Should I sand "bumps" on soft plastic caused by cord contact??

[RotarDad]

This is my second post after studying this forum for about a year - thanks for all the great info!!   My question relates to some raised areas on a soft plastic shell caused by prolonged cord contact. In the pictures, you can see bumps on on the side of shell caused by the coiled cord and some small raised lines above the dial on top which I believe was caused by the line cord being wrapped over the top of the phone.

My concern is that the plastic has expanded - will it look OK if I sand it?  How should I proceed?  This phone is a very nice Mahogany Brown so I am thinking carefully.....  Thanks!  Paul

[Phonesrfun]

My own preference would be to leave it as is.  Other than the bumps, the shine is great on that phone.  Once you take the sandpaper to it, you will never get it to shine the same unless you have the skills and patience that only a few around here have.  Definitely not me!

Besides, like the patina in old wood antiques, these marks of age give these antiques character.

My two cents.

[Jim Stettler]

I would leave it as well.
That is a very nice phone as it sits. It shows well and it is a tough color to find.
Leave it be.
JMO,
JIm

[RotarDad]

Thanks for the feedback.  I spent quite a bit of time with the Novus 2 and the plastic did really turn out nice except for those marks.  I've read through Dennis Markham's M. Brown restoration and deep scratch removal - he does have both talent and nerves of steel....

I've never seen this issue mentioned, except when the cords leave marks in the paint on the bottom -I guess the flexible plastic reacts with surrounding materials.

[Jester]

As Bill & Jim mentioned above, it is a matter of personal preference.  I prefer a smooth surface to go along with that glossy shine, so I sand down areas that have those cord "warts".  Any of those areas can be made smooth again.  Keep in mind, though , that using any abrasive on soft plastic will require some patience & careful polishing to remove the resulting scratches & sanding marks.  It can be done, though.

[baldopeacock]

one cautionary step - don't try to use your hand or fingertips to sand those bumps.   Use a block.   Your fingertips would have the opposite effect -- they'd leave a groove.

[Dennis Markham]

RotorDad, this 554 is one that I worked on recently.  I don't know if the photos will accurately show what I refer to as "blisters" in the plastic from the handset cord.  On this particular phone the blisters ran across the front, diagonally.  You won't be able to sand just the blisters themselves, but the plastic in the general area.   If I were doing your Mahogany phone I would plan on doing that entire left side.  At least from the front edge and about 3/4 of the way toward the back.  The sanded area kind of grows.  Because there is no straight edge to begin and end the sanding, it ends up getting longer/wider as you go.  

In my photo of the Red 554, you can see the sandpaper marks left by the first process.  I started here with 400 grit wet sandpaper.  I make sure to make all the improvements with the initial step.  If after a lot of sanding on any particular object, the repair that needs to be made isn't happening with the grit selected, I will drop down to the next number.  Meaning had the 400 grit not worked on these blisters, I would have gone down to 320.  Only go as rough as you need to.  I don't remember why I didn't start with 800.  Perhaps I did and it wasn't doing the job.  I like to start as high as possible.

Without making a complete dissertation here on the procedure I use, I'll try and keep it short by saying I alternate the direction of the sanding as I progress through the different grades of sandpaper.  I use automotive wet sand paper through 2,000 grit and then switch to Micro-Mesh sheets, up to and including 12,000 grit.  For most projects that is completely sanding the area that you desire to be improved about 8 to 10 times or more.  Figure these grits, 400, 800, 1000, 1500, 2000, 2400, 3200, 3600, 4000, 6000, 8,000 and 12000.  It is tedious work and can be frustrating.  It can also be rewarding when you are finished.  It takes some practice.   It may require doing the same grit two or three times before you have it right.

Once you begin, there's no turning back.  Sanding to remove discoloration is another story.  Usually one has to start with the course grit to get deep enough to remove discoloration.  To improve imperfections caused by blistering (such as yours) or deep scratches, only go as low as you need to.

Another thing to keep in mind.  As you press against the plastic with pressure you increase the risk of creating a crack.  I do it very carefully.  I like to sand under warm running water, just a trickle is good to rinse away the plastic.  But warm water, on a cold housing can cause a crack.  I recently had two housings crack in the same week.  One was a Princess housing which is thin and brittle to begin with. I was only washing that one and it cracked.  The other was a soft plastic 500 housing that cracked while I was sanding the side of it.  I hate when that happens.

[RotarDad]

That is great feedback - thanks guys!  Dennis, I really appreciate all the detail including the grit information.  A couple questions:

1) What kind of block do you use to keep the paper flat against the surface?

2) Where do you buy your sandpaper - is this hardware store stuff or automotive painting supply?

After looking at this, I would really like to remove those blisters.  However, I think I'll have to try this procedure on a black shell or two first to be sure I can get the quality results you are getting!  I've got a shop-worn '61 which someone modularized the line cord on - a good starting point.  Paul

[Dennis Markham]

Paul, I buy automotive sandpaper at the local Auto Parts store.  Just about all of them carry the west sand paper in their autobody repair sections.

When I use a "block" I use a small black piece of spongy rubber that comes with the Micro Mesh.  But to be honest with you I only use that when I have to get the paper on a 90 degree bend for the corners.  I often just use an open palm, being careful not to dig deeper with one finger more than the other.

I find ABS plastic different than Tenite (soft plastic).  In my opinion it is easier to sand hard plastic.  The soft plastic reminds me of sanding soft wax.....it seems to leave sanding marks easier than the harder, ABS plastic.