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Chemical sanding method that will remove discolored ABS plastic

Started by TelePlay, April 05, 2018, 06:14:28 PM

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TelePlay

The following replies were split off of a restoration topic started by FabPhones in which she chemically restored a BT "Cowpat," otherwise known officially as a BT "Dawn" telephone, taking off the darkened, almost yellow discolored plastic, to reveal the phone's original color.

The following first reply was to support her efforts, showing that what she did does work to remove discolored plastic, but replies and questions and additional information added to the point the topic was hijacked by me and those posts would be better placed at the end of this topic, restoration of a age darkened WE 554, with another example of how chemical sanding works, this time on a 1961 WE light blue that had turned quite yellow/green.

TelePlay

Quote from: FabPhones on July 10, 2018, 12:11:43 PM
So, here it is, before and after pics of the cleanup using the acetone, acetone/meths, T-Cut, #5 polish method:

     Regular Member Post

That chemical mixture and technique does work and works faster than any other process should anyone want to try it. Opened a box to find a yellow/green WE 500 that is really light blue ABS plastics.

It is hard to take before and after images due to light differences so this before and after is of the housing after the discolored plastic was removed. The housing on the base with bezel and handset still discolored shows the dramatic change. The housing was the same color as the bezel and handset.

Not real shiny because the last step, when the photo was take, was that of the housing after it was made smooth with 600 grit wet sandpaper. But compared to the handset and bezel, it is easy to see the improvement chemical sanding makes to discolored plastics.

Took about an hour to do the housing so far and will take another hour of sanding up to 2000 grit and then polishing to a final shine.

Just another example to support the results FabPhones got with "The Cowpat."

andy1702

That's a good example of how well the colour change works John. It should be possible to get the shine back without any traditional sanding though. Here's a video of me doing the whole process chemically.
https://www.youtube.com/embed/0RCxChcycd4
Call me on C*net 0246 81 290 from the UK
or (+44) 246 81 290 from the rest of the world.

For telephone videos search Andys Shed on Youtube.

TelePlay

Quote from: andy1702 on July 14, 2018, 02:01:03 PM
That's a good example of how well the colour change works John. It should be possible to get the shine back without any traditional sanding though. Here's a video of me doing the whole process chemically.
https://www.youtube.com/embed/0RCxChcycd4

First, no intention here to hijack this topic from FabPhones. Posting here as additional information on the process FabPhones and Andy1702 use to remove discolored plastic.

I've watched your video, Andy, after doing my beige 554 and prior to doing this light blue 500. The problem I ran into with this light blue is that no matter what concentration of acetone solvent I used, what I cut it with or what material I used to remove the plastic, the removal process left a white haze on the plastic. I've seen this before. It is impossible to remove the haze without sanding. Other members who use acetone to remove discolored plastic have also told me they have seen this white hazing. Seems the light parts of the dissolved plastic is left on the surface and dries to a white haze. I don't know if you have seen the same thing. Each manufacturer in a time period use different plastics to make their colors. Each plastic reacts or responds differently to solvents. This haze is quickly removed with 400 grit wet sandpaper.

What I like about this process of chemical stripping is that a strong acetone mixture quickly takes the discolored plastic off. What I don't like about the process is that it can leave a white haze and the cloth used to remove the plastic never leaves the surface flat. Sanding with 400 grit wet sandpaper takes care of both problems, the haze is gone and the surface becomes flat.

If the surface is not sanded smooth, when finally buffed to a shine, reflected light will show the unevenness of the surface. The first image below shows the side of a beige 554 that was not sanded smooth. After final buffing, what should be straight lines in a reflection are irregular (red arrows). Sanding the side with wet 400 grit paper until it was smooth and then working up to 2000 and a final buffing shows the reflects line as straight, the bottom half of that image.

