Frequently Asked Questions

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Nov 19, 2015

IEC/AHAM Stain Strip: Dimensions

Why do strips from Swissatest and wfk have slightly different dimensions?

The specification for the IEC and AHAM stain strips is that the swatches shall be 12 cm x 12 cm. We have cutting dies that give us swatches of exactly that size. When the swatches are sewn to each other the sewing machine that overlocks the edges has to cut off any piece of the swatch that exceeds the seam - we process that as accurately as possible and with that minimize the 'loss' of fabric to something like a mm or max. two. As the swatches are overlocked on all 4 edges that can lead to a final swatch size of approx. 11,7 cm x 11,7 cm. This size can be measured by determining the 'width' of the strip.

Regarding the length one has to consider that some of the fabric is in the seams connecting the swatches (approx. 5 mm), therefore the resulting 'length' of each swatch (i.e. the visible swatch area in the direction of the strip length) is 11,7 cm - 1,0 cm = 10,7 cm. The total length of the strip can therefore be estimated to be around 5 x 10,7 cm + 2 x 0,5 cm (for the outer edges left and right) = 65,2 cm.

Summary: The free and visible area per swatch that is available for measurement in the test is in fact approx. 10,7 cm x 10,7 cm, the outer 5 mm on each side is hidden in the seams, and the way the swatches are sewn to each other the seams between the swatches do not add to the length of the strips.

We are aware of the fact that Swissatest cuts the swatches to be 1 cm wider in the length (i.e. 12 cm x 13 cm) so that the over all length of their strips is more than ours. We have never considered that as standard compliant or the intent of the standard requirement. However, the slightly diferent swatch size is not critical or relevant for the technical aspect of the test.