How do I do this without starting over?

[nachturnal]

So I've had this idea of a pleated bag for a really long time, and when I got a sewing machine for my birthday, I pretty much got cracking on it.  Problem is, I've already started assembling one of the panels for the exterior of the bag — but I've forgotten to wash the fabric or add any interfacing.  I plan to use this as a bookbag for uni.  One fabric is quilt-weight, and one is a heavy homespun cotton.  Does it matter that I've forgotten a couple of things, or will the bag hold without it?

[little me]

If it's the kind of heavy cotton like the home dec cotton, then those usually aren't washable - it's dry clean only. Depending on how many books you plan to carry, your bag may sag a little.

[nachturnal]

If it's the kind of heavy cotton like the home dec cotton, then those usually aren't washable - it's dry clean only. Depending on how many books you plan to carry, your bag may sag a little.

Will interfacing stop my bag from sagging?

[little me]

If you're talking about the bottom - what would be great would be to get some kind of light plastic you can cover in the same fabric to use as a "floor", that will help a lot. Interfacing alone will not help w/a lot of books.

People use plastic canvas (used for needlepointing), but I think it's too flimsy. There is a plastic they use for quilting for cutting out shapes that works great if you can find it. Otherwise, cutting a flat plastic container & sanding the edges would work great - cut it about 1/4-1/8" smaller than your bottom. Also what I did once was, I made the edges about 1" bigger on all sides - the plastic was framed. This gave the "floor" a skirt that came up the sides & prevented small things from falling underneath that you have to dig for.

[nachturnal]

If you're talking about the bottom - what would be great would be to get some kind of light plastic you can cover in the same fabric to use as a "floor", that will help a lot. Interfacing alone will not help w/a lot of books.

People use plastic canvas (used for needlepointing), but I think it's too flimsy. There is a plastic they use for quilting for cutting out shapes that works great if you can find it. Otherwise, cutting a flat plastic container & sanding the edges would work great - cut it about 1/4-1/8" smaller than your bottom. Also what I did once was, I made the edges about 1" bigger on all sides - the plastic was framed. This gave the "floor" a skirt that came up the sides & prevented small things from falling underneath that you have to dig for.

I was talking of the sides, whether I'd need to reinforce them.  I was just going to have a basic bag shape, though now I think of it, I may make it like more of a rectangular prism to make it with a bottom.

Thanks!

[CraftyChef]

Washing the fabric ahead of time isn't really a biggie for me. Washing machine is OK as long as you don't put the bag in the dryer. Air dry, then iron when still a little damp. I do that for all my bags and they come out just fine. Just about all my fabrics are interior design quality.

(Er, that's COLD water, GENTLE cycle only)

[nachturnal]

Washing the fabric ahead of time isn't really a biggie for me. Washing machine is OK as long as you don't put the bag in the dryer. Air dry, then iron when still a little damp. I do that for all my bags and they come out just fine. Just about all my fabrics are interior design quality.

I generally don't wash my bags anyway (I had a bad experience with a bag losing most of its colour after being washed and AIR-DRIED, for chrissake), but I'm fairly paranoid.

I don't think any of this will shrink, it's fairly heavy-weight cotton.  Even so, better safe than sorry?