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I'm early in the process of making a leather doctor's bag (also known as a Gladstone bag), in this kind of shape:

Foster & Sons Gladstone bag

I've bought a side of ~2mm cowhide for the body, but I know from past experience that it's too flexible to stay in shape while standing on the floor without something to stiffen it.

So, what materials can I use to stiffen the leather in the straight part of the bag's sides?

I've considered the following:

  • Card (as used here) - this worries me because it will degrade very quickly when wet.
  • Paperboard (chipboard in the US, as used here) - similar issues to card
  • Interfacing - I've never seen this used for leather goods but it's a plausible material
  • Sheet plastic - this is lightweight and waterproof
  • Sheet metal (probably aluminium) - strong, but probably not flexible enough and heavy
  • Steel framing (rather than a full sheet) - this seems to be what hard briefcases use for strength but is almost certainly too stiff.

I'm looking for something that will enable the bag to stand upright without sagging, but I'm making a bag not a box, so it needs to retain some flexibility.

  • Partial 'answer' so as comment: Be careful with plastic, it comes in many different kinds. Some will age fast and break just when you need them. Others will just be too floppy to work, or even too stiff. And almost all will allow wetness to stay on the inside of the leather, promoting problems in the leather if not handled right. – Willeke Nov 17 '17 at 18:16
  • @Willeke I hadn't thought of this. Is degradation much of an issue if not exposed to sunlight? – walrus Nov 20 '17 at 9:48
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    it really depends on the kind of plastic. It is not only sunlight that can be an issue, it can also be bending. There are very many kinds of plastic, so you can find kinds that would work, but you will need to be careful selecting. – Willeke Nov 20 '17 at 17:01
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One thing not on your list is steel wire.

This is a sort of steel framing I suppose. But it can do a lot while remaining light and flexible. I would think you want something in spring temper, so perhaps piano wire of sufficient gauge. I suppose whenever I've seen these it's been mild steel though, somewhere around .050-.100" diameter.

"U"-shaped members on each side and each end might do the trick. They could be sewn into seams or otherwise concealed.

Interestingly, these members resist torsion (twisting) as well as bending. So, for example, if you wanted a bag that didn't flop down but was free to pull apart for access at the top (and pull together at the top to close), you could place a square wire frame at the bottom and a U or square frame on the sides only (not the ends). The frame would tend to make each side "hinge" in and out as one, roughly like the cover of a book, rather than having to pull each end separately to open.

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Use E V A foam sheets (3mm to 8mm thickness) The EVA has many different uses but for leather crafters it is used for stiffening of bags like laptop bags and also serves for protection. The sheet size is 1m x 2m. EVA foam is a closed cell foam that provide durability and strength.

  • Welcome to Arts & Crafts. This is a good suggestion. If the foam is bonded to the leather, it will provide more stiffness than if it's just another layer. – fixer1234 Mar 14 at 15:53

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