My new arrivals!

[Onket]

Yeah, that looks like it's in decent nick!

[Stubborn Puppet]

Iron on medium heat with a low steam setting just barely enough to make it pliable. If you're nervous about putting the iron directly on the card, you can use a piece of wax paper over it... but then you have to rely completely on heat to straighten it or you have to use a fine mist sprayer to get the card/paper damp before applying the wax paper and ironing. Then, immediately stick it in between two flat, solid, heavy objects (like hardbound dictionaries or smooth metal plates on top of a desk or table) which have no paper, cloth or anything with a texture on it.

It's all about being very moderate and fast and then having the patience to let it sit under that weight for several days before you look at it.

I've done this to flatten posters, concert date cards, cardstock CD cases and the like with pretty good results. At the least, it's better than having it warped.

[payback3000]

I have ironed CD sleeves before and it's worked. A gatefold LP sleeve is a bit daunting...I will maybe have a go If I'm feeling brave this weekend. I'd hate to make it worse!

[Stubborn Puppet]

Just remember to only let the iron rest lightly on it and keep it moving. I've also used a thin white t-shirt as a medium between the iron and the cardboard.

I think I understand a little better about your trepidation though. I thought you meant that the "card" that pulls out of the cover was warped. You're talking about the cover itself. In that case, you'll want to do the same stuff, but you'll want to find something rigid and about the same thickness (or a little thicker) as vinyl itself (preferably square and exactly as big as can possibly fit) to insert in where the disc normally goes. That'll keep the edges of the cover from getting squished and creased during the ironing and especially while it's sitting between the heavy object and the table.

Be patient and confident - you can do it. Just do as little as you feel is barely effective and stop. The idea is, even if you don't get it all the way, you can always do it again. You can't undo it if you overdo it.

[payback3000]

Yep,

That's why I'm a bit nervous - its the actual gate fold outer sleeve and both halves of it...so yes i will need to pack the sleeve. I haven't tried it yet. I might get a couple of warped sleeves from a charity shop for practice.