Mysterious Line in Carpet

Mysterious Line in Carpet

Nature of Issue: Dark line appeared across carpet.

Carpet Type: Twist Cut Pile, Wool Mix, Beige colour


  • The clients noticed a dark line in the carpet as soon as it was fitted. They were informed by the fitter that the line would disappear after a few days.
  • After a couple of weeks the dark line was still apparent the clients arranged for a representative from the retailer to assess the carpet. He agreed the carpet did have an obvious line and referred the matter to the manufacturer.
  • The manufacturer sent their inspector to assess the carpet and although no formal report has been produced, his suggestion was that the line was caused by a fold in the carpet.
  • I was called by the retailer to carry out an independent inspection to investigate the likely cause of the line.


On first sight the dark line is not obvious and requires viewing it at various angles to see it. The line runs across the carpet in front of the sofa.


Carpet PH: 6.11 on both affected areas and un-affected areas.

  • This is normal for this type of carpet.

Physical Inspection: By running a hand over the line of the pile of the carpet you can feel a very slight indentation where the line runs.

The same test was done on the backing of the carpet, over the affected area, the backing felt consistent with no obvious signs of protruding. 

Microscopic Visual Inspection:

I compared the pile under a microscope, in the affected are and un-affected areas to find obvious differences. No obvious differences were found.

Off-Cut Carpet Inspection:

Mr & Mrs Thomas happened to have an off-cut piece of carpet left over from the fitting. On laying this out, there were slight visible lines running through the piece.

Off-site Tests:

Tuft Comparison:

Single carpet tufts were taken from the affected and unaffected areas of the carpet and placed into separate sealed bags.

  • The tufts were mounted onto card with double-sided sticky tape. The affected tufts were placed on the top row and the un-affected on the bottom row. On first inspection it looked as though there were some tufts from the affected area had a ‘hook’ shape, in comparison to the unaffected area the had a normal ‘u’ shape as one would expect.
  • The tufts were measured from tip to base. The un-affected tufts rounded to 10mm in length on both sides, the affected tufts were inconsistent in length, with only one tuft being 10mm in length on both sides. Tuft lengths ranged from 7mm to 11mm.


There is no doubt there is a line running through the carpet. The question of whether this was caused by a fold mark is very unlikely. If this were the case, I would have expected to feel a slight protruding dent on the backing of the carpet, and the line not to run perfectly straight along the tuft line. Of course, it is possible for a fold to produce a perfectly straight fold line, but very unlikely.


It would appear from the simple tests carried out above, that some of the tufts in the affected area are of slight differing lengths.

This would account from the slight indentation feel along the line and un-even length, shape and size of the tufts. This seems to be consistent along the line of the installed carpet.

I would therefore deem it likely that the uneven ‘J’ tufts to be the cause of the dark line and that would suggest a manufacturing fault.

Contact me here