Removing WP 34S overlay


After enjoying Version 2.x of the terrific WP 34S firmware on my HHC2008 HP 20b for about a year, I finally upgraded to 3.1. Wow!

However, now I need to replace the also-wonderful overlay (thanks, Eric!). The labels on the 20b keys peel off easily and without significant residue. The overlay on the calculator's face is another story. It has split and peeled, leaving a tremendous residue.

Any recommendations on how to clean it up so I can put the new overlay in place? I'm anxious to do it right - to get it clean without harming the case or internals, then put the new overlay in place so I can use it again.

Many thanks to all!


I used isopropyl alcohol and elbow grease to clean the reside off.

- Pauli



Most adhesives are based on some form of synthetic rubber and are easily removed with lighter fluid (the kind you use with, say, a Zippo lighter). Lighter fluid "usually" doesn't hurt stuff like car paint under it. But I have no idea what it will do to your 20B. I'd only use this as a last resort if the milder stuff doesn't work.

If you can risk it, test a drop on a Q-Tip on the back to see if it hurts the plastic before you go after the front. Keep it out of the key holes and away from the clear part over the display if at all possible.

Again, only as a last resort!

And things like toluene, MEK and acetone will undoubtedly ruin the plastic. Definitely don't go there!!!

My summer jobs during college years were at a manufacturer of self-adhesive papers, films and foils. Amazing what you learn when you're just a go-fer.

For those of you considering removing your WP-34S overlay, be careful to do the following for best results:

1. Pull away at a right angle to the surface; don't peel "back", but "up". "90-degree peel adhesion" requires the least force.

2. Go as slow as humanly possible. It's a "pressure sensitive" adhesive. You are applying "negative pressure" to peel the overlay. The force to peel cleanly depends on how fast you peel, but the force to break the plastic film is fairly constant. To avoid breaking, GO SLOW, thus keeping the peel force less than the tensile strength of the label.

Some adhesives are designed to be stronger than the substrate (film) they're on, rendering them "tamper evident" or "tamper-proof" as the film shreds without lifting the glue. Not much you can do with these. But I don't think that's what Eric used. Tamper-proof stuff is usually used for price stickers, labels on pharmaceuticals, stuff like that. Eric used a pretty strong, heavy label substrate. (Good choice -- easy to pick back up and realign if you start a bit off alignment, at least before the final "roll-down".)



Goo gone or goo b gone at the auto parts store works good for that. It is a citrus base adhesive remover.



Orange oil.

If you have a wax-based hair removal kit around the home then look for a small blue/green vial. It is a light oil that will also remove anything sticky.

After that use alcohol to clean up. It's easy and requires no hard rubbing. I use this frequently when restoring vintage tech--usually very sticky asset tags, etc...


Geez, guys. Hasn't anyone ever heard of WD-40?


Well, I used a wooden cuticle stick to push the remains of the label off the face of the calculator (firm enough to work, not hard enough to scratch) followed by cotton swabs with isopropyl alcohol to remove the glue. I used the latter instead of WD-40 or orange oil as I feared some might get down into the calculator. While the alcohol could do that too, it would evaporate.

The results were a nice, shiny HP 20b. Adding Eric's latest overlay resulted in a *stunning* "new" WP 34S. The overlays have gotten much better looking than the early runs a year ago!

Along with printing the Owner's Manual and Beginner's Guide, I feel like a youngster at Christmas. Thank you all, again!

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