As I wet sand, I stop every 10 to 20 seconds and wipe off the wet dust with a rag. Looking at the surface with reflected light shows shows the areas on the surface that are still low and also the areas in which the discolored plastic was not removed (both very shallow plastic valleys caused by the cloth and discolored plastic not removed appear shiny in a reflected light). Using a cloth (rag or swab) to remove plastic with acetone does not, can never leave a smooth surface.

Usually, 97% to 99% of the surface after the first wet sanding with 400 grit is dull to reflected light allowing the low, unsanded spots due to the cloth plastic removal show quite well as mirror like, shiny spots or grooves compared to the 400 grit dullness. Sanding with 400 grit wet until the surface is completely dull indicates a smooth, flat surface that when buffed to a shine will show straight reflected lines.

Then, moving up to 600, 800, 1000 and 2000 wet papers using a 10% Acetone, 10% MEK, 80% Denatured Alcohol solution on a soft cotton cloth backed by a cotton ball to hold the solvent on the plastic between each grit greatly speeds up or reduces the time it takes to get to 2000 and then buffing. Sanding with each grit takes only a half minute or so before wiping the residue off and going over the area with the DA mixture getting it ready for the next grit. The DA mixture "softens" the ABS allowing the next grit to work faster than just wet paper alone.

After the 2000 grit is used, I wet the surface with the DA mixture and while damp, put Novus 2 on the mixture swab and cover the side being worked on with Novus to keep the DA solvent in contact with the plastic, adding more Novus from the bottle to make sure the Novus stays wet. I then remove the wet Novus with a Ryobi orbital buffer using a Terry Cloth bonnet (micro fiber and wool bonnets do not work, I tried them - something about the "roughness" of the terry cloth give the best buffed shine). The combination of the DA mixture in the Novus really helps buff the surface to a nice shine.

I then do two applications of Novus without the DA mixture and buff them off while the Novus is wet with the Ryobi. I did the complete handset and caps this morning in less that a half hour, from stripping to sanding smooth to sanding up to 2000 grit and finally buffing.

The thought of sanding plastic scares some but with the use of the solvent mixture between grits and with Novus, removing discolored plastic (which looks ugly at that point) and taking it to a nice, flat shine is quite easy to do. Here is the after of the light blue 500. Prior grit sand marks do not show if the DA mixture is used between grits and the next higher grit is used equally over the surface in a random motion.

If some want to go to 2500 grit or higher to get an even better shine, that is there decision. I find 2000 with Novus leave the surface looking better than the phone when removed from normal service. My intention is not to produce a glass mirror shine with absolutely no usage marks like those posted by Jorge.

The light blue before and after in the second image is an example of my sanding to buffing process after chemically stripping discolored plastic from a phone housing, handset and bezel.

Finally, all of the above is a lot easier to do that to put into words and read. The learning curve is quite steep to anyone who want to try this.

FABphones

As usual Teleplay, nicely explained with enough detail so we can try it for ourselves.

Thanks for adding to this thread. Beautiful work.
A collector of  'Monochrome Phones with Sepia Tones'   ...and a Duck!
***********
Vintage Phones - 10% man made, 90% Tribble
*************

TelePlay

I should have mentioned that all sanding MUST be done with a sanding block to get the surface flat. Hand sanding with finger tips will not work, that will just create waves in the surface.

When I realized the solvent on cloth was creating an uneven surface, I made a small sanding block out of wood with a 1/4" Shore A 60 rubber backer on the sandpaper side. That worked well on flat surfaces but did not handle curved areas well - too hard, not flexible.

Thanks to Pourme, I tried these sponge center sanding blocks (images below). Walmart has one that is 400 grit on one side and 600 grit on the other, just perfect for what I was doing, getting started after the discolored plastic was chemically removed. While Walmart did not have any higher grit blocks, I did find 1000 and 2000 grit sponge center blocks on Amazon. But, one can simply wrap a higher grit sandpaper around one side of the 400/600 block. That works well for moving up to 800, 1000 and 2000 grit levels.

These blocks can be cut to make a width that is a bit smaller than the distance between the ears/hand hold on a WE 500. That leaves 75% of the block whole for sanding.

