The sticky HP 35s plastic case

[McGruff]

I am new to the forum. I had removed my HP 35s from storage and was disappointed to find that the rubberization of the case was going bad. It became sticky, tacky, gooey, and rubs off. I have experienced this on sports and optical equipment before.

Soaking denatured alcohol into the material loosens it further. Using a plastic scraper, toothbrush, and paper towels, I was able to remove the rubberized material completely. I didn't know how it would look later, but it turned out well. Underneath, the case is covered with a cloth-like covering.

I figured this information could be useful to someone someday.

[rprosperi]

Interesting!! I've seen many posts start off that way, but have never seen the unexpected sharp turn towards exploring how to make lemonade from the lemons one was dealt. When (not if...) mine starts to peel, I'll do the same thing, it looks a lot nice than the flaking death of leaving it as-is.

I wonder if the 33S case has a similar surface under it's fake leather-like coat??

[Steve Simpkin]

Interesting. My HP 35s has the later slip case, similar to the one that came with my HP 33s. For some reason, the black finish has flaked off in tiny pieces on the edges and flexible sides of the HP 35s case. This occurred during storage and is still happening. The HP 33s case, while older, still looks like new.

For reference, here is Didier Lachieze's PDF document that has pictures almost every known case supplied with various models of HP calculators over the years.
https://www.hpmuseum.org/forum/attachment.php?aid=9780

[McGruff]

I wouldn't expect any leather-looking cases to have the same results. This rubber-like material was used heavily for tactile reasons. Binoculars and scopes. I had the same garbage go bad on a shifter. If it was made to feel tacky, it could be the same material, and eventually it could begin to break down.

It's unfortunate that HP started using cheaper materials. The cases for both of my HP 11c's are in great condition, and are decades older. Well, the difference with the HP 35s itself is apparent too.

Great link Steve! Fun to see those cases and holders.