[riskable]

I came here to say this... Those FRAKTA bags (http://www.ikea.com/us/en/catalog/products/17228340/) are 100% polypropylene (thin strands, even). Polypropylene breaks down under ultraviolet light. The fact that the weave of the cloth is made from fine strands of polypropylene means that it will break down very quickly in the sun.

There's a "fix" though that should be good enough for a camping trip or two! Coat the bag with a powerful sunscreen. I'm not talking about those "SPF 50" spray bottles--those will wear off pretty fast. No, use Butt Paste:

http://www.buttpaste.com/

Yes, it's diaper rash cream but it's 16% zinc oxide which is the primary ingredient in many sunscreen lotions/sprays. Even better, because it's a thick cream it will actually stick to that slippery blue Ikea polypropylene fabric and do a decent job at protecting it from the sun.

[dpark]

Making a cheap bag into a greasy, sticky cheap bag doesn't seem like a net gain.

[riskable]

Yes, butt covering with Butt Paste would be an excellent metaphor of its quality!

...which is precisely why I made my "protective" suggestion in the first place =)

[slackstation]

Cheap? You can buy one from this guy for only $230 (!)

[chronolitus]

I found that very high at first, but then realized it's probably a pretty fair valuation of his time.

In the sense that you'd be silly to pay that price for that bag, but he'd be silly to sell it to you for any less if it takes him 10 hours to make it.

[Freak_NL]

I am positively surprised to learn that a product called 'Butt Paste' exists.

Still seems that economically speaking it might be cheaper to create such a backpack from a more suitable cloth instead.

[randlet]

How about Anti-Monkey-Butt-Powder? [1] Popular in motorcycling communities.

[1] http://www.antimonkeybutt.com/

[Poiesis]

It exists, and it is wonderful. Hands down the best stuff for diaper rash I've ever used.

[hatsunearu]

Only in DIY lala land do people apply sunscreen to their "hacked" backpacks...

[vvvv]

Do you use Butt Paste as a normal sunscreen for yourself?

[jlb1982]

I've found it great for surfing. Granted, it makes me look like a mime, but the paste stays on in the water and blocks the sun.

[otoburb]

No, unless you deliberately want to look like you just finished tussling with a toddler armed with a white paint brush.