Types of Interfacing

Hey y’all, today we’re going to talk all about interfacing, another one of those things that’s underneath in garment sewing. I’m going to be specifically talking about interfacing for clothes in this post; if you have questions about interfacing for bag sewing, there’s a great post here.

Interfacing is
a type of fabric applied to the inside of a garment to give it support, shape, and body. Think about collars, cuffs, button plackets and other parts of a garment that you might want to have more stiffness and shape than the rest of the garment. For example, the shirt below has interfacing in the collar and button placket.

When choosing interfacing, there are several properties to consider, and the choices you make are going to be influenced by what fabric you are using for the project, so choose main fabric first, then choose interfacing.

Fusible vs Sew In

The first choice is whether you want to use fusible or sew in interfacing. Choose fusible for casual, easy wear garments and sew in for special fabrics or special occasion sewing. Because fusible interfacing is literally fused to the wrong side of the fabric, it changes the behavior and drape of the fabric instead of merely supporting it as sew in interfacing does.

To apply fusible interfacing, first make sure that you’ve cut your interfacing so that the adhesive side will be against the wrong side of your fabric when finished (this is really important for pieces that aren’t symmetrical). The bumpy side with shiny dots if you look at it in the light is the side with the glue and that side should be against your fabric. Place your fabric wrong side up, then put the interfacing adhesive side down, then cover with a press cloth. Press without steam, lifting the iron straight up and down – don’t move it side to side or you could shift and wrinkle the interfacing or fabric. When the interfacing is fused, the dots of adhesive become less distinct. Trim any edges of interfacing that hang beyond the fabric.

Flip the fabric right side up and cover with the press cloth again, then steam press to finish.

Sew in interfacing can either be basted to the outer fabric within the seam allowances, or catchstitched by hand to the fabric. Catchstitching is a better option when you are working with heavier fabrics.

Non Woven vs Woven

The next choice is whether you want to use non-woven or woven interfacing. Woven interfacing will behave in the same way as woven fabric with grainlines to consider. Non-woven interfacing can be cut in any direction, so that sometimes saves fabric. My default is to go with non-woven, unless I have a specific reason for wanting woven interfacing (I might use woven if I was interfacing a drapey skirt, for example, because it would drape in the same way as the fabric, i.e. the bias would hang lower and the straight and cross grains would stand out more).

Non-stretch vs Stretch Interfacing

If you are interfacing a knit garment and you want to retain the stretch, you must use stretch interfacing. In general, stretch interfacing stretches horizontally but not vertically. Because of this, I sometimes use vertically cut strips of stretch interfacing to reinforce seams or shoulders in knit garments, as I did in this dress.

Interfacing Weight

Finally, you need to choose the weight of your interfacing. In general, pick a similar weight to your fabric. A lighter weight fabric will need less support, because presumably you chose the light weight fabric for its float and drape and you don’t want to ruin that with heavy interfacing. You can estimate how the fabrics will behave together by draping them together over your hand or arm.

Underlining vs Interfacing vs Lining

You may sometimes see the term underlining and lining and wonder how those are different from interfacing.

Underlining is to reinforce seams, inhibit stretch and help make shear fabrics more opaque to hide construction details from the outside. It is also a layer that you can tack hems, interfacings and facings to.

Interfacing is to give shape and support to the garment

Lining is to hide construction details from the inside of the garment, to give a clean finish, to allow the garment to slide on and off easily, and to protect the skin from outer fabrics that may be uncomfortable against the skin (wool coats are a good example here).

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