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Removing Sun-Discolored Layers With a Bench Buffer

Started by jmagda, September 20, 2018, 02:14:58 PM

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jmagda

I have a 1985 aqua (supposedly) Princess Phone. Right now it's sherbet-green in places, but I know it's really aqua blue under there somewhere. I have a 6-inch wheel, 1/2 hp 3450 rpm bench buffer/polisher. I also have a speed controller where I can adjust the speed of the buffer. My question is: what colors of stick buffing compound to use to remove that discolored layer from the phone? Don't know how accurate it is, but I found the following stick-compound chart:

Brown - 800 grit (aggressive)
Grey - 1200 grit (medium)
White - 1500 grit (medium)
Green - 1800 grit (fine)
Red - 2000 grit (ultra-fine)

Do I just go by the sandpaper grit equivalents, working my way up to "Red" and then finish with Novus products?

LarryInMichigan

I would give it a soaking in a solution of chlorine bleach and water in the warm sunlight for a few hours first.  That should help remove the discoloration.

Larry

HarrySmith

#2
The easier & faster way to go would be to use the acetone "sanding" procedure. Our member TelePlay posted a detailed topic on it and got amazing results quickly with a lot less effort. Check out his topic.

     http://www.classicrotaryphones.com/forum/index.php?topic=20168.msg212587#msg212587

Harry Smith
ATCA 4434
TCI

"There is no try,
there is only
do or do not"

FABphones

Quote from: HarrySmith on September 20, 2018, 04:11:14 PM
The easier & faster way to go would be to use the acetone "sanding" procedure. Our member TelePlay posted a detailed topic on it and got amazing results quickly with a lot less effort. Check out his topic.

I agree. It's the method I use and I have always been very pleased with how nicely the original colour is revived.
A collector of  'Monochrome Phones with Sepia Tones'   ...and a Duck!
***********
Vintage Phones - 10% man made, 90% Tribble
*************

jmagda

I've already done the "Salon Care 40 Volume Creme" method that I read about in this forum, applying with a brush, swirling it around with a soft toothbrush every 30 minutes for 4 hours in the sun in a sealed clear container. It left it blotchy all over with white swirly marks everywhere.  This is why I am now removing a layer with a buffer.

Ktownphoneco

Irregardless of which method you choose, i would strongly recommend avoiding a buffing wheel turning at 3450 RPM in relation to anything plastic.    I sand, then polish plastic with a flannel buffing wheel on a bench mounted buffer turning at 1770 RPM.     For the beginner, even 1770 RPM is fast.   A buffing wheel turning at 3450 RPM against plastic is creating a large amount of heat through friction and in very short order, which can do serious damage to anything made from that material.    Bakelite can stand that sort of speed, but not plastic.

Jeff Lamb
 

HarrySmith

Quote from: jmagda on September 20, 2018, 04:52:03 PM
I've already done the "Salon Care 40 Volume Creme" method that I read about in this forum, applying with a brush, swirling it around with a soft toothbrush every 30 minutes for 4 hours in the sun in a sealed clear container. It left it blotchy all over with white swirly marks everywhere.  This is why I am now removing a layer with a buffer.

Yes, I had the same problem with a light blue phone I tried the peroxide on. I did figure it out eventually, the blotching was due to uneven application of the peroxide & uneven exposure to the UV light. I was able to get that phone done properly eventually. The acetone is much faster & easier. Here is John's topic:

http://www.classicrotaryphones.com/forum/index.php?topic=20168.0
Harry Smith
ATCA 4434
TCI

"There is no try,
there is only
do or do not"

SUnset2

As was said before, don't buff plastic at more than 1800 RPM.  I've had success polishing phones with unsewn buffing wheels, so you can't press too hard.  I got the wheels at TAP Plastics, along with buffing compound for plastic, though I suspect there is a generic equivalent.

jmagda

I know about not using a buffer on plastics at high speeds; that's why I originally stated, "I also have a speed controller where I can adjust the speed of the buffer."

All I'm trying to find out is is the grit-to-stick color correlation I posted accurate?

.....

You can use this for the final buff.

ACE Hardware carries it. The ACE ad is an older one from my files.

