WE Plastic Discoloration - different shades of white layer removal

[TelePlay]

Pulled this phone out of storage, bought it a long time ago, and at first glance it looked like a two-tone phone.



The dial was coded -58 (white) but the inside of the housing was not white.



The exterior was white but was quite marked up



I used a weak mixture of acetone and isopropyl alcohol to see it the marks would come off. They did and so did the white paint. This phone was nicely painted at one time but not with Polane. The emblem showed no sighs of paint, Polane usually fills in the lettering a bit.



The cradle ears were similar to black metal 302 housings in that the paint was worn off exposing a yellow plastic below the paint. I moved up to a stronger (75%/25%) mixture of acetone and isopropyl alcohol and found that mixture easily removed the paint leaving a very nice, smooth shiny yellow plastic below it.

I first removed the paint on the side opposite the handset and discovered a light, pastel yellow I had not seen before. I then removed the paint on the handset mouse hole side and discovered a much darker yellow plastic.



The back and the dial front had a shade of yellow between the sides. Before being painted with this soft white paint, this housing must have been placed near a window where the front and handset side were exposed to sunlight, then just the side and finally the side and the back. With the handset side getting a full days sunlight, the front and back only a half days light and the far side just incidental light, that created 3 shades of discolored white plastic, 3 shades of yellow.

This image shows the front side with only 1/3 of the paint removed, the shiny yellow is on the right, the soft white marked up paint on the left. It also shows the paint worn off the cradle ears by the handset.



The housing will be a two step process to remove the discoloration, removing the paint and then the top, thin layer of discolored white plastic. The bezel and handset are much darker yellow than any part of the housing meaning the housing, before it was painted, had turned yellow but the paint protected the housing surface from sunlight freezing the discoloration to that of what it was when painted. The bezel and handset, having no paint, were exposed to light since 1961 and while most likely white when mated to the painted white housing, began to discolor and continued to discolor turning them into a much darker yellow.

What was interesting is that the inside of the housing and the handset were also yellowed indicating that the white plastic itself had chromophores that became degraded on their own, did not need sunlight. The insides discolored more slowly than the exteriors which must have had both self degradation of the chromophores but accelerated by UV rays in the sunlight.

   

[TelePlay]

As a final test before beginning a full color restoration of this phone, I used a 85% acetone 15% isopropyl alcohol mixture on a patch of WypAll 60 high bite cloth backed by a small cotton ball and concentrated on a small circular area on the darkest yellow side, the handset side.

After about 3 patches (the cloth does fill up with removed plastic), I was down to the original white plastic (the white below the cradle is still the paint).

In that the paint is not Polane, it will come off easily with an acetone/isopropyl alcohol mixture on WypAll patches to be follow by a stronger acetone mixture to remove the discolored plastic. From my experimentation so far, it may be possible to restore this entire phone without sanding in that the discoloration itself is softer than expected and can be removed with chemical sanding using something less than pure acetone.

The moral of the story is an oxidizer, bleach or hair developer, would not work at all in that the different sides would require a different exposure time and getting the phone "even" would most likely not be possible. Oxidizers have worked with lighter phones, to some extent, but as I've always advocated, the best way to color restore a phone is to physically remove the thin surface layer of discolored plastic.

Will post after pictures when finished.

[FABphones]

Really interesting thread and great detail - lots for us to learn here. Thanks for taking the time to type this up and for the great photos.

Will follow the thread with interest. This is going to turn into a really smart phone.

 

[TelePlay]

The paint on this phone is unique to me. I've had housings coated with Polane which is a hard surface, glossy impossible to remove paint that does not discolor over time.

This housing had a white paint that did not fill in the lettering on the emblem, it was that thin, but it did cover the housing with a soft coating that marred easily, showed dirt and wore off the edges of the cradle ears.

While removing the remaining paint, I wondered if another solvent would work. Tried 100% lacquer thinner on a cloth and the paint dissolved off into the thinner of the cloth very easily, no rubbing, just wiping.

It was easily removed with a thin, non-polar paint thinner, lacquer thinner. Even lacquer based paints when thoroughly dry do not dissolve this easily with lacquer thinner.

Does anyone know anything about this type of paint that used by WE in the early 1960's to refurb discolored housings?

[TelePlay]

The next step was removal of all paint on the housing. With the paint removed, the approximate discoloration and discoloration areas of this housing can be seen as it was just before being painted white.

The discoloration was the darkest on the handset mouse hole side, lightest on the non-mouse hole side. The front and the back were in between shades of yellow. This is a big indicator that UV radiation from sunlight was the energy that chemically changed the chromophores in the plastic that originally made the plastic look white. White is the reflection of all light that hits the surface. With a change in the surface chromophores, they began to absorb red and blue wavelengths leaving only the yellow wavelengths to be reflected, seen as yellow where the discoloration occurred. All light was not being reflected to make the plastic look white.

What's interesting is that the handset cups provided protection (shielded the plastic behind the cups from UV light). But that protection was less on the dark (mouse hole) side than the other side. With the paint removed, much of the plastic behind the handset cup on the non-mouse hole side



was still white plastic. The mouse hole side had a lot more discoloration in that area (the white spot toward the front was a discoloration removal test using an acetone/isopropyl alcohol, shows the original white plastic).



The front and back had different shades of yellow and more white than yellow near the cradle area.





The front right side edge that rolls off to the non-mouse hole side is white because that was the first discoloration removal test area, two areas annotated in this image.



The only thing that I don't understand is why the inside of the housing has an even yellow shade, no white showing anywhere. There is a lot of white plastic in protected areas of the housing but the inside, having the greatest protection of all from sunlight, is yellowish.

 

[FABphones]

...why the inside of the housing has an even yellow shade, no white showing anywhere...

I wonder if the shell was from a disassembled returned phone, placed upside down in a parts bin awaiting reassembly, yellowing during the interim. In my experience of other telephone factory assembly lines there is a lot of glass to the roof and top area of walls, so a lot of natural daylight fills the workplace.

[TelePlay]

Could be, never thought about that. I guess they might want to shelf them upside down to keep dirt off the surface and avoid scratching if anything landed on it.

I'm not going to restore the inside but I can do a test spot.

[MMikeJBenN27]

Maybe painted by the subscriber after the breakup of the Bell System.

Mike