Quality Control

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Criteria
During development all CFT testmaterials are subject to two types of tests; A detergent comparison test, to detect the Discriminative Power of the product, and a dosage/response test, to test the reproducibility. Obviously we aim to create a testmaterial with a high Discriminative Power and high reproducibility.
During production and processing we also check the within-batch variability. Our standard rule to accept 2% point variation within one side of the fabric. Due to several reasons it can be that the two sides vary more than 2% point from each other, the darkest side is then always marked as front. For very dark testmaterials we only accept 1% point of variation. All the material outside these boundaries will be disgarded.

Batch to Batch Control
C.F.T. soiled testmaterials are always subjected to a strict quality control before delivery. The main criterion here is the response to certain treatments within a wide range of concentrations. The most recent results of these Quality Control tests are published on our website. You can download the QC-sheets with the following link: Download a QC-Sheet Below you can see an example of such a Quality Control Chart. Except for the response, it gives the Ru = unsoiled reflectance, and Rs = soiled reflectance values.

qc1
The necessary tests are being performed by means of a 7 kg Wascator FOMLAB machine, in which the main wash is carried out in 1 litre polyethylene bottles, each filled with 500 ml of stock solution in an increasing concentration. At the end of the main wash, the bottles are pored empty into the machine and subsequently a normal cold rinse cycle is being carried out. After the rinse cycle, the washed pieces of test fabric are dried, in most cases ironed, and next the reflectance is measured at 460nm.
The Rs values are kept as constant as possible. Nevertheless, variations may occur due to batch-to-batch variations in the natural raw materials.

Measuring of soiled testmaterials
Testmaterials are best judged by reflectometry as mentioned above or by chemical analysis. An objective assessment, using a spectrophotometer, yields two sets of data:

 

  • The initial, soiled reflectance: R-soiled (Rs)
  • The reflectance of the washed cloths: R-washed (Rw)

From these values, the difference in reflectance – ∆ (delta) R can be calculated (∆R=Rw-Rs) and used as a measure of soil removal. Sometimes the unsoiled reflectance Ru is used to calculate the absolute soil removal.