Working with fusible interfacing

Many patterns will require interfacing to reinforce a particular panel or structure in the pattern--think of it as hairspray for fabric. Collars and lapels are popular candidates for interfacing for the new seamster.  For our purposes early on, we will always be working with fusible interfacing, which is applied to the fabric with an iron. Interfacing comes in a variety of weights, most of my early projects have focused on using lightweight interfacing.

It's not a bad idea to just have a few yards of lightweight fusible interfacing on hand for your sewing projects, rather than buying it on a per-project basis, but of course, your patterns will tell you how much you need so it's hardly a requirement, and sometimes the amount of interfacing your need and the pieces are so small that you can use scraps from a previous project. You don't need to worry about finding "the grain" of the fabric with interfacing.

Fusible interfacing is a woven material on one side, and then a heat-activated glue on the other. because of this you do not want to pre-wash your interfacing when you pre-wash your other fabric. You will also want to avoid ironing your interfacing until you are ready to apply it.

You will be able to determine the glue-side fairly easily simply by touch. The fabric side of the interfacing will be smooth, whereas the glue side will be a little bumpy. If you examine it carefully, you will be able to see the little beads of glue as well. 

Always iron on the fabric side of the interfacing, do not iron the glue directly or you will have a mess to clean up!

Typically, interfacing is cut out using an existing pattern piece, so that it will have a "mate" with the cut-out fabric. You will want to follow the instructions on the pattern's cutting layout for the interfacing.  Sometimes, you will need to review interfacing instructions as interfacing will only use a portion of a fabric piece, but this will be indicated on the pattern and the cutting layout.

Interfacing is an invisible feature of the garment. Sometimes it is fully-enclosed by fabric (for example, most lapels) and sometimes it is folded under the interior of a a garment (for example, a front collar). In either event, unless the pattern specifies otherwise (and I have never seen one do so), you will match the interfacing to the fabric, laying the glue-side of the interfacing against the wrong side of the fabric. Make sure you match notches and dots just like you would when piecing together any other part of your pattern.

If the interfacing is going to be fully-enclosed, the pattern will usually tell you to clip the corners of the interfacing to better turn out the corners when it comes time to turn your collar or lapel (etc) inside-out.

Once the interfacing is in place, take a nice hot iron and lay it on the woven side of the interfacing, pressing down firmly to help form a bond. Let it sit for a couple of seconds to melt the glue to the fabric (bearing in mind not to burn the fabric if you have a more delicate fabric), and then lift the iron and place it on another part of the piece. Continue doing this until you have covered the entire piece. Do not push the iron around or you might accidentally nudge the interfacing off of its fabric mate before the glue has set. Once you have secured the interfacing with the glue, you can iron normally.

Now that you're done, you should have one "right side" of the fabric, and then one "facing side" which is the woven side of the interfacing. This piece is now called the facing piece.