Mythbusting moisture-detecting stickers/liquid submersion indicators

There seems to be a fair number of myths surrounding moisture-detecting sticker or liquid submersion indicators (LSIs), so much so that I feel that a post is in order.
Written by Adrian Kingsley-Hughes, Senior Contributing Editor

There seems to be a fair number of myths surrounding moisture-detecting sticker or liquid submersion indicators (LSIs), so much so that I feel that a post is in order.

Since I love taking apart gadgets (both gadgets that are dead, and those that are still working) I've been coming across these stickers for years and have experimented with them a fair bit. I've also talked to many techies in the repair trade (both OEM and third party) about these LSIs and water damage in general. I've also successfully repaired many a drowned bit of kit.

Here's what you need to know about LSIs:

  • All but the cheapest electronic kit has one (or more) LSIs fitted.
  • Most LSI stickers are not stickers but tiny packets of dye (some are stickers with the a layer fo dye stuck onto the surface). The dye is normally white when dry but turns red when exposed to water.
  • The color change is not reversible through drying. Same goes for alcohol or bleach.
  • Liquids that contain water (such as soda, beer, tea, coffee, cleaning products, sweat and so on) will trigger LSIs.
  • LSIs are not triggered by high humidity, however, if that water vapor is allowed to condense then any water that condenses on the LSI will trigger it. Keeping a cellphone in a humid car overnight is enough to trigger one or more LSIs. A cellphone in your pocket might suffer the same fate.
  • Typically, cellphones have three fitted - one in the battery compartment, one on or near the charging circuit, and one on the mainboard.
  • Devices such as notebooks can have many LSIs fitted.
  • The LSI in the battery compartment is the one usually checked by cellphone store drones when a customer brings in a dead phone. However, while you might try to be clever and replace or remove that LSI, it's harder to get at the ones inside. On top of that, an expert can usually spot water exposure on a circuit board because it causes a subtle color change.
  • If you have a dead cellphone and the LSI in the battery compartment has turned red but you are convinced that the phone hasn't been submerged, insist that a repair center take a look at it - if the internal LSIs haven't been triggered, you may be granted a discretionary repair or replacement.

Here's what I do when I come across a soaked electronic device (these steps totally void the warranty, involve nasty chemicals and offer absolutely no guarantees):

  • The first thing I do is remove the power/battery as quickly as possible to prevent shorting (this is what causes immediate device failure).
  • The next step is to crack the device open for cleaning and drying. Cleaning is usually necessary because even if you manage to dry out the device so it works, corrosion attacks the circuitry. Sea water, soda and tea or coffee will definitely need cleaning.
  • To clean the device I use plain distilled or deionized water and irrigate the affected area. It seems odd of use water to clean water, but you are using clean water to wash off contaminated water.
  • To dry off the water I used a combination of silica gel in paper bags and lab grade acetone (which is great stuff because it dissolves water - but don't try this with nail polish remover because that actually contains a lot of water - along with other stuff - in the first place). I wash off the parts in the acetone (take proper precautions when handling the stuff - if in doubt, don't!) and placing the parts on the silica gel filled bags.
  • Next, leave the affected parts to dry naturally for 72 hours. A fan (not heater) blowing over the parts can help the drying process.
  • Reassemble and hope for the best!

Prevention is far simpler than the cure!

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