What's nice about these is that the sponge is firm enough to sand a flat surface smooth but flexible enough to handle the round edges, sand them smooth without creating waves. They contour to the roll on the front of a 500, the back side role, the corners, the ledge below the ears on both sides of the housing and the slightly concave bezel.

Sanding without a sanding block will never result in a flat surface and these sanding blocks because of their size, cover a large area making sanding a side a quick process.

Pourme

Another fine job, John. I love how those blue phones look when they are done right.

Those sanding sponges really work well.They speed up the process while saving the fingers, Too!
Benny

Panasonic 308/616 Magicjack service

Doug Rose

WOW! What a transformation. It doesn't get any better than this.....Doug
Kidphone

TelePlay

First, the above replies dealing with the WE light blue 500 restoration have been split off of FabPhones "Cowpat" restoration topic so as not to have hijacked that topic.

This reply adds other set of before and after images and information on how the handset cord was improved.

The first image shows the phone, on the right, with the handset cord reinstalled. While it is still a bit yellow, the handset cord is much closer to blue than it was before starting. The cord was removed and the coils cleaned with a cotton cloth soaked with the 10% Acetone, 10% MEK, 80% Denatured Alcohol mixture. I discovered this mixture works fast and well to remove both crud from cords, be the crud dirt, oil, or tar. I used to soak in soapy water but found that did not remove stuff that was not water soluble and the mixture did, and without water cleaning first.

Once the cord was cleaned, I put it into a glass jar (actually, a Grandma's Molasses jar left over from another hobby works nicely for a normal handset cord) and filled it with Volume 40 Creme Developer (available from Sally Beauty Stores for $3.40 in a 32 ounce bottle). The molasses jar with the cord inside used a bit less than half of the 32 ounces.

I stirred the cord by lifting it up and down and using a metal rod to swirl the cord around in the jar every hour or so to keep the developer in contact with the cord fresh. I let it soak in the peroxide creme for 12 hours. It did not completely remove the green/yellow color but after treatment, a good 75% of the color was gone and it looked more blue than green. I left it in the developer another couple of hours but no improvement was seen. A good point of comparison is the cord where it enters the retention nipple at the handset.

Going back to the need or use of sanding, the second image below shows the housing before and with half of the discoloration removed from one side. On the left side of that image, two red circles show dings in the plastic. The insert in the upper right corner of that image shows that sanding the plastic after chemically removing the discolored plastic has removed those dings. That same image has a yellow circle showing the white haze that shows up on some plastics when discoloration is chemically sanded, removed, from the surface (the right side of that image has been sanded but not polished).

Chemically removing discolored plastic followed by sanding to get a flat surface is a fast all-in-one technique that gets the original color back and in the process, removes minor dings and scratches from the plastic.

andy1702

I have indeed seen the white haze Teleplay talks about. It's interesting because it only happened during some restorations but not during others using the same technique. From my observations it only seems to appear once the meths has been added to the mixture, So I suspect it may be something in the meths reacting with either the plastic or the acetone. I'm planning to experiment with something else to cut the acetone. Simple water might even do it.

I think the polishing technique also has something to do with the haze. I certainly didn't experience it while restoring the phone in my video, but I got quite a bad haze on a dark blue phone I'm currently working on. I thought it was something contaminating the surface rather than part of the plastic itself. I could be wrong though. I'll report back when I've tried a few things.
Call me on C*net 0246 81 290 from the UK
or (+44) 246 81 290 from the rest of the world.

For telephone videos search Andys Shed on Youtube.

TelePlay

Quote from: andy1702 on July 19, 2018, 06:50:38 AM
I have indeed seen the white haze Teleplay talks about. It's interesting because it only happened during some restorations but not during others using the same technique. From my observations it only seems to appear once the meths has been added to the mixture, So I suspect it may be something in the meths reacting with either the plastic or the acetone. I'm planning to experiment with something else to cut the acetone. Simple water might even do it.

