Greyish Smudge marks behind the glass screen.

Eighty-five pages and years of complaints! This is TOTALLY pathetic! Apple should be ashamed of treating loyal customers that have paid a premium price for their product just to have performance like this - and then to have the gall to blame it on environment. I've had this problem on all but one of my iMacs as many as three times in three years on one of them. It's inexcusable and should draw the attention of a class action lawyer.

so after 1 year of use, in the bottom left and right corner on my 27" imac i see some stains . how can i resolve this issue? i must make some heat in that area with let's say hairdryer or turn the brightness at max but for how long?

thank you

I have an iMac (21.5-inch, Mid 2011). It's a great computer and it's been kept in the same place the entire time on a desk in the spare room. Now I live in the Middle East, but I keep the temperature a constant 23 degrees Celcius. I never open the windows because there is usually a lot of dust in the air. So if you consider all the above it's been kept in a constant well maintained and working environment.

Then a blotch suddenly appeared on the right hand corner (suddenly could have occurred in the past few weeks, who knows?). Now if I've taken care of the computer properly and ensured that it's been well maintained, why should a blotch even appear? Is there only a shelf life of these computers for 3 years before they start breaking down?

Design glitch more like. I read one post of the plastic touching the screen.

It's not only iMacs. It affects Cinema displays.

The exact same issue has plagued my main Cinema Displays since they were purchased around 2009/10. They belong to my employer, and have been in their air-conditioned, clean office for their entire service lives. One has somewhat circular marks near its center. The other has some wavy marks that span about 8 inches up the side of one monitor. All marks look like grey smudges, but they must be different colors, I think, because they show up against different backgrounds. Monitor 1's circular mark disappears on a white background, but Monitor 2's marks seem visible over whites, blues, greens, reds... but it disappears on a black background.

I thought it might be burn-in, but I've set screensavers that change the whole screen's contents, often, and I've also tried letting them go dark sooner. I haven't tried burning in on purpose (that is, leaving something on the screen to let it burn in, on purpose). Should I try that?

BTW, about this forum thread: the top of this thread says it's been 'branched to a new discussion' but when I click that link, the site says it's restricted and I don't have permission. Can't imagine why; I'm just a dude who signed up for an account, same as anyone else, I would have thought.

Update: after a few days of setting my screensaver to be just white, I noticed no change, BUT... I think I discovered why it's happening to me: the screensaver never gets more than 15 or 20 seconds of play time, max.

Then the login screen comes up... and just stays there, burning the login field and icon into my screen. I tried unplugging mouse, in case it was the building's vibration.

That means I can't actually apply the fix detailed in Apple's link, not unless I can make my machine show the screensaver instead of the login screen.

Of course I can set the screens to turn off, but then the suggested anti-burn-in fix would be impossible. It only works if the monitors are on and showing all white, right? Think so.

UPDATE: for the monitor that keeps burning in the login window, the white-screen fix works. On Mondays, that burn-in is gone.

The same fix does not affect the other monitor. It's stains look a lot like the ones ikkei posted. They haven't gone away after more than a month of using a white screensaver and also opening a plain white TextEdit window on that section of that monitor for hours at a time.

Yours is quite impressive! My 2009 iMac has had a set of discolorations for years that fade after the display warms up. But now I have a streak that is more persistent and doesn't fade.

I am sure Apple will never fix this, but I'm interested to know if there are any 3rd party solutions.

If you are seeing discolorations that fade after the display warms up then it sounds like condensation may be forming on the inside surface of the glass panel on the front of the iMac. By any chance do you live in an area with relatively high humidity? Does the issue typically occur after you start up the iMac when it's cold? In a high humidity environment the moisture in the air can condense out and form droplets when it comes in contact with a cooler surface like the iMac.

Today it was my turn to discover the existence of this epic thread.

I have a 27'' Late 2012 iMac bought in June 2013 in Bulgaria. The smudges appeared today. One is in the lower left corner, the other in the lower right corner. They are relatively small, but as I understand they're likely to grow. I'll talk to Apple but judging by some of the comments I've read throughout this thread, I'm not keeping my hopes up.

It's amazing that this thread was started in January 2010 and the underlying problem hasn't been addressed yet.

I've noticed similar patterns on my screen too (a mid-2010, 21.5 inch i-Mac). I can see it both when the screen is solid white or solid green like you show. I suspect much of this is a static dust pattern as is often seen on plastic parts that have been in storage for a time. I tried capturing a portion of the screen to see if it was in the image the machine projected. It is not, therefore not software related. If it is indeed a static dust pattern, depending on what the dust consists of, it could easily get worse (more prominent visually) in high humidity conditions. If it is composed of something that has a low tendency to absorb water, it probably wouldn't change much in high humidity conditions. I've suspected that this dust is on the inner surface of the glass of the display. I suppose it is possible that it could be on other parts of the monitor display (the LEDs themselves, etc). On my machine the glass should be fairly easy to remove and clean as it is held on with magnets. I just never felt it was objectionable enough to go to the effort required to try it.

Interesting thought on the role of condensation. We're in Minnesota, which can be moist in summer -- though we air condition this part of the house. There's a laser printer nearby -- supposedly toner dust tends to accumulate in these displays (? electrostatic effect?).

Is an aggravating design defect. I wonder if Apple ever fixed the problem. I'm leary of iMacs after this, tend towards buying a portable with external monitor.

I have a 27" Cinema Thunderbolt and it has a smudge in the lower left portion of the screen. Yes, the monitor gets pretty hot after being on even an hour or two. It's a disgusting development and a smear on the reputation of Apple (no pun intended).

Yes...greenish/grey smudges along the top of my 2009 21.5 inch IMac, on the left and near the right side too. And, yes, I live in a hot, humid place ( Rio de Janeiro). So the problem would seem to be definitely related to these climatic situations. I agree entirely with you...At the price they charge for an IMac, Apple should build and test their products to withstand conditions across the world, not just in California.

This looks worse than mine but I know how you feel. I'm getting yet another screen replacement on Monday, one of many and I don't think it's over yet, it's a designer flaw without a doubt.