What causes telephone plastic discoloration?

[Adam]

Hello, everybody!

We've discussed telephone plastic color fading/darkening/aging a lot here and how to restore it, etc.

But, do we know exactly what causes it?  I always assumed it was caused by direct sunlight, but does inside incandescent light cause it too?  If so, how long does the process take?  Days?  Weeks?  Years?

I have lots of phones from the 60's and 70's that I rotate through use in my place.  I currently have installed on my desk in my office a beige Western Electric 4A speakerphone attached to a beige 6041 key.  But it sits right under where my 60w incandescent light is for that desk, less than 2 feet away.  (No other arrangement is convenient.)  Am I fading my beige speakerphone and key by having it placed there?

If incandescents do it, how about modern LED light bulb replacements?  Better?  Worse?

-Adam
www.losangelestelephone.com
www.manufacturediscontinued.com

[HarrySmith]

Hi Adam, there was a discussion fairly recently about the different lighting and their affects on plastic phones. I don't recall when or where and could not pull it up. It's here somewhere!

[Jim Stettler]

I used to search for conservation articles. There are some good one regarding light degradation. The main problem is UV. If you use fluorescent use all spectrum or UV sleeves on the lamps. The last I read was LED lighting is much better and the light color does have a long term effect. It is best to use the same color light as the object. red light form am red phone etc.
I plan on upgrading to my lights to 2'x4' drop in LED fixtures. These look like the 2'x4' drop in fluorescent and have LED light strips. Then cost is a little over $100 per fixture.
JMO,
Jim S.

[Adam]

Harry: I tried!

All: So, what about the new-fangled LED light bulbs?  I'm thinking about changing over to them in my place. Better than incandescent?

And, how long does it take to do damage?  Does it need to be over a long period, or are we "aging" our phones just by taking them out of the closet and using them occasionally?

[Jim Stettler]

Here is a study on museum lighting.
http://www.getty.edu/conservation/our_projects/science/lighting/

[unbeldi]

Hello, everybody!

We've discussed telephone plastic color fading/darkening/aging a lot here and how to restore it, etc.

But, do we know exactly what causes it?  I always assumed it was caused by direct sunlight, but does inside incandescent light cause it too?  If so, how long does the process take?  Days?  Weeks?  Years?

When you pose the question so generally, I would say, it is dangerous to draw conclusions, as it is always specific to each material and the condition of storage. In general the external factors are
- presence of oxygen and humidity and pollutants
- light exposure
- temperature
- time

In ca. 1990 or 91, I bought the first all-digital consumer answering machine, AT&T 1337, in almost white color and used it for years without any noticeable discoloration. After a move about seven years ago, it ended up being stored in a cardboard box a dark basement with a lot of other old electronics. About two or three years ago, I rediscovered it, and found that it was rust brown with lighter patches where something had touch it or something was lying on it.  When sliding the configuration switches, also plastic, one can see areas that are still much lighter.  Clearly, the discoloration is caused by exposure, but it is obvious that light is not what caused this.  The basement was mostly dark!

Now some chemistry:  Plastics are never pure polymers. They contain a variety of substances as fillers to provide specific material properties, such as hardness, softness, elasticity, strength, electrical properties, color, etc.  To combat the spread of fire when occurring, plastics have long been mixed with agents to reduce or prevent the material from fueling fires. For many years many or most of these fire-retardant additives contained some form of organic bromine compounds. Bromine has the chemical property of stopping free-radical reactions by easily 'absorbing' an electron to neutralize radicals.  But because of this, organo-bromine compounds also easily decompose and set free elemental bromine.  This decomposition can be caused by light or temperature, and happens essentially always, albeit very slowly.  So, time is a factor as well.

Elemental bromine is a very intense dark red-brown liquid at room temperature. As a gas it is lighter brown. When bromine is set free in plastics it causes the yellowing and browning even if present in extremely minute amounts. Free bromine, in pure elemental form, does not exist in nature, because it is very reactive, but in the plastic it is stabilized for some time.  Its high reactivity is the reason that it can be bleached fairly easily with treatments such as the Retro-Bright procedure, or even simply with any household bleach, as is well known among telephone collectors here.

Other than fire-retardants, other organic compounds also decompose into yellowish or other non-clear compounds, so this is always an issue with organics. Early light plastics were chemically unstable and turned yellow or brown for a variety of reasons.

Finally, I want to point out once again and ask to use proper language when referring to these issues.
Fading is the wrong word for this. Fading is the opposite of discoloration. Many times have I read posts, here and elsewhere, when it just was not clear without pictures what was actually meant. Was the material faded from excessive exposure or bleaching, or was it discolored?

I wrote about here before:  http://www.classicrotaryphones.com/forum/index.php?topic=12739.msg133855#msg133855

So, the removal of color or discoloration is fading.  A faded object becomes white or colorless.

[Adam]

[Thread's topic duly corrected.  Thanks.]