TelePlay

#10
     Regular Member Post

From practical experience, I can say with 100% certainty that it is impossible to remove all of the discolored plastic on a Princess phone using a buffer.

1) many places on a phone housing can not be reached with a buffing wheel, even a smaller 6" wheel

2) the depth of discolored plastic is beyond the reach of removal by buffing, buffers are a device to shine a surface and to some extent, remove minor scratches and dings. Buffing is not designed to abrade away a thick layer of discoloration

3) the many sharp edges of a Princess will result in multiple instant plastic "burns" that will require sanding to remove them once melted. 90 degree edges heat up 10 to 20 times faster than a flat surface on which a buffing wheel, at any speed, must be kept in motion to keep from heating up the plastic past its softening/melting point, a bit more than 200 degrees F. Just touching a 90 degree edge for a split second with a spinning wheel will result in melted plastic with cloth from the wheel stuck in the melted, darkened yellowish plastic.


There is only one easy and safe, but time consuming way, to remove the discolored layer and that is wet sanding with multiple grit sand papers. A fast way to remove the discolored plastic layer, for the not so faint of heart hobbyist, is chemical sanding which will require a bit of final sanding, with a sanding block, to smooth the chemically sanded surfaces prior to final polishing with Novus 2 or a similar polish. It is a messy process but it reduces the color restoration time by hours compared with paper sanding only.

Discoloration goes into the plastic way to deep to even consider buffing to remove it, in my opinion and experience.

PBC (plastic buffing compound - blue) on a slow moving string or flannel buffing wheel carefully moved over the plastic surface with minimal pressure to prevent heat buildup will buff the plastic to a shine but again, one small movement in the wrong direction can catch a sharp edge with the wheel instantly heating the plastic above its melting point leaving a dark, and possibly gouged, edge with cloth from the wheel stuck in the plastic.

PBC with a soft wheel can work well on most of the surface area of a 500 or similar housing. It will not or can not be physically used in sharp corners or recesses. Even buffing around the 500 cradle ears can be a challenge. kleenax has shown buffing can be used to restore dinged 500 housings but his examples have never shown how buffing works around the cradle area of a 500 or if it can be used to remove a thick layer of discolored plastic.

I've done more damage with a buffing wheel to plastic parts than I care to admit including handsets and handset caps by not moving the wheel fast enough over different areas,using too much pressure on the surface of the plastic to keep it from over heating or catching an edge. There is always the dreaded "oh no" present of catching an edge adjacent to the area being worked on resulting in dark, burned plastic with cloth from the wheel stuck in the plastic (back to sanding what was once a nearly finished plastic part).

It only takes a split second to ruin something that has been worked on hours when using a buffer.

All of this is just my opinion but it is based on personal experience of using a buffer for over a year before giving up on it for use with plastic, and I never tried to use it to remove discoloration, only scratches and small dings.

My advice here is to get a junk phone housing of any color and condition and practice on it with a buffer before starting to work on the blue Princess. It won't take long to discover how one instance of loosing a grip on the item or catching an edge or not moving it fast enough over the surface will result in burned plastic.

As for compounds, I used white, red and finally PBC. Keep in mind that the more "coarse" compounds cut more aggressively but in doing so also create a lot more heat. And, the compound itself can be set into the plastic if the plastic reaches it's softening/melting point leading to another form of discoloration. Buffing is great for putting a final shine on flat plastic area if the right wheel, compound and speed is used. Buffing is not meant or designed for removing discolored plastic and will not work for plastic items with recesses.

The following chart from Eastwood, a major supplier of buffing items, shows PBC as the only compound recommended for plastic with rough and final buffing be by way of a different wheel both at 1800 rpm.

If anyone has a way to do this, disagrees with me, please post a reply saying how to do it. I'd be interested in knowing how its done.
Yesterday eats you up, it eats everyone up . . .

Dan/Panther

#11
DON'T buff it. That is my advice.
John very clearly explained WHY not to buff a plastic phone.
I was refinishing a guitar a few years back, it was really my first attempt. All tutorials had shown buffing the finish to make it shine. Well I buffed the guitar, and the first time I touched the body, the finish came off, right down to the wood.
Buffing may be OK for metal or hardened paint on a car body, but unhardened paint, and plastics can not take the heat. DON'T BUFF IT.

D/P

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