What Are Pressure Marks on a Laptop?
By John Lister
A pressure mark is a sign of physical damage to the inside of an LCD screen. It is related to, but not always synonymous with, the problem of dead or stuck pixels. Usually it is not financially viable to repair pressure marks.
LCD Screen Basics
Virtually all laptops have a liquid crystal display screen, mainly because the technology lends itself to light and thin screens. LCD involves shining light through a sheet of crystals which combine properties of a solid and a liquid. These crystals are red, green and blue and can be electrically controlled to be "on" (meaning they let light through) and "off" (meaning they block light.) The combination of the different colored crystals across the screen being either on or off and the backlight passing through creates the colored image on the screen.
A pressure mark is where physical pressure on the screen has led to the layer of crystal being crushed between the two layers of glass that surround it in the screen. This could cause crystals to lose either their liquid or solid properties, meaning they can no longer be manipulated by the computer to act as a filter for the back lighting. Another problem is that the crystal may be pushed out of position, for example by being twisted or rotated. These forms of damage may be visible in the screen by showing the wrong colors, or the image may be blurred or distorted, looking a little like if a drop of water fell on a painting that hadn't yet dried.
Stuck and Defective Pixels
A stuck or defective pixel is a specific problem with a laptop screen. It may be a symptom of the damage that caused a pressure mark, but may also be the result of unrelated problems such as electrical failure. A stuck pixel is one in which at least one of its three sub-pixels (which are colored red, green and blue) remains permanently on or off, meaning the pixel will often appear to be the wrong color. A dead pixel has all three sub-pixels permanently off, meaning the pixel is continually black. The fact that pixels are extremely small means that most pressure marks will involve numerous pixels being affected, whereas other causes can lead to a single pixel being dead or stuck.
Preventing Pressure Marks
To reduce the risk of pressure marks, avoid pressing or holding the screen wherever possible (unless of course it is a touchscreen, which is designed for such pressure.) Take particular care not to press down when wiping the screen. When transporting the laptop, make sure it is securely closed and that you have not left any objects such as a pen or a magazine between the keyboard and screen.
Dealing With Damage
Some online resources claim the ability to fix dead or stuck pixels through techniques such as repeatedly flashing the screen dark and light. While the success of these techniques is debatable, they are not relevant to pressure damage as they are attempting to fix an electrical fault. Pressure marks are a sign of physical damage which cannot be undone without physical attention to the layer of crystals -- and even this is not a guaranteed fix. As physically dealing with the crystals involves taking apart the laptop screen -- a tricky and intricate task -- it is rarely if ever economical to fix a pressure mark compared to replacing the screen (if that is possible with a particular laptop) or replacing the entire laptop. If you do get a pressure mark on your screen, generally you will have to decide if the visual annoyance outweighs the cost of replacing the screen or laptop.
A professional writer since 1998 with a Bachelor of Arts in journalism, John Lister ran the press department for the Plain English Campaign until 2005. He then worked as a freelance writer with credits including national newspapers, magazines and online work. He specializes in technology and communications.