Every wiper supplier has a test report. Very few buyers read past the summary table. That is understandable — the documents are dense, the units vary, and the methods are not always named. It is also where most of the risk sits.
A number without a method is a rumour. Here is how to read the three sections that decide whether a reported value is evidence or decoration.
Section one: the method
Particle and fibre release from wipers is usually assessed against IEST-RP-CC004, which describes several test approaches including biaxial shake, wet and dry. The method determines the answer, so a report that says "particle count: 1,200" without naming the method is not comparable to anything.
Ask three questions of any method statement. Was the sample handled in a cleanroom? Was the liquid particle counter calibrated? Was the result reported per square metre, per wipe, or per test volume? A count per wipe means nothing if the wipe size changed between lots.
Section two: sample preparation
This is the quiet separator between good and bad data. A sample cut in a normal laboratory, handled with bare hands and tested within the hour will produce a different result from one cut in a cleanroom, bagged, and equilibrated.
Look for statements about gloves, tweezers, bagging and equilibration time. If they are absent, assume the sample was handled conventionally and discount the number accordingly.
A report with a detection limit higher than the specification it claims to meet. If the limit of detection is 500 particles and the claim is "under 400", the claim cannot be supported by that test.
Section three: extractables and residues
Extractables are the compounds that leave the wipe when it meets a solvent. They include fibre finishes, surfactants, binders and plasticisers. The test usually involves soaking the wipe in a solvent, evaporating the extract and weighing the residue, sometimes with a spectroscopic identification.
Three details matter. The solvent used (water, IPA, or both), the soak time, and the reporting unit. A residue of 0.8 mg per gram of wipe sounds small until you multiply by the mass used per square metre of surface.
| Reported value | What it usually means | What to ask |
|---|---|---|
| NVR < 1.0 mg/g | Non-volatile residue below detection | Solvent, soak time, detection limit |
| Fibre release < 10 fibres/m² | Low-shedding edge and fabric | Test method, magnification, counting rule |
| Particles < 3,000 /m² | Liquid-borne particle count | Particle size threshold, test volume |
| Ions < 0.1 µg/cm² | Extractable ionic species | Which ions, which technique (IC?) |
Units are where comparisons die
One supplier reports particles per square metre; another per wipe; a third per 100 ml of test liquid. Without conversion, the three numbers cannot be ranked. Ask for the basis and convert before comparing, even if it means an email exchange.
A simple sanity check: divide the reported count by the area tested. If the result is a number you can picture on a surface — say, under ten particles per square centimetre — the claim is plausible. If it is one particle per square metre for a cut-edge pulp cloth, ask for the raw data.
What good data looks like
It is boring. It names the method and the revision, states the sample preparation, reports the detection limit, gives the unit basis, and includes the lot number. It does not use the word "guaranteed" without a specification behind it.
It also includes the bad news: a note about edge shedding, a caveat about solvent compatibility, a statement that the data applies to a specific size. Documents that only contain favourable numbers are marketing, not evidence.
Keeping the file audit-ready
Store the report with the product reference and the lot it applies to. When the supplier changes a raw material, the report should change with it; a report dated three years before the current lot is a finding waiting to happen.
Ask for a new report annually, or on any material change. It is a small administrative habit that removes a large category of audit risk.
Do I need extractables data for an ISO 8 room?
Usually not in full. A material declaration and a particle count are often enough. Extractables become important when the surface is critical, the solvent is aggressive, or the product is a medical device.
What is a good particle count for a cleanroom wipe?
There is no universal number. Compare within the same method and the same size, and set the limit from the class and the surface, not from a competitor's datasheet.
Can a supplier test to my method?
Often yes, at a cost. If your quality system requires a specific method, ask before qualification rather than after; it is cheaper to change suppliers early than to re-validate late.
The report is not the product, but it is the only portable evidence you have. Read it the way you read a drawing: method first, numbers second, caveats last.
