Understanding Underlining and Interlining

Underlining, how I love you, let me count the ways... infinity, just infinity. You make my efforts worth it every time. It is often referred to as a couture technique, and in all honesty, study couture is how I discovered it. But since being taught about how to utilize this, it is my preferred way to optimize my sewing efforts. It is my secret step to make my sewing easier and raise the quality to my garment. It can provide a secret and sturdy base to attach closures, stabilizers and other internal details, like boning channels and waist stays. You can place all your markings on the underlining, so you don't have to worry about your marks bleeding through to the right side of the fashion fabrics. For those of you who have yet to be introduced to underlining, let me lay out the concept for you.

What is underlining? Why can't I just add a lining?
Good question. Lining and I are also good friends, but it serves a very different purpose than an underlining. Lining is basically adding a version of the fashion fabric in a lighter fabric to hide the internal construction details. It can hide a mess of things and it can improve the tactile feeling of the garment. It happens near the end of the construction process.

Underlining is joining each piece of your fashion fabric with a replica of the same pattern pieces in a "backing"fabric before construction begins. The two fabrics will then act as one, adding strength and stability. It reduces wrinkles and can reduce transparency in lighter colored fabrics. If used in pants and blouses, it can hide panty and bra lines. It also has the added couture benefit of hiding any hand stitches from peaking through.

To add a little more confusion to the whole inside of the garment, there is also something called interlining. Some will use this interchangeable with underlining, but that is not entirely accurate. Interlining is an underlining with the added purpose of adding warmth without adding bulk. If it added bulk it would be insulation. This is typically applied to jackets and coats. Interlinings can be attached to either the shell or lining because it is truly all about the warmth.

Now, back to our main event.

But how do I use this to elevate my sewing game?
My goodness, you ask great questions! Start by cutting out the pattern in your underlining fabric and transfer all the necessary markings to the underlining. I do it this way first, so that I can lay the underlining over the fashion fabric. If I am using a slightly sheer underlining, I can use this to help with "placement" if working with a print or an embellished fabric. Than join wrong sides of the fashion fabric to the underlining, so that the markings are visible.
Attaching this underling to the fashion fabric is typically done by hand in the couture universe, but I have over locked the two together with similar results. If you go this route, you should be warned that it is easier to get these off of being 1 to 1. They must be 1 to 1, or you will have a hot, saggy mess on your hands. You loose full control when done by machine.

Once connected, each double piece is treated as one for the rest of the construction process.  It is really that simple.

What do I use to underline?
The trickiest part of the process can be finding and sourcing the best underlining for fashion fabric. There are no hard and fast rules when it comes to fabric combinations. In fact, you could even use different underlining, or interlining, in different parts of the garment if needed. For example, in a jacket, you might want added warmth of a flannelette in the front and back of body, but it could be too much in the sleeves. In this case, you could use a cotton batiste or lightweight broadcloth in the sleeves. If you are working with a stretch woven, you would want to choose a fabric like a swim lining or a tricot, so as to not loose the stretch properties. Don't be afraid of underling knits either. Just be sure you apply the same rules as a stretch woven. Choosing an underline does take a little critical thinking, but it is really worth it.
You can even use an underlining to alter the color of a fashion fabric. For example, if you have a white satin, or a slightly sheer fabric, that is just a little too warm for your tones, a cool color can be added to slightly alter the color tones. This is just going to be able to be slightly change the tone. It will not color correct a color that is way far off from working for you.

But doesn't this change the fabric hand and drape?
Yes. Simply, yes. You can be minimize it by choosing a fabric with similar properties to the fashion fabric. Be sure you choose a fabric that lighter in weight and as soft or softer than the fashion fabric. You can also go the other way and maximize the change. If you want the fabric to be stiffer and have a little more body, you could try adding a silk organza. If you are just interested in adding strength, use a muslin or cotton flannel. Or you can add a touch of drape with a silk crepe de chine.  You could also add thickness by doubling the fabric itself. One rule you want to always abide by is chose a tightly woven fabric to prevent any stretching and to preserve the structure and shape of the garment.

There is one fabric I don't typically underline. Rayon can have a tenancy to "sag" over time and becomes more pronounced with wash and wear. So, in short, underlining is awesome, but it is not always the answer to great construction.

Happy Underlining!