing. Do not accept goods shipped without a passing test report for the specific production batch.
What is the pH requirement for hotel towels?
For hotel towels supplied for skin-contact use, the pH of the finished textile should be between 4.5 and 7.5 — mildly acidic to neutral. This is the OEKO-TEX STANDARD 100 requirement for products in direct contact with skin. A pH outside this range is a certification non-compliance and may cause skin irritation complaints. Testing method: ISO 3071 (pH of aqueous extract of textiles).
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