Napped fabric has a raised layer, often referred to as a pile, that is made during the weaving process. These fabrics have gone through a finishing process where the fiber ends are raised to the surface, and then are either clipped, brushed or left upright.
The nap goes along the fabric lengthwise. Sometimes the nap can be felt by running your hand over the fabric. If you’re going in the nap direction it will feel smooth, and against the nap the fabric will stand up more and feel rough.
Also, each angle of the nap reflects light differently. For example, if you hold the fabric with the nap facing down you might see a lighter or darker shade than if the nap faces up. That is why it is important to always follow the “With Nap” layout as provided by the pattern when sewing with napped fabrics. That way, once completed, all material will face the same direction when worn. Otherwise you could end up with a multi-colored garment.
Some fabric naps are more noticeable than others; some are highly noticeable, while others are hard to tell whether or not they have a nap.
If you are not sure if the fabric has a nap, hold it up in different directions and if you see different shades then follow the with nap layout.
Another way to check this is to lay the fabric side by side, with the nap going up on one side and coming down on the other. If you see a difference in the shade then use the nap layout. And if you’re not sure, you might want to use the nap layout anyway just in case.
One thing to remember is that when you are using the with nap layout you will need more material. So it’s best to check for this at the fabric store before you make your purchase. The pattern envelope will have the information on how much material you will need. Make sure to buy enough the first time because it may not be there when you come back the next time, or it might be a different shade. It is always better to have more than enough then not enough.
Velvet, velveteen, velour, flannel, corduroy, terry cloth, chenille, mohair, and cashmere are some examples of napped fabrics.
Some fabrics like satin and moire taffeta, do not have a nap, but the effect will be the same and must be cut out using the with nap layout. Print fabrics without a nap should also be cut using the with nap layout so that the prints will all face in the same direction.