Removing hard glue from HP-28S?



I recently got a 28S. It is in good condition except some glue in the cover. It is very hard glue, not like from textile band. The glue is above the alpha-keypad and covers the onprinted documentation.

Do you know any good method of removing such glue without damaging the calculator? I tried to cut it away with a knive, but only some sand-like parts came off. How durable is the printed documentation in the cover? Can I continue scraping on it and try several chemicals or better not?

Are there any chemicals which soften the glue but not the calc?

A bit of the same glue is on the calculators backside. Because of the bumpy surface there, it will be impossible to mechanically remove the glue without removing some of the calculators plastic. What could I do here?

Thanks for any advise...




I tested an "all-glue removal" once, from Loctite, the same co. that produces SuperBonder. I still have it, and it is composed by Propylene Carbonate. Maybe you can find it easier, because I bought it in a small supermarket. Also, all inscriptions are in Portuguese, so I do not have the original names in English, just the translations.

Unfortunately it not only dissolved the glue (SuperBonder) but also melted the plastic where it was. Anyway, if I understood it well, your HP28 has glue over the upper left-shell, the one with the ALPHA keyboard, where you read some information about the different object types that the HP28 can deal with, right? This printed portion of the shell is protected by a rugged, transparent coat (acetate?). MAYBE this material is not melted by the all-glue removal, you should try. The worst is that I am not sure about what material is this protective coat made of, so you could test it before using in the calculator itself.

If you have any success, let us know, please.

Best regards.


I have found that Coleman camping fuel (white gas, cigarette lighter fluid) works very well ad removing most adhesives, paint residues, and sticky gunk from calculator cases. It does not seem to affect the case or labels. I can leave some "water marks" on the keyboard backgrounds.

Also strong (91%) isopropyl alcohol works well. Unfortunately it can cause some clouding of clear display windows (which can be cleaned off) and on a few labels it can remove the ink. Whatever solvent you try, first test it in a hidden area.


Thanks for your hints so far. Until now I tried everything I found at home but no success. (desinfection spray, terpentine, Isopropyl, lighter-gas, barbeque-grill-cleaner, rust-solver... I will buy some aceton next week.

By the way - the HP28 is very durable! The above chemicals did not damage it. (I wouldn't try that with a more valuable calc of course!)

Maybe I should burn it off? ;-)



DON'T use acetone. It will definitely remove the label paint and damage the plastic.


I'd say the same about acetone! Do not use it. Definitely will damamge the painting (even the cover) or leave watermarks. (cloudy white spots)

But burning it out? Oh, boy! ;-D


Hello David and Luiz,

UH, thanks for your acetone-warning! I will let it in the shop. Maybe it is the best to leave the calculator as it is.

I have another HP-28S without glue, but with a broken battery compartment. Maybe I'll try to exchange some parts between the two.


Possibly Related Threads…
Thread Author Replies Views Last Post
  How to copy files from 9114B to hard drive via PIL-box? Joe Horn 23 10,263 12-14-2013, 11:57 PM
Last Post: Geoff Quickfall
  Riemann's Zeta Function update (HP-28S, HP-48G/GX/G+, HP-49G/G+/50g) Gerson W. Barbosa 0 1,066 06-30-2013, 01:01 AM
Last Post: Gerson W. Barbosa
  Riemann's Zeta Function (HP-28S) Gerson W. Barbosa 8 2,601 02-03-2013, 03:23 PM
Last Post: Gerson W. Barbosa
  HP85B and 9133H hard drive Roe Peterson 6 2,062 12-20-2012, 10:17 AM
Last Post: Juergen Keller
  28S Pi Functionality Matt Fegenbush 3 1,550 10-17-2012, 02:15 AM
Last Post: Nick_S
  Glue for HP42S bezel Basil 0 820 08-08-2012, 12:23 PM
Last Post: Basil
  HP-28S plays "Happy Birthday" Kevin F 0 1,045 08-06-2012, 04:53 PM
Last Post: Kevin F
  HP-28S Mathematical Applications manual errata Tom Sauntry 2 1,352 07-25-2012, 09:54 AM
Last Post: Tom Sauntry
  HP-28S Syntax Errors William N Strew 7 2,553 07-15-2012, 05:09 PM
Last Post: Luiz C. Vieira (Brazil)
  Removing WP 34S overlay Jim Horn 6 2,129 06-29-2012, 07:26 PM
Last Post: JimHorn

Forum Jump: