How-To Geek

Use Packing Tape to See Through Privacy Glass [Geek Tricks]

From the weird science files: you can use a simple piece of tape to create a clear peep hole in frosted privacy glass. Check out this video to see it in action and read on to hear how it worked in our informal test.

In the video above YouTube user TheFarmacyMan shares an interesting video demonstrating a trick he stumbled upon accidentally–if you put clear tape on a frosted privacy window the tape acts as a peep hole through the glass. He has no explanation for the effect but one of the commentors suggests that perhaps the adhesive from the tape fills in the texture of the frosted window (most privacy windows are acid etched to create the “frost”) and in doing so makes the frosted glass more like the original smooth glass it was before the frosting solution was applied.

Because we’re painfully curious, we had to see if this trick would work on the frosted windows around the office. We had two windows we could test, a window in a bathroom that had been professionally frosted (it came from the window factory acid etched) and a window that had been “frosted” by being sponged with acrylic glaze to create a simple DIY privacy glaze. Although fully braced for the trick to not work, we were shocked when it worked on both windows. It didn’t create a perfectly clear portal through which to peek but it provided enough clarity that what were just blobs outside the window became easily identifiable as trees, cars on the street, the mailman coming up the sidewalk, and other features of the landscape. Consider us extremely impressed by how effective a simple piece of packing tape was rendering the privacy glass less private.

Weird Tape Effect [YouTube via BoingBoing]

Jason Fitzpatrick is a warranty-voiding DIYer who spends his days cracking opening cases and wrestling with code so you don't have to. If it can be modded, optimized, repurposed, or torn apart for fun he's interested (and probably already at the workbench taking it apart). You can follow him on if you'd like.

  • Published 04/25/11

Comments (30)

  1. Hatryst

    Time to replace the bathroom door…

  2. Lucas

    Its work both sides? or only on the side the tape is?

  3. Jason Fitzpatrick

    Lucas: The effect appears to work both ways, assuming the glass is only frosted on the side the tape is applied to. I went and taped the office window again just to test it to answer your question. You can indeed see in, as easily as you can see out, in the spot where the tape is. The big difference would seem to be this: When you’ve taped the inside and are looking out your eye is usually close to the spot you taped so you have a clearer view with a large field of view. From the outside in–say from the street–all you see is an little tape size spot on the window where the frosting seems clearer than the rest. Unless the person walked right up to that spot and looked in like a door peep hole they couldn’t really see much.

  4. grrr

    also works with spit

  5. Michael

    It seems to me the easiest way to defeat this is to frost both sides of the glass.

  6. wot?

    epic…cool…but how many perverts will use this exactly?

  7. Hatryst

    “Here’s how I think it works, if anyone cares. The glue on the tape fills in the small imperfections on the surface of the glass. Since the glass, the glue, and the tape are clear, filling in the imperfections (the frosting) makes the glass clear.”

    Via Youtube

  8. Lady Fitzgerald

    Glass that is frosted on only one side is safe from this trick as long as the frosting is on the private side.

  9. Mon Sewage

    mmmmmmm…. frosting….

  10. Brad

    Hatryst has it partially right. Etching glass causes small inclusions. These inclusions diffuse the light when it hits them, or passed through them, kind of like setting a garden hose to mist. When you add the clear tape, the light is no longer being diffused, it’s still slightly blurry because of the etching and glue.

  11. grrr

    Oh, but hatryst got his info from YouTube, it therefore MUST be correct

  12. Hatryst

    Yeah, right :D

  13. Anon

    well kipkay is gonna steal this

  14. Anon

    according to the highest rated youtube comment
    “Here’s how I think it works, if anyone cares. The glue on the tape fills in the small imperfections on the surface of the glass. Since the glass, the glue, and the tape are clear, filling in the imperfections (the frosting) makes the glass clear”

  15. Brad

    It has nothing to do with the glue filling in the “imperfections”. When ever light enters of leaves a medium, it’s path is determined by it’s surface. When the surface is etched, the light traveling though the glass gets scattered when it exits. The light coming in contact with the etched surface is scattered before it travels through. Smear all the glue you want on there, if you don’t have a smooth surface it’s still going to scatter the light. Pour water on and it will have the same effect because the water creates a smooth surface (through surface tension) for the light to enter/exit from.

    Look up some basic physics regarding light and how it travels through glass.

  16. Bob

    Easy enough to test brad’s theory–try the trick with a clear piece of cellophane or Saran wrap

  17. pandaSmore


    I hope you replied to the top rated comment on YouTube.

  18. pandaSmore

    Hey everyone this is how it works!

    “heres the most obvious answer im surprised no1 else has put up, ummm, what about his finger? if its frosted, then his warm finger just heated up the frosted glass therefore making it clear, i could do this without tape >.> If you pay attention, it only gets clear where his thumb pushes down, not when he actually puts on the tape. Use some object to push it down that doesnt have a internal temperature as a human, then ill be impressed……..”

    I’m sorry if you lost any brain cells, but that was just too funny to pass up! I love YouTube.

  19. Scott

    Brad is right. If the light is not interrupted or scattered as it travels through a surface then that object is clear the more scattered light is as it travels through the glass the more opaque the glass is, the tape acts as a bridge for the light.

  20. Martik

    Now I can see when my boss is coming! >>> BOSS FAIL!
    wait a minute, he will see me too!

  21. Omar

    “Now I can see when my boss is coming! >>> BOSS FAIL!
    wait a minute, he will see me too!”


  22. Khalid

    This is one amazing discovery :)

    I too believe that the tape ‘fills’ in the gap thus smoothening the surface, and as result, opening up the view.

    And if this theory is right, double-sided frosting should also reveal the objects on either side if taped on both sides.

    The solution? Hmmm… I guess it’s best to use those tinted stickers that will just block out the view. Not the same finish though.

  23. ShiningStar

    Try with water when cleaning frosted glass you get the same effect as the tape..

  24. KenLV

    FYI it WON’T work is on glass with the privacy “film”. Looks like the cheaper option also turns out to be the better one!

  25. Bryan

    Ok thats 10 minutes of my life I won’t be getting back

  26. Karl

    I love the internet!
    Best laugh today.

  27. ose

    and from the other side is there any notice of the peek a boo?

  28. Phill

    First I tried pouring water over the window, all the water ran off and got my socks all wet – then I tried Packaging tape, but I couldn’t see through that, then my wife came out of the Bathroom and belted me with a can of hair spray for trying to perv on her….had to mop up the water on the floor – had a bugger of a day.

  29. Thinker Bell

    Son of a gun, it worked. I told a friend about this and he tried to use “invisible” tape which is “frosted” itself, and of course, it didn’t work. It just has to be clear tape like the clear Scotch tape.I imagine that there are practical uses for this but I can’t think of any at the moment. Thanks for the video!

  30. RogerJ

    Doesn’t work on my frosted bathroom window, which is double-glazed!

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