Interfacing is a used to make fabric firmer and to help the fabric hold its shape where structure is needed. It is generally applied to the wrong side of the exterior fabric of accessories and in clothes is often used in cuffs, collars and shirt facings.
There are two types and styles of interfacing: woven/non-woven & iron-on (fusible)/sew-in.
:::: Woven Interfacing :::
This type of interfacing has visible threads and looks much like regular fabric. Like fabric woven interfacing has a grain that should be followed during cutting.
I prefer woven interfacing because it generally has a firmer hold and doesn’t tend to bubble and wrinkle as much as the non-woven type. My favorite woven interfacing is Form Flex All-Purpose. I find it works well on most quilting cottons. If Form Flex isn't available I use Pellon Stacy Shape Flex.
:::: Non-Woven Interfacing ::::
This interfacing is made from fibers pressed together and has a gauze-like appearance and usually has a stippled texture. I think this interfacing is really useful in clothing construction, but I never use it for accessories. It is very easy to melt into a useless mess of wrinkles and it separates from fabric easily. I've also never encountered a non-woven that gives much structure.
:::: Iron-On/Fusible Interfacing ::::
This type of interfacing is applied to the fabric using an iron to melt the adhesive side of the interfacing to the fabric. The adhesive side is the shiny side and it needs to be placed with the adhesive facing the wrong side (back side) of your fabric. When you purchase iron-on interfacing the fabric store will include the manufacturer instructions regarding iron temperature and how long to press to adhere it to the fabric.
When applying iron-on interfacing don’t move your iron around like you are pressing wrinkles from fabric. Simply heat up your iron to the recommended temp and place the iron face down on the wrong side (non-adhesive) of the interfacing in one spot. Leave the iron in place for the recommended time and then move it to the next section. Continue until you have adhered the interfacing to the entire fabric piece and then leave the fabric in place (as in don't move it) until it has cooled.
When using iron-on interfacing I usually cut the pieces about 1/8" smaller than the fabric piece. This gets rid of some bulk in the seams, but most importantly it keeps the edges of the interfacing from creeping past your fabric edge and adhering to your ironing board. It might not seem like a big deal but as time goes by the interfacing adhesive collects on your ironing board and ultimately transfers to your iron. This black gunk then ends up on your fabric when you are ironing and can leave black stains on your fabric, which of course isn't very fun or attractive.
:::: Sew-In Interfacing ::::
Sew-in interfacing does not have an adhesive side. It is less expensive, has fewer chemicals, and doesn’t separate from the fabric creating wrinkles and puckers and holds up to washing much better than iron-on interfacing. It is placed on the wrong side of the fabric and pinned in place rather than adhered with adhesive.
Sew-in interfacing is generally woven (though I think non-woven is available) so it has a definite fabric grain that should be followed during cutting. Launder sew-in interfacing before use.
I'm becoming a big fan of the sew-in interfacing, especially for bags and larger accessories. Sew-in interfacing doesn't offer quite the firmness of iron-on but its redeeming qualities make it a very attractive option. For bags that might be laundered more than once or twice during their useful life sew-in interfacing is the very best option.





