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HP-67 - need help to remove cleaning residue
02-29-2016, 12:35 AM
Post: #1
HP-67 - need help to remove cleaning residue
Hi folks,

I have an HP-67 that I'm trying to clean. I used some Isopropyl Alcohol and a q-tip to clean between the keys and in other areas. Now there is some residue there that I can't seem to remove. See photos. Can anyone recommend a way to get it off? Thanks,

Ed

[Image: IMG_2648_zps9dldtnfj.jpg]

[Image: IMG_2646_zpsvisc5evx.jpg]
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02-29-2016, 04:04 PM
Post: #2
RE: HP-67 - need help to remove cleaning residue
I think what you are seeing is not a residue but the result of removing oils from the plastic. I use small amounts of a high-quality liquid furniture polish without wax to clean calculators as this seems to be better for the plastic. I don't know which country you are in, but here in the US we have Scott's Liquid Gold, which is what I use.

David Brunell
Houston, Texas
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02-29-2016, 05:45 PM
Post: #3
RE: HP-67 - need help to remove cleaning residue
I also think that it can be residuals from the cleaning. Perhaps a new cleaning cycle with the isopropanol can remove it.

C├ęsar - Information must flow.
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02-29-2016, 06:48 PM (This post was last modified: 02-29-2016 07:05 PM by Geoff Quickfall.)
Post: #4
RE: HP-67 - need help to remove cleaning residue
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:

[Image: hp35.jpg]

[Image: hp67.jpg]

[Image: hp65.jpg]

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

[Image: hp55.jpg]

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
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02-29-2016, 07:51 PM
Post: #5
RE: HP-67 - need help to remove cleaning residue
Hi folks,

Thanks for the suggestions, especially Geoff. Your cleaning process works wonders. Those calcs look great.

quantalume,

I'm in California. I'll pick up some Scott's liquid gold next time I'm at the store

Geoff,

I'm not confident that I'd be able to take one of these calcs apart completely without risk of breakage.

Ed
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02-29-2016, 08:04 PM
Post: #6
RE: HP-67 - need help to remove cleaning residue
I would hold off on the liquid gold. It does contain natural oils which are also sovents especially if left on to long.

The reason some people have success is that the lacquer finish is still intact, or the family of calcs they are restoring have a robust finish. Woodstocks are notoriously less resilient to cleaning. Coconuts can withstand a lot of physical cleaning and of course the pioneers, voyagers with metal overlays withstand a lot except for sand paper!

I tried Armorall for car plastics and removed the printing on a Woodstock. Stick with soap and water or if you are afraid of diassembly a q-tip and soap and water, not oils, cleaners and etc.

The best is to diassembly, here is a 45 that was done:

http://www.hpmuseum.org/cgi-sys/cgiwrap/...ead=131014

Geoff
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02-29-2016, 09:03 PM
Post: #7
RE: HP-67 - need help to remove cleaning residue
(02-29-2016 08:04 PM)Geoff Quickfall Wrote:  I would hold off on the liquid gold. It does contain natural oils which are also solvents especially if left on to long.

The reason some people have success is that the lacquer finish is still intact, or the family of calcs they are restoring have a robust finish. Woodstocks are notoriously less resilient to cleaning. Coconuts can withstand a lot of physical cleaning and of course the pioneers, voyagers with metal overlays withstand a lot except for sand paper!

I tried Armorall for car plastics and removed the printing on a Woodstock. Stick with soap and water or if you are afraid of diassembly a q-tip and soap and water, not oils, cleaners and etc.

Geoff

I strongly agree to Geoffs advice. Don't use Isopropylalkohol or other solvents. I wiped the PAUSE label off one of my HP-25 some years ago and was shocked about my stupidness. I think you should not share the same experience.

For HP-29C there is at least an overlay available, which restores the printing, but cannot make it original again. I don't have experience with HP-67 because now I'm very careful with cleaning at all.

Bernhard

That's one small step for a man - one giant leap for mankind.
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