I think the polishing technique also has something to do with the haze. I certainly didn't experience it while restoring the phone in my video, but I got quite a bad haze on a dark blue phone I'm currently working on. I thought it was something contaminating the surface rather than part of the plastic itself. I could be wrong though. I'll report back when I've tried a few things.

Yes, some plastics do not haze, other do quite severely.

There are two things going on, the composition of the plastics (they melt white pellets with colored pellets to get the color they want) so it might be the white plastic being more soluble in acetone and as such staying on the plastic in the acetone that dries on the surface (a thin layer chromatography plastic separation thing where the darker plastic stays in the cloth and the lighter plastic stays in the acetone and becomes a white paint like liquid) OR the white haze is nothing more than acetone dulling the surface, causing a blush, the same as having a drop of acetone land on a plastic and evaporating to leave a lighter colored, dull spot.

By definition, different colored plastics are not chemically the same and acetone, or other solvents, will interact with each colored plastic differently. The proof of that is discolored plastic is much harder than the original plastic and when removing it with an acetone mixture will feel like glass until the discolored plastic is removed and then the underlying original, softer plastic is more quickly dissolved with the acetone mixture and the cloth being used to remove the discoloration will grab the original plastic, feel sticky or tacky - a good indication that the discolored plastic is gone when rubbing the solvent over the surface.

On one side of a phone, one end may be more discolored than the other due to how the sun hit the plastic. In my experience, it takes longer and more pressure and more solvent to get the darker color off. A good example of that is the highly discolored chips from my toasted ivory 302 that have now been soaking in pure acetone for a few months are are still not dissolved - the discoloration chemical change made that plastic rock hard.



I don't fully remember what water with acetone did but I seem to remember it may have beaded up on the surface rather than stayed smooth as the alcohol did. I did try mineral spirits as the solvent but acetone is not readily soluble in that organic solvent, an oil and water thing.

I've even seen the white haze on black plastics but only when the acetone concentration was high so it might just be a blushing issue.

Let us know what your experimentation discovers or determines.

FABphones

Quote from: andy1702 on July 19, 2018, 06:50:38 AM
.......I'm planning to experiment with something else to cut the acetone. Simple water might even do it.....

Andy, if you want to cut the Acetone, rather than water what about trying a manicurist Acetone. I've tried it. It mixes well but is none effective in dissolving ABS so would dilute the proper Acetone quite well if that is what you are looking to do.


ETA: I have several bottles of this so since writing the above I thought I'd check the ingredients against each other. No two bottles contain exactly the same. Besides 'Acetone' I also have 'Acetone free'. The Acetone free version is the type used to remove false fingernails. I tried both types on ABS.

None of the four or five bottles I have made much (as in negligible) or none of a difference. But do a hidden test patch first if you want to try this, yours might contain yet another set of ingredients. It should be noted that none of these manicurist products I have actually contain any Acetone. I'm guessing the name is just a throwback to when they did, but it can get confusing all the same.



A collector of  'Monochrome Phones with Sepia Tones'   ...and a Duck!
***********
Vintage Phones - 10% man made, 90% Tribble
*************

JimNY

I have tried this technique a few times with improved results each time. One thing that I haven't been able to figure out is how to restore the embossed logo on the handset. The first try left the logo 'muddled' as the acetone dissolved the top layers of discolored plastic.  I'm starting work on a numbers matching pink princess dated 1960 that is badly faded. Does anyone have any tricks on how to restore color to this sensitive part of the handset?

Thanks in advance!

TelePlay

The choice is to avoid the emblem and leave it a perfect but discolored emblem OR remove the discoloration and end up with a muddled to mostly removed emblem.

No way to sand discoloration off of the letters with either paper or chemical without removing the emblem lettering itself.

TelePlay

BTW, the hardened ivory soft plastic chips shown soaking in pure acetone in Reply #25 have still not dissolved. They have been soaking in pure acetone for about 2 1/2 years now.  All I've done, a couple of times, was to add more acetone which slowly evaporates out through the cap threads.