I've seen a lot of posts with the same complaint, is there a fix? This is an old iMac (21.5-inch, Mid 2011) I keep for some software that only runs on this old processor and OS.
Earlier Mac models
Sounds like condensation between display panel and front glass cover.
This condensation generally comes from using the iMac in damp cool place.
If you leave the iMac on for awhile, the condensation should eventually dissipate.
Some things that can help prevent condensation from forming are,
1) keep the iMac in a dry heated area of your home or office.
2) use a dehumidifier in that area of your home or office.
Sounds like condensation between display panel and front glass cover.
This condensation generally comes from using the iMac in damp cool place.
If you leave the iMac on for awhile, the condensation should eventually dissipate.
Some things that can help prevent condensation from forming are,
1) keep the iMac in a dry heated area of your home or office.
2) use a dehumidifier in that area of your home or office.
My iMac screen just developed a large gray fuzzy blob in the center of the screen.
