I don't know of any way to flatten them without some sort of damage. They curl because the plastic shrinks and the paper it's bonded to doesn't. As the plastic dries and shrinks it also gets a bit brittle, so flexing it can cause cracks and/or coming loose from the paper.
If the plastic is still pliable it might work to put them in screwdown holders. But that will flatten the ridges.
Of the 3-d stuff I have, the Kelloggs have done ok if kept out of light The sets in the original mailer have curled the least, ones I bought at flea markets have done the worst. A 3-d basketball set I have in screwdowns is doing just fine.
I have some non-card 3-d stuff. Some large 3d pictures by the inventor of the process are doing really well, no problems at all and only a hint of curl- maybe 1/4 inch over 14 inches. Some 3-d Postcards are doing very poorly, when I got them they were curled nearly back over themselves along the edge. They probably got lots of light exposure.
Steve B
|