Monitoring for contaminants in textile product

Apparatus for monitoring for contaminants in highly elongate textile product such as yarn, comprising:

• structure defining a background for the product;
• and
• means to monitor the light reflected by the product and arising from the background;
• wherein said structure includes spaced side faces and a floor which define an elongate passageway for the textile product and thereby provide said background behind and to each side of the product;
• and wherein there is provided means to apply light diffusely to both the product and said background;
• whereby said background and said textile product may be matched so that the total amount of monitored light reflected from the textile product and arising from the background is substantially independent of the dimensions and density of the product and of the distribution of constituents in the product;
• a prescribed change in the intensity of the monitored reflected ight thereby indicating a selected contaminant or range of contaminants in the textile product.