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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

One more way to restore discolored plastic. Others have their methods and end up with well polished, original colored housings. This is one more technique or method that can be used to remove scratches or dull surfaces resulting in a nicely polished surface.

After trying everything from wet sanding to bleach to peroxide, I am a firm believer that the only way to really restore faded or discolored plastic is to remove the discolored layer. Chemical treatment to re-arrange surface molecules into something near their original properties required to absorb and reflect specific wavelengths of the visible spectrum to produce a desired color is an imperfect solution to restoring discolored plastic. The only real solution is to remove the top layer of degenerated molecules and expose the original plastic with the original color which lies just below the surface. There are no short cuts or quick fixes to correctly restore the original color, except this one, chemical sanding to remove the top, discolored layer.

Based on the pioneering chemical sanding work done by cihensley and recently modified by WEBellSystemChristian, those efforts were the basis for developing this technique to quickly remove discolored plastic from ABS plastic.

This technique ONLY applies to ABS plastics
IT WILL DESTROY TENITE OR SOFT PLASTIC

A technique for discolored Tenite or soft plastic is in the works and will follow in time.

To demonstrate this technique, a discolored beige (darkened) WE 554 housing was used. This housing was darker on the right side and right front than the left side and left front. The entire housing was discolored so some extent. The left slightly darkened side was use to demonstrate this technique. The darker side would take longer (more plastic to remove) and the front is complex due to the dial cut out and the emblem. The left side is a continuous, flat surface well suited for the demonstration. This side had no major scratches, just very minor surface makes from years of use. These age marks were removed along with the discolored plastic in this technique.

The technique is reversible in that at any point in the process, if something is seen that should have been removed, it is possible to go back to the step where it should have been removed and start again from that point and move forward to a final, original colored, nicely polished surface.

The first step is to wrap the high bite cloth around a cotton ball and soak it with pure acetone. The swab is moved continuously and quickly with heavy pressure all over the side. Do not allow acetone to pool in any spot and DO NOT stop moving the swab on the plastic (that will create a mark that may require sanding to remove).

The acetone will begin to peel off the top discolored layer of plastic. As the high bite cloth picks up this plastic, the swab will begin to feel smooth (filled with plastic) and lose its bite. Toss that swab and begin again with a new patch and cotton ball soaked with acetone. Do this over and over until all of the discolored plastic is chemically sanded off of the surface. You will notice that the top, discolored plastic layer feels slick or harder or smooth and after it is removed, the original color plastic will have a bit of a sticky feeling as the swab passes over it. Keep working on the "slick" areas but use uniform strokes over the entire area to prevent marks. Some colors are easier to see being removed (yellowed plastic of an aqua 500 for example). This beige housing is a bit harder to see but it is possible to see the old, hard plastic as the swab works to remove it from surface.

When the surface seems to be color uniform, the original color, use one last new high bite cloth and cotton ball  with acetone to "smooth" out the surface, to make it as even as possible with the acetone swab. Use a center on to off the edge stroke to get rid of cloth marks.

The next step is to use a high bite cloth and cotton ball with a solvent mixture of 5% Acetone, 5% Methyl Ethyl Ketone and 90% Denatured Alcohol to go over the surface, with medium pressure, to smooth out any marks left by the high bite cloth. This mixture will remove very little plastic, it acts as a chemical polish.

Next, move to a soft cotton cloth backed with a cotton ball and soaked with the 5-5-90 mixture. Go over the entire area with medium to light pressure to further smooth the surface.

When it appears to be sufficiently smooth, immediately put some Novus 2 on the surface and spread it around evenly with a finger tip. Go back to the last used cotton cloth swab with some fresh mixture on it. Use that swab to work the Novus around the surface until it begins to turn into a paste (this step is crucial to creating a mirror like final finish).

When the Novus gets pasty, add some more and spread it evenly around the surface using a finger tip. Use a rotating orbital buffer to remove the Novus. Apply a second dab of Novus 2, spread it around with a finger tip and remove it with a rotating orbital buffer. This is the last step in the process.

Wipe the surface off with a clean, dry microfiber cloth. Look at the surface. It should be uniform in color, the original color. If not, go back to step one and redo the complete process concentrating on the darker areas missed the first time around.

For this lighter colored housing, there were a few dark streaks left on the surface (about 5% of the surface was still discolored). It took 5 minutes to go through the process a second time. The first pass took less than 10 minutes so the total color restoration took less than 15 minutes.

The first image below shows how the surface changes when beginning the process. A now removed sticker kept the lower left side from darkening. Chemical sanding for about 3 minutes removed the dark plastic on the upper right area, as marked. This image shows the technique in progress.

The bottom image is a comparison is the same light of the side before and after chemical sanding. You can see the dimly lit tripod and camera in both images, before and after. The after surface had a much smoother, age-mark free finish.


