Interfacings and interlinings can be a contentious part of bag making, not least because of the bewildering array that can meet you in the average fabric shop. Understanding the purpose of each one, however, may help you the next time you face this conundrum! I usually use Vlieseline (formerly Vilene) interfacings and interlinings as it’s the most readily available to me in the UK, but when referencing specific items I’ve tried to include equivalents by other popular brands.  I apologise for the fact that there aren’t many photos in this post, but interfacing/interlinings are really quite hard to photograph and get your point across, so I had to make do with the rolls I had to hand, sorry about that!

Interfacings Versus Interlinings:

Firstly we should differentiate between interfacings and interlings:

• Interfacings are there to provide stability to the fabric
• Interlinings are there to provide structure to the finished product

It is possible to make bags without interfacings, but still have interlinings – usually bags made from heavier weight fabrics, or you can have bags with interfacings, but no interlining – for example a simple zippy purse. You can also make simple bags without either, such as a tote bag from home decor weight fabrics, or from a heavy leather that has its own stability and structure inherently. Depending on the size and complexity of the bag you can also choose to apply interfacing to the lining fabrics as well – I would do this with big bags, but not so much on a little clutch.

Both interfacings and interlinings are often made in black as well as white, with the black designed for use with dark fabrics and the white for lighter fabrics, but shops seem to tend towards stocking the white more. It depends on the weave of the fabric you’re using them with whether or not it will make a difference – if it’s a tightly woven, opaque fabric then it probably won’t make any odds if you use the standard white, but if it’s a slightly looser weave, live a linen, then you might want to hunt down the black version for dark fabrics.

Interfacings:

Interfacings come in 2 varieties, fusible and sew-in. As the name suggests, fusible is stuck to the fabric by melting the glue embedded on one side via the heat from an iron, while sew in is generally basted to the fabric in the seam allowances, but is otherwise loose from the fabric. In general, unless you are using a fabric that you can’t use with an iron, the fusible option is the most commonly used by pattern designers.

Fusible Interfacings:

Fusible interfacings split into two types, woven and non woven, which break down as follows:

Non Woven Interfacing:

This is the stuff that feels papery when you touch it. Made from synthetic material, it is designed to stabilise fabric used in clothing specifically. It comes in a variety of weights which are meant for things such as waistbands, collars, cuffs etc where the fabric is expected to come under strain or where it needs to stand up a bit. It is really not suitable for bag making, and it’s the kind I most often see people complain about not looking right because it can leave fabric with quite a peculiar texture, especially if the glue hasn’t been set correctly. As someone who had no idea when they started out what type to use (big brand patterns never being that specific), I can tell you that the bags I made with non woven interfacing are the ones that look distinctly odd now, especially where creases and things have formed (they probably looked odd when I made them too, to be fair, I just didn’t know any better) Where the woven variety flows with the fabric, the non woven deliberately doesn’t because it’s not designed to do that.

Woven Interfacing:

This is a woven fabric with adhesive on one side – it comes in several weights, but the most commonly found ones are around the same weight as a quilting cotton. When applied to the back of a fabric it is designed to give it more support than the fabric alone would have, but also to drape with the fabric. In bag making it is usually applied to lighter weight fabrics, such as quilting cotton, before interlinings are used. The most commonly found woven interfacings found on the market are Vlieseline G700 and Pellon Shapeflex SF101 (which are pretty much identical, so if you are in a country that tends more towards one of these, don’t worry about it if you have a pattern requiring the other).  Note that on the end caps there are usually markings showing washing/ironing instructions, so it’s worth checking them out in the shop when you pick them up.

Sew In Interfacings:

These break down in a similar way to the fusible versions above, and in fact if you can’t find a non-fusible version you can totally use the fusible version without actually gluing it in place (just remember that the glue is there if you wave an iron at it later ;o) )

Interlinings:

Like interfacings, interlinings come in both fusible and sew in versions, but in a rather larger variety. For the most part they are made from synthetic materials:

Fusible Interlinings:

Fusible Fleece:

This is an entirely synthetic product which gives a slightly spongy feel to the fabric it’s applied to. Coming in 3 different weights, they provides a fairly low level of structural support on a larger bag, but in terms of smaller items such as zippy pouches or bags where you don’t want a rigid structure they can work very well. Vlieseline makes 3 versions (which they seem to have recently rebranded as fusible battings): H640 is the highest loft option, which I’ve used in simple small-medium sized handbags, then there’s H630 which is about half the thickness of H640 and works at clutch size, and finally 272 Thermolam, which is a compressed fleece, and which I tend to use in zippy pouches. Pellon make a slightly different set of options, TP971F is nearest to Vlieseline’s H640, but the H640 is a bit thicker, 987F is closest to Vlieseline’s H630, but the 987F is a bit thicker, while TP970 Thermolam plus is similar to Vlieseline’s 272. To be honest it’s not going to be the end of the world if you have to use one brand over the other, as a mm or two in thickness here or these isn’t going to make that much difference. As a tip, when using any kind of fleece you should trim your seam allowances to prevent bulk in that area which can both cause the seam to gape a wee bit between stitches, and for the seam allowance itself to stick out awkwardly – for fusibles I tend to do this at the cutting stage, but for sew-in versions you can trim after sewing.

Fusible Foam:

Foam interlinings are relatively new on the market, really only gaining popularity within the last 4-5 years. Some brands have gone with both fusible and sew in versions, while others have stuck to just a sew in version, as you will see below. Foam allows for much greater structure in bag making than fusible fleece since it is much denser and therefore stands up better, even when fused to heavier weight fabrics. Both single and double sided fusible options are available – the double sided tends to be a bit thinner, as it’s really designed for simple bags where the outer will be fused to one side and the lining to the other, generally with the idea of quilting being used on the piece once fused. Single sided fusibles allow for separation of exterior and lining for more complex bags, and work well to create bags which hold their shape. As with fusible fleece, trim your seam allowances. My favourites of the fusible brands are the single sided fusible Bosal In-R-Form and Pellon Flex Foam. Both Bosal and Pellon also do double sided fusible versions.

Firm Fusible Interlinings:

The only other interlinings that I tend to use are the ones designed for making pelmets, which can be either a sort of plasticky finish or a sort of thick cardboard type finish. These can be useful for the bases of bags if you’re trying to make them particularly stiff, and I have occasionally used them in the sides of small clutches that I wanted to be rigid. With these interlinings you especially need to trim your seam allowances, otherwise it can do some very peculiar things to your seams, and in this case I always trim before sewing. Sometimes I use the fusible versions for these firm interlinings, but I have also been known to get the non-fusible version and hold it in place with a piece of woven fusible cut to the full size of the piece, thereby keeping the interlining out of the seam allowance, but also preventing what can be some quite nasty bubbling/crinkling with the fusible versions if you haven’t followed the fusing instructions to the letter. Versions of the fusible interlinings include Vlieseline Decovil, Pellon 520 Decofuse, 809 Decor Bond or Peltex 71F (single sided) or 72F (double sided)

Sew In Interlinings:

Sew In Fleece:

This works in the same way as the fusible version, and would be my choice if using fabrics which could not be used with an iron. Versions include: Vlieseline 280/281 equivalent to the fusible H630 and 295, equivalent to the fusible H640; Pellon 9 oz and 12 oz Legacy, equivalent to the Vlieseline 280 and 295 respectively, as well as the TP970 which is the non fusible version of the Thermolam.

Sew In Foam:

One of the biggest players in the foam market is the By Annie’s Soft & Stable which launched at Quilt Market in 2014 and is popular because it can be used to quilt the outer to the foam without the risk of a fusible version maybe gumming up the needle (I haven’t had this issue with the fusible, but then I tend not to quilt it, just add pieces such as handles etc) The advantage of foam for quilted bag parts as opposed to regular batting is that it has far more body than traditional quilt batting. Other players in the sew-in market are Bosal In R Form sew in, and the Vlieseline Styl-Vil while some people have had success with car headliner, which is the fabric backed foam that you find covering the ceiling of your car. Headliner does come in varying thicknesses though, so it might be worth ordering samples to check before going down this route.

Quilt Batting:

For those wanting a little body, but not as much as fleece or foam would give, there is always quilt batting, and in fact this is often used in conjunction with canvas or duck cloth on the back to create quilt as you go panels for bags.

Sew In Firm Interlinings:

The sew in a fusible versions of firm interlining work in pretty much the same way. As I mentioned in the fusible section, if I’m using sew-in versions of firm interlining I tend to cut it out without the seam allowance and then hold it in place with a fusible woven piece that includes seam allowances. If you couldn’t use fusible at all on your fabrics, then you could also hold it in place with a sew-in woven interfacing that was basted in the seam allowances. There is a slight risk that the interlining could move about a bit while sewing the seams together (since basting is usually done outside the seam line) so it’s worth keeping a close eye on it at that step. Sew-in versions of firm interlinings include Vlieseline S133 and S520, Pellon 65 and 926 or C&T’s Timtex.