eames wood problem  

call Herman miller a lot...
call Herman miller a lot of times that bent plywood does not react to change in cool air and heat, I have noticed variations on some pieces that i have seen over the years,

early versions
They are early versions of the chair. The lines have developed between the two sets of shock mounts beneath. Should I stop sitting on them? I think they haven't been used in some years

in an word yes I have ...
in an word yes I have a lounge chair that i love to look at cause it is so iconic and vintage but i rarely sit in it, I bought a new yellow lwc last month and i don't think i will be sitting in them that much
i know there are some out there that will disagree but i like to use some of these chairs like artwork and enjoy looking at them. others are just to fragile to be lounging or hanging over the sides in .

Unusual
its unusual for woodgrain to develop lines against the grain. Excessive force could be a cause, but it also could be cracks in the surface coat. Do you have any photos you could post?

In plywood
the successive plies (layers of veneer) are almost always at right angles to each other. Thus, lines which cross the grain of the surface veneer are almost always indicative of something going on with the substrate veneer.
What would cause these to appear suddenly in an old chair I cannot say, unless there has been a major change in either the way these chairs are used, or the temperature or humidity of the atmosphere they have been introduced to.

I think you're right. The...
I think you're right. The lines correspond to the underlying ply and they're in Ireland now and we're previously in Missouri.

maherj
i guess you could say a global thing

Do you think it is a warping...
Do you think it is a warping of the wood? when i run my finger along it no bump is noticeable? any suggestions to prevent it getting worse or even fix it?

Conservator
I would try calling the furniture conservator at a museum - specifically a modern museum. Someone specializing in traditional furniture may not have as much experience with something fairly modern like Plywood