This complete process including information about the high bite cloth used is in a captioned YouTube video (no sound).

          https://youtu.be/bmrcvgjqXmM  (10 minutes long )


Items needed or used in this ABS technique include

  1 )  high bite chemical sanding cloth
  2 )  soft cotton cloth
  3 )  cotton balls
  4 )  Acetone
  5 )  100% denatured alcohol
  6 )  Methyl Ethyl Ketone
  7 )  2000 grit sandpaper
  8 )  Novus 2
  9 )  Rotating orbital buffer with terry cloth cover
10 )  Distilled water in a wash bottle
11 )  Cleaning rag


If anyone would like a few sheets of the high bite cloth, please send me a PM.

( A source for this cloth was stated at the bottom of a prior topic at http://www.classicrotaryphones.com/forum/index.php?topic=20164.0 )

TelePlay

Spent just under 2 hours tonight doing the whole shell. After polishing, a bit of darkened plastic was spotted in 4 places. These will take about a half hour more to remove. Current images below with the side image at an angle showing the quality of the shine this technique produces.

It always amazes me the change that takes place from the first application of Novus being rubbed in the the solvent and then buffing off more Novus added to the pasty Novus from the prior step. Novus really does a nice job on solvent softened plastic.

TelePlay

After a half hour, the missed spots were removed and the housing done. Yeah, it's just beige but it works as an example of what can be done.

Still left to do are the bezel and the handset.

AE_Collector

I guess this is an area to get into trouble...ABS phone housing but are the dial plates usually tenite? Many AE's seem to be...

Terry

TelePlay

Quote from: AE_Collector on April 07, 2018, 11:56:19 AM
I guess this is an area to get into trouble...ABS phone housing but are the dial plates usually tenite? Many AE's seem to be...

Terry

Good question. I did the bezel today and will start a new topic for that video but in a nutshell, this is how it starts and ends.

Flip the bezel over and put a small drop of denatured alcohol on the bezel color plastic and the number (black or white) plastic and let it dry normally.

Look at the two test spots to see if any mark was left (a round circle). If the bezel and/or number plastic shows a circle, it is Tenite or soft plastic. If no mark appears, the plastic is ABS. Denatured alcohol has little if any affect on ABS.

To test for ABS, then put a small drop of acetone on the bezel color plastic and the number (black or white) plastic and let it dry normally (the spot in the image below looks wet but that is what acetone does to dull ABS when drying).

Look at the two test spots. There will be a very clear circle where the acetone dissolved the ABS.

Based on this test, use the appropriate solvents.

In this case, the denatured alcohol on the beige bezel plastic showed a faint circle. As such, the acetone was diluted 25% with denatured alcohol - a 75% acetone, 25% denatured alcohol mix. This mix was chosen to slow down the affect of acetone on the beige plastic which due to the faint circle present in the DA test, which indicated the beige plastic was somewhat susceptible to DA, and as such, probably very susceptible to acetone. The mixture worked well.

The first image below is the plastic test.

The second image is the before and after bezel photos. The bezel was taken to the end as described in the chemical sanding method above, ending with the final solvent and Novus 2 polishing and then Novus 2 with a rotating orbital buffer. This left the bezel too shiny and there were some minor sanding marks on the surface along with a couple of the black dots had a thin layer of beige plastic over them.

As such, all was fixed by going back to 1000 grit wet sandpaper which removed the marks and beige layer over the dots. Since a shiny surface was not desired, 2000 grit wet sandpaper was used right after the 1000 grit to smooth out the surface. When rinsed and dried, the surface was mark free, the black dots cleaned off and the surface was 2000 grit full. To finish it off, a soft cotton patch backed with a cotton ball and dampened (not soaked) with the 5-5-90 mixture was gently rubbed over the surface. While damp, a few drops of Novus 2 were put on the swab and rubbed into the bezel. The final step was to remove the Novus 2 using a clean, dry microfiber cloth.

The final finish was smooth, back to the original color and had a nice satin look, a surface type recently discussed on the forum as more appropriate for a bezel so the numbers would or could be seen better without a shine. Owner preference, I guess. I left this one with a satin surface.

With the bezel done, the handset is next.

poplar1

That is the latest style number plate, developed for 9CA dials. So that style was not produced before about 1974. What year did WE stop making soft plastic number plates? I'm guessing it was way before 1974.

The metal clamping ring that held the number plate on 9C dials tended to disengage from the slots in the dial, making the number plate loose. The 9CA overcame that problem: the finger stop -- no longer attached with a screw -- now had to be removed so that the number plate could be installed by rotating it into the locked position.
Mets-en, c'est pas de l'onguent!

"C'est pas une restauration, c'est une rénovation."--François Martin.

