Let's Talk Interfacing
There are many different names and brands of interfacing, each type affects your fabric differently to produce different results
In order to help you get to grips with the subject of interfacing for bag making, I would like to start off by sharing with you the interfacing I use in all my bags and that is woven interfacing.
Woven interfacing has a soft drape, very similar to the drape of your fabric, and by fusing it to the wrong side of your fabric with an iron , it makes it ever so slightly stiffer, a bit like if you were to starch your fabric.
Woven interfacing acts as an enforcement to make your fabric more durable, stronger and easier to sew with, your machine feed dogs don't chew it up but the main reason I use it is to reduce wrinkles when using foam (check out by separate blog post on foam).
Also, when fusing FOAM interfacing to your fabric, woven interfacing somehow reduces the number of wrinkles you have in your fabric, particularly the exterior of your bag which form when you turn your bag right side out after attaching your lining, this is often referred to as birthing your bag in the bag making world