Rubbing (Crocking) Fastness: Dry and Wet Results Explained
Crocking failures show up as colour transfer onto upholstery, bag straps and shoes, and wet results are usually the first to fail.
The practical guidance below is written for buyers and product developers who need a specification that a mill can meet.
Test method
A standard white cloth rubs the specimen under controlled pressure in a crockmeter, and the staining is graded.
Buyers who set expectations at the development stage spend far less time resolving complaints after the season has started.
Dry versus wet testing
Wet testing uses a specified wet pick-up and is more severe, which is why it is the limiting result for many dyes.
Fix the limits for the whole size range, not only for the middle size, as grading changes the numbers involved.
- Confirm the numeric range and the test method in the specification
- Keep an approved physical standard at the machine
- Retest after the agreed care regime before shipping
Typical causes of failure
Surface dye, insufficient fixation, pigment print binder problems and stiff finishes all raise rub-off.
Train operators on what the parameter looks like when it is wrong, since most defects are visible long before testing.
Fibre and shade influence
Deep shades, indigo-type dyes and dark prints are the usual problem areas and need tighter targets.
Repeat the test when the fabric, the mill or the finishing route changes, as previous results no longer apply.
- Request test reports on production fabric, not on development samples
- Verify the sampling plan and the number of specimens
- Store reports with roll or lot identification for traceability
Acceptance levels
Grade 4 dry and grade 3 to 4 wet are typical minimums, with higher requirements for skin-contact products.
Ask for the cost of the requirement to be shown separately, so it can be weighed against the benefit it delivers.
Summary
Used as a checklist in development and again before shipment, the points above prevent the most common and most expensive failures.
