Restoration question


I bought an old HP-25 as-is from a surplus company. Luckily, it operated fine after I rebuilt the battery pack. The display area had some scratches, which I have been able to almost completely polish out using car wax. The plastic part of the case has all lettering intact, but the finish of the plastic is dull as if it were cleaned with an agressive solvent or something. Has anyone tried anything to restore the look of the plastic? This thing is slowly shaping up into a nice piece, and I'd like to keep going.

Also, the label on the front has a tear. If a reasonable approximation of the original artwork was available, I could get a new one printed at a print shop. Any thoughts?

best regards,


I've found that using a (small!) amount of car interior "enhancers" like Armor All will restore a nice gleam to older plastics.


Here is a thread from August about trying to brighten the case on a 97:

I don't know if these would help on the keyboard area, but there were lots of good clean-up tips in it.

As for having a new label printed, I think it would be cost prohibitive. The cost of making a silk screen alone would be in excess of $100 when you consider the camera work involved. There would be two images involved since the 25 label is 2 colors. You could make one screen with both images, but it would still be a two pass printing process. I would make a screen with one image on the top, the other on the bottom and just flip the screen over in the frame. Unless you have a friend in the business, or you REALLY REALLY wanted to restore the 25, I think the cost would be out of reach. On the positive side, the silver mylar would be no problem to source.

Then again, if you could find a 50 people that wanted a label at $3-$4 each, you might be able to do it. But then that would raise the issue of copyright since the Hp logo on the label is certainly a copyrighted image. Don't want to open that can of worms here (again).

Probably a lot easier to buy a dead 25 (read cheap) for the bits. You can always use the extra feet and spare battery for a Woodstock.


Unless you get real lucky, even dead HP25's ain't usually cheap... figure 25 bucks. More if it looks nice or even has the battery. Even more for case/charger/manuals.

A whole lot of them have label problems. The ink on the front label is prone to wear/wash off if cleaned with solvents. Also the rear label usually has a scratch across it where somebody pried out a stuck battery pack. It also invariably comes off wrinkled.

I checked my stash of dead Woodstock carcasses and all my front labels have been recycled for these very reasons. The ones that still have rear labels are all scratched, cut etc :(


Shows you what I know about Woodstocks. Not much. I owned a 25C until I threw it away a few years ago it a fit of rage when it starting returning answers valid to only 1 decimal place. Never knew you could kill the unit with the charger without batteries. I still regret it. :-(

I got to thinking about the labels and it might be difficult to reproduce the look. I don't think they were screen printed. While it would be the easiest way to create one, I think the originals where transfer printed. This is common on thin films. I think the clue is the thickness and the lack of durability of the ink. The ink is very thin with an offset or pad transfer process. A silk screened label would have an almost raised ink area and it would not have the gloss and flatness of the original label. So, I think they traded durability for the glossy look. This also precludes being able to touch them up. Would never have the same finish.

What we need is someone to find a pallet load of NIB 25C or 29C's in a warehouse somewhere...


A pallet-load of NIB 29C's . . . now you've done it. I'll dream about that tonight (sick, I know.) But I'll settle for the one which was taken off my desk years ago. I still keep the serial number, hoping some day it will find its way home to me - like the animals in those "Homeward Bound" movies!

About the labels - The one on the HP-25 in question is pretty glossy. The one on my HP-21 is flat. As you suggest, both are thin and look to be impossible to touch up.

Finally, on the plastic finish - the original is a nice matte finish. Armor-All and things like it give a glossy look. I'd prefer to keep the matte look if possible. Also, I have heard that some of these treatments look good for a short time, but actually contribute to long term damage because they attack the plastic. Any thoughts?


"stash of dead Woodstock carcasses" ? Any chance that I can get some of those ? I am looking for old calcs cases, for a project (developing new guts for old calcs). Keyboards would be nice also.


Unfortunately, I have been shuffling parts up and down the line as I have fixed other machines. What is left is all heavily engraved, cracked, melted, exploded, squashed, stripped, etc cases. All the keyboards I have left are broken, corroded, etc and totally unrepairable (beleive me, I'm not one to let a spec of HP go to waste).

I convert the crud into external battery charger units for 25C and 29C machines as I get them in. If I come across something that looks useable I'll let you know.


I use the Novus series of plastic scratch removers and polishes. They sell three different grades:

#3 - Heavy Scratch Remover -- It's a seriously abrasive polish that really removes plastic but works great on deeply scratched LED lenses.

#2 - Fine Scratch Remover -- If you're going to get just one of these get this one. It's great for getting out light scratches, cleaning any plastic surface and leaving a nice glossy finish.

#1 - Plastic Clean & Shine -- works well, just make sure that you work it into the surface and remove it completely; otherwise it sort of dulls the finish.

This stuff is pretty cheap if you buy from tanning bed supply houses (I guess that they get a lot of scratches!)

Try this one:


I found a place on Ebay that sells it in the larger bottles. They are a pinball machine supplier. I can't find their URL any more, but I bet they still sell on Ebay. Search for NOVUS. They sell the stuff directly or on EBAY with a reasonable Buy-it-now. I think one of each type in the (8oz?) bottles was $20 or so.


I have never heard of damage being caused by the standard "Armor-All" type products. The reason they don't last is that they are water based. So the water evaporates eventually, and you're left with the dull finish again.

One of my other interests is Soaring. We use a number of different products on the canopies of the sailplanes to polish the Plexiglas to a scratch free finish. Some of these products do have some micro-fine grit to remove scratches and liquid polymers to fill in the scratches. These would probably work well to "spruce" up the cases you mention.

The most common stuff we use that has been around for 20+ years, about $6/bottle:

M-1708 Mirror Glaze Cleaner

M-1008 Mirror Glaze Polish

Available here:

And a newer product that is even better, but more $$:

LP Acrylic Polish and Sealant

Available here:

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