HP-67 - need help to remove cleaning residue

[Geoff Quickfall]

I think you were lucky that the isopropanol did not remove the printing from the keyboard bezel. The printing was screened onto the bezel then sealed with a clear lacquer for plastic. The lacquer decomposes over time due to a chemical environment (lab) or UV exposure.

I have seen a mild soap solution remove the printing due to a badly decomposed protective lacquer finish. The best way is to dis-assemble the calculator. Remove the and clean the keys. Then with a VERY soft painters brush (not a nail brush, more like a make up brush) and a very mild solution of water and liquid soap (a few drops) wash the keyboard. Do not soak the keyboard. The process is to wet the keyboard, work the brush on the keyboard, rinse, repeat. On occasion the black background of the keyboard bezel will bloom in a filmy white. This is the decomposed lacquer remains absorbing water. It should diassapear with a thorough drying with a hairdryer.

To dry, do not RUB dry, only pat dry.

Never use a solvent and I include isopropanol or any anhydrous alcohol in that group. If required you can mask off the keyboard bezel along the chrome trim and display lens cover and re lacquer with a 'for plastic flat clear coat).

That will make the keyboard look and be protected to factory fresh standards.

Here Are some that I re-lacquered:







This HP 55 was missing the lacquer and actually I lost some of the printing from a mild wash as described:



I discovered the alcohol removal by accident on a Woodstock 25. I removed the word FIX SCI ENG with one swipe of a qtip. Never again.

With the above stated, some calc families have better more robust finishes from the factory then others.

Geoff