WEBellSystemChristian

Wow, how did I not see this topic sooner?!? :-[

Great job, John! I never really thought it was possible to chemical polish ABS without doing something uncontrolled, expensive, dangerous, or with poor results. It certainly looks like you proved me wrong on that one! ;)

The cotton ball idea is also a great idea! It should also keep the edges of the paper tucked up neatly, away from the surface. The plastic isn't fun to correct once you have a stray edge of paper dip down into the wet surface! >:(
Christian Petterson

"Whether you think you can or think you can't, you're right" -Henry Ford

TelePlay

Did the handset tonight, a somewhat difficult item to hold and chemically sand. While fresh in mind, a few additional helpful hints.

On something like a handset, no need to really soak a swab with the plastic stripping solvent. If the swab is soaked, the excess solvent will run onto a side not being worked and cause an "Oh, no!" to be smoothed out. Best to keep just enough solvent in the swab cotton ball to work one area at a time. The final 10-10-80 will not cause marks if it runs onto another side but should be wiped off right away if a run happens just to be safe.

It takes a bit of time, a minute or two, for the surface to dry so don't touch an area right after it has been chemically sanded, it will leave finger or hand prints.

When working on a handset, do 75% of the handset (so you have one end to hang onto), let it dry, and then do the other end.

When using the 75% acetone and 25% denatured alcohol, some deeply discolored areas did not want to sand off easily. In those instances, I have an open tube of pure acetone which allows me to top dress the swab being used with a bit of 100% acetone and use it immediately on the stubborn discoloration. Then, put more of the 75-25 solution on the swab and go over the stubborn area to smooth out the pure acetone chemical sanding marks.

Same thing with the 10% acetone, 10% methyl ethyl ketone, 80% denatured alcohol. When being used after the chemical sanding to remove sanding marks, if an area is found that does not want to come off, top dress the swab with a bit of the 75-25 mixture, remove the stubborn issue and then add more 10-10-80 to the swab and go over that area right away.

The percentage of solvent mixtures is not set in stone. For ABS, the sanding solvent can vary from 100% acetone to, say, 50%-50% acetone and denatured alcohol. The more alcohol, the less ability of the acetone to cut away the discolored plastic. I found 75-25 worked well this beige phone. Basic rule is if something cuts too fast, dilute it. If a mixture is not doing the job, increase the percentage of cutting solvent.

What to look for between the steps is also learned with practice. Rarely will I find a sandpaper mark but chemical sanding marks are somewhat common if missed in one of the steps. It is easy to go back and do just one spot when discovered and get it caught up to the rest of the handset. And even if the marks are found after the final polishing step, it takes but a few minutes to remove a mark and bring it to a high shine. Removing the discoloration takes the longest time in the entire procedure.

All of the above is learned with experience. Practice on a junk, busted up housing is suggested. It can be brought to a shine and sanded down to start over many times. I know from experience the better one gets at chemical sanding, the fewer "Oh, No!" issues occur. I've been doing this for some time know and right now I would be thrilled to do a complete set of phone plastics with not one "Oh, NO!" showing up. Knowing in advance from experience what causes the issues goes a long way to not letting them happen in the first place.

====================

I use finger cots on my thumb and first two fingers to hold the acetone filled cloth swabs. They are available at drug stores for something like $6 for 30. I get mine from China at under $5 for 300. The salon quality cots are tough enough to not wear through while doing a whole handset. Exam gloves wear through quite fast because all of the pressure is concentrated on each finger tip. There are other, thinner cots available for other uses, the thicker salon cots are best (images below).

====================

Took about 45 minutes to do the handset (hard to hold and a lot of corners). It is back to the original beige. The caps will be done tomorrow. The light in this image was not the best, the left side of the handset and cap is more what it looks like. The beige color that was under the yellow gold looks very nice.

====================

PS: I have not stopped using the "GLOBAL MODERATOR" and "Regular Member" qualifiers on replies I post to other members topics to make sure no one confuses whatever I say as being that of a global moderator about the forum or adding a topic comment as a regular member. When I am posting in my own topics, it is obvious I am posting as a regular member and those headings are not needed. The qualifies are just trying to keep my diminishing number of posts clear to intent for those who aren't quite sure of why I am posting a reply in another members topic.

cihensley@aol.com

Very good John. Your various postings on chemical sanding has added immeasurably to this method of restoration.

Chuck

Dan/Panther

A disclaimer here.
For those of you that are into the plethera of challenges going around, Please take note.

FINGER COTS ARE NOT A SUITABLE SUBSTITUTE FOR THE RECENT INHALE CHALLENGE.

D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

andy1702

I've been using a similar technique to this for a while now. It works really well on ABS. See the video link below.
https://www.youtube.com/watch?v=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

Finished the phone last night. The handset caps were dark but the plastic batch seems to be different, a bit darker beige. All the sides are even colored. The one side of the caps that got more "sun" than the other over time is now the same color as the inside of the cap.

