Do Refractors warp?

[Jenx34]

I don't collect modern cards, but picked up a set of 2008 Topps Mantle Blue Refractors because I thought they were cool. They came in a PWE (thick DVD envelope) which looks like it got run though the machine at the USPS. The cards themselves don't appear to be damaged aside from the fact they are warped, aka not flat. The seller said that happens to refractors at times if it is too hot or too cold. My questions are:
1. Is he full of shit or does that really happen?
2. Has anyone had experience with this and corrected it? Will storing them in a rigid top loader eventually straighten them back to normal?
3. Am I screwed if I wanted to have them graded?
4. Unrelated to the warping.... Is it common to get/ship cards in these envelopes? And is it common to tape the cards to the envelope? (see pic)
Pics attached. Thanks in advance.
Chris

[bauce]

"Chromes" are sensitive to temperature fluctuations. They will 'curl'. Nice refractor design, but a huge physical weakness.

[swarmee]

As long as there are no creases or wrinkles due to the curl, I don't think grading companies take off for them (kind of like cards from vending boxes). I believe they will flatten out over time in a toploader.
And yes, I have seen some sellers tape the toploader to the package to prevent it from shifting around in the mail.

[HasselhoffsCheeseburger]

I'm a yes on both counts as well (although I didn't know the curling was due to temperature, although it makes sense).

Got a dumbbell? You could always place the card in a CS1 and place it between two books and put the dumbbell on top and see how that fares for a week.

Arthur

[bnorth]

In my experience it is caused by humidity because of the different layers of materials used.

[drcy]

Many cards, including 1950s Topps and modern Chromes, can have a bow. I don't think it will affect the grade in the grading companies' eyes.