Home > Mac > iMac 27″ screen displays dark stains, spots and patches

iMac 27″ screen displays dark stains, spots and patches

My iMac 27″ which has performed flawlessly since I acquired it in March of 2009, has started to develop dark patches here and there, across its once pristine façade. And this pisses me off, mightily.

It all started in summer of 2008 when my first iMac (the new Intel Aluminium 24″ iMac) started to develop dark stains on the screen…

Mac 24″ roasting with dark patches on screen (12th August, 2008)

There were various theories bandied about, such as overheating, condensation leading to mould, dust sucked into the system, etc… But my  room is airconditioned and on the 9th floor of an apartment, above the majority of dust and grime. And although the room sometimes reached 35 degrees (right on the edge of operating spec) or so, there was never any condensation and I always used air conditioning when I with operating the computer.

Before discussing, let me fill you in on a little background with this post:

Aluminium iMac 24″ screen displays patches, uneven brightness and dark spots saga recap

So you can see that I have a history of nasty screenage.

The effects are not so great that the screen is unusable, but in my experience these things never improve with age.

So, here we go again, it is with a sense of deja vu and disdain that I contact Apple this afternoon to see what can be done.

Here’s the money shot:


picture of imac 27 LED backlit screen showing mottling

This iMac 27" LED backlit screen has recently developed a mottled appearance


  1. Bluecat
    December 30, 2010 at 11:05 pm


    I have the same problem. Not as much as you though. I have the 27″ iMac bought mid 2010.

    Did you get the screen replaced?

    • nanchatte
      February 10, 2011 at 6:39 pm

      Yes I did, thanks for asking…. Here’s the deets…
      Mid 2010? You should still be covered by the original warranty.
      I think you still have a few months to make a claim… Remember that you can purchase AppleCare at any time within the first year of ownership…. I’m just going to pick up AppleCare on my iMac 27″ which Apple gave me on the 15th March last year as a replacement for my 2 year 9 month old AppleCare covered 24″ that Apple Japan were unable to repair to my satisfaction.
      I consider 48000 yen for 6 years of peace a reasonable (not cheap, though) investment for the shear beauty and functionality of my iMacs.

  2. Kees
    December 31, 2010 at 10:42 pm

    Did you ever solve this problem? I bought myself a new iMac 2 months ago, and about 1 month ago I noticed the same spots that you have. They might have been there since I got it, but I dont know. Also they dont grow, they are just placed on the left side of the screen..


  3. luca
    January 4, 2011 at 6:25 pm

    did you solve the problem? i’m starting to get those too!

  4. Rich
    March 25, 2011 at 9:51 am

    I am having the same problem but exactly one month ago today I had a previous screen replaced on my 27″ iMac. I think it may be a result of using a humidifier as I’ve seen this type of build up before and the new screen I received didn’t have this until now. Just appeared yesterday. It’s not the same pattern or in the same location but it’s the same thing.

    Do any of your guys use humidifiers? Anyway, I’ll call Apple again and get it replaced but it’s a serious inconvenience.

    • nanchatte
      July 12, 2011 at 2:20 am

      No humidifier here, but it’s as humid as hell in Summer.

  5. Diane
    April 26, 2011 at 2:25 am

    I am having the same issue on my 21″ iMac. I just bought it 1 month ago. And Yes, I have a humidifier in the room, it is on 24/7. Will contact Apple soon.

  6. June 22, 2011 at 12:09 am

    Here’s another one– big 8″ round spot in the middle of the 27″ screen…Just back after a month on the road and coming home to find this and update it from the powerbook is a pain…

    • nanchatte
      July 4, 2011 at 11:42 am

      Do you have any photos… I’d love to see them!

  7. Ryan
    July 1, 2011 at 11:29 pm

    im having the same problem but now after a few hours its starting to wear out but not completely and i have them on the left hand side of the screen.

    • nanchatte
      July 4, 2011 at 11:52 am

      Can you explain what you mean by “wear out?”

  8. Anonymous Steve
    July 11, 2011 at 1:39 am

    Same problem. iMac (mid 2010). I had the screen replaced under warranty by Apple Authorized Service Center in Netherlands in April. Now the new screen is showing dark patches in the top left corner several months later. I’m due for another trip to the service center this week. At this point I would like a guarantee that they will not replace the screen with the same batch of defective screens!