So, in summary, what did I end up doing? I turned a $10 phone into a $12 phone by using it as the object to describe my method to remove discolored ABS plastic using chemical sanding.

It turned out pretty good, about 95% of what it would have normally ended up had I not been doing a lot of the work under a camera. There are some sanding marks in a few places that could now be easily removed by going back to 1000 grit wet sandpaper, final solvent, 2000 grit sandpaper, final solvent, Novus 2 rubbed in with the final solvent and then Novus 2 buffed off. I actually did that to 2 or 3 spots prior to taking the photos and those before and after would not have been picked up by the camera. The touched up spots were either a bit dull or a bit wavy. One thing nice about sanding plastic after the discolored layer is removed is that the sandpaper is much more effective on the original plastic than it is on hard, discolored plastic.

The finger wheel had very minor, normal scratching on the number card window. I used the final solvent mixture on a soft cotton swab to dampen the plastic, rubbed Novus 2 into the plastic with the same swab and then put a bit more Novus 2 on the finger wheel and used by orbital buffer to take it off. The number card window now look like NOS. No sandpaper was needed but deep scratches, if they were there, would have been removed with 1000 grit wet before applying the final solvent mixture with a soft cotton swab.

As I said before, the bits and pieces (any step) of this total procedure can be used to resolve anything that comes up with great success.

If anyone tries my way and wants to comment on how it turned out or if a better step, better way is found, it would be nice if they posted replies in this topic or started their own topic on this board. It doesn't matter. What's important is to share what can be done in detailed steps that can be repeated by other interested in chemical sanding. Starting from this point in time, this method based on previous work by cihensley and WEBellSystemChristian, I am sure it can be improved and hopefully anyone finding a better way will take the time to post their way somewhere on the forum. It's those little and sometimes numerous "Oh, No!" moments that move the process forward.

The phone was tested and works so I now have a highly desirable  ;) $12 beige 554 for my kitchen wall. Here are the after photos.

Pourme

Benny

Panasonic 308/616 Magicjack service

WEBellSystemChristian

Great results!

I think I'm going through denial in believing that was chemically polished! ;) Until now, I always associated "ABS" and "Solvents" with the mental image of irreversible solvent streaks! It looks like we now have the image of a highly polished phone to replace it! 8)
Christian Petterson

"Whether you think you can or think you can't, you're right" -Henry Ford

TelePlay

Quote from: WEBellSystemChristian on April 10, 2018, 08:55:16 PM
Great results!

I think I'm going through denial in believing that was chemically polished! ;) Until now, I always associated "ABS" and "Solvents" with the mental image of irreversible solvent streaks! It looks like we now have the image of a highly polished phone to replace it! 8)

Two different types of streaks can occur, discoloration streaks and chemical sanding streaks I call waves. The discoloration streaks are removed by more chemical sanding. The waves are removed with the 1000 and 2000 grit papers

The sanding solvent concentration is a dual edges sword, too weak and it takes forever to remove the discolored plastic and to strong can lead to waves in the plastic under the discolored plastic. Using the soft cotton swab after all discoloration is gone smoothes out the surface. The sandpaper removes the rest. Since the original plastic is solvent soft, sanding works quickly to smooth the surface. The final solvent mixture smoothes the sandpaper marks.

When wet sanding with 1000, rinsing and wiping the surface makes it clear where minute waves still exist so you know exactly where to sand a bit more. When the waves are gone, the surface is evenly 1000 grit dull. The 2000 grit wet sandpaper smoothes the 1000 grit and gets the surface ready for the final polishing steps.

I can't emphasize enough the drastic change the occurs in the plastic from 2000 dull to highly polished that takes place in using the final solvent on the 2000 grit surface followed by adding Novus 2 and rubbing it in with the final solvent and then more Novus 2 removed with the orbital buffer. If the sanding left a smooth but dull surface, after one buffing the surface will be a mirror.

If after the final buffing, discoloration streaks or waves are seen, just go back to the step where they should have been removed, remove them and work forward to the final polish. Takes a few minutes to touch up an area.

When I put the buffer to the Novus 2 on what was a 2000 grit surface, it stays dull while the Novus 2 is wet or damp but as soon as it is dry buffed off, the high gloss surface magically appears.

Take a junker ABS housing, sand it with 600 grit dry paper and start the chemical sanding procedure there. Actually, dry sanding badly discolored ABS cuts the hard to layer and speeds up the removal of the discoloration, a tip I forgot to mention above. This will show well how the combination of solvents and wet high grit sandpaper with together to restore the surface.


And with the sanding, I've never had to deal with sandpaper grit marks thanks to the solvents. They never show up, no circular sanding marks from prior grits.