    • nanchatte
      July 12, 2011 at 12:00 am

      You know, I don’t think it’s the screen per se that is the problem. It’s more likely a fault in the overall iMac cooling design. I think it’s just a case of dust being sucked into the bottom vent by the fans and the finer grained stuff being deposited on/in the screens. Still, it renders an otherwise perfect machine useless every six months.

  9. July 24, 2011 at 11:37 pm

    I’m having this issue as well. I also think it’s the design of the iMac. I’ve had two screens replaced and now the 3rd screen is at about 25% blotch level of your image above. Now i’ll have to schedule another appointment. Have them keep my machine for 3-4 days and work from my laptop.

    • nanchatte
      July 25, 2011 at 12:18 am

      Tin, thx for the comment. Yes, it’s getting out of hand. There are so many reports now that I think the 27″ is fatally flawed. I’m going to sell mine a couple of months before the end of the AppleCare runs out….

  10. Alfred
    July 25, 2011 at 12:23 am

    Both the 27″ and 21″ are flawed. I’ve replaced my 21″ twice within the first year of owning it. Given that the blotches happened in the top right corner, the tech thought it was caused by environmental reasons (magnetism from power lines in the wall behind it, dust, or excess humidity). I doubt it.

    • nanchatte
      July 28, 2011 at 12:45 am

      “magnetism from power lines in the wall behind”


  11. November 30, 2011 at 9:01 am

    This is a very bad design flaw in the panel: the panel’s edges are not sealed, and dirt creeps between the polarizer (I think) and the lcd panel. Apple started recently to replace those screen (sometimes, when they can’t blame it on the user) with a new panel with sealed edges, but all owners of an affected iMac without a warranty are left out in the cold. This doesn’t seem right to me, since this is a VERY widespread issue, I started a petition to get Apple to recall the affected machines.

    Please sign and spread the word.

  12. Mike Lewis
    December 2, 2011 at 6:16 am

    Same here, I got 3 iMac 27″. Apple replace all 3 screen then everything was fine until now, winter is coming and we have started the ultra sonic humidifier, then boom the stain started to re appear. The iMac is not under apple care anymore, apple will not replace them and anyway it will not fix the problem. When we made them fix, Apple ask if we have Ultra sonic humidifier, I guess they know the problem, if you don’t have an ultra sonic humidifier, I guess it’s something in the environment that do the exact same thing

  13. January 30, 2012 at 6:19 am

    Come and subscribe here: http://www.dirty-screen.com/en
    We are 200 for the moment …

    • jstars
      February 19, 2012 at 3:23 am

      I went through two screens (under warranty) with my 2010 iMac 21″ when I was living in Europe. Humidity was high there. I moved to a very dry part of North America in 2011 and I haven’t had a single problem. It seems like environmental factors such as humidity play are a significant factor in this screen problem. That’s not saying that Apple is off the hook. These screens ought to perform properly across the gamut of temperatures and humidity one would reasonably expect customers to live in!

  14. Karl
    February 5, 2012 at 12:11 am

    Yep, that would explain it. This started happening to me about a week after I bought a new ultrasonic humidifier for the bedroom… I have a 27″ iMac, and it’s been perfect until now. As if a $50 humidifier just wrecked a $1600 computer. FML

  15. Phil
    May 31, 2012 at 3:01 am

    I have the same problem with my 21.5 inch iMac… no humidifier, house always between 68 and 75 degrees, and I live in California, so it’s not humid. Unfortunately, I didn’t get AppleCare when I bought it [about 2 years ago]. Am I SOL?

  16. Stewart luxton
    September 7, 2012 at 12:03 am

    Me too, stains on the screen, non smoker, clean environment!!!
    I discovered the stains the day after ordering the newer model for my mum, which I hastily cancelled( thankyou Amazon, great service) i took mine into the service today and wait to hear what Apple say. If this problem cant be solved long term , i will have to go back to PC!!!!!!!!!!!!!

  17. December 11, 2015 at 9:07 am

    I have the same problem too…unfortunately, mine is way beyond warrantee, so am SOL. Apple, you suck.

  18. John Butler
    December 12, 2016 at 1:43 am

    I also have an imac (2009) and use it, almost exclusively, for photographs. The “stains” on my computer are gray, wavy lines that make photo editing very difficult. Is the stain in the photo or is it just my defective screen? This has been a problem for a long time and I should have taken advantage of my warrantee. This problem is, obviously, a major defect in screen design and Apple should address it and correct it. I believe that a recall would be appropriate.

  1. November 25, 2010 at 11:30 pm
  2. March 15, 2011 at 12:56 am

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