Crazing - Paint, Coating or Plastic?

[poplar1]

Jim, in what way are they marked"C"?

[TelePlay]

Sorry to resurrect an old post, but it fit this topic perfectly. I have a red 500 that has some significant crazing. From what I can tell, it appears to be a '62 that was refurbished in '73.

podor,

No, great post. I started this topic as a place to document and discuss this noted affect. It's more common than not but it is also not well understood, the cause, that is, in some cases. unbeldi has provided good information but more examples are welcome as they are found.

Jim, in what way are they marked"C"?

I think this is what he means by marked "C" and my red drilled 500 shell does have a "C" and a 75 for 1975, the creation date.

[unbeldi]

The "C" in the mold date dial ?

The letter in those was always either C or P, and were present when the housing was newly made.  These date marks were used starting in January 1960 on all new sets.
We have not found the meaning of either C or P.

[TelePlay]

The "C" in the mold date dial ? The letter in those was always either C or P, and were present when the housing was newly made.  These date marks were used starting in January 1960 on all new sets. We have not found the meaning of either C or P.

Well, I can't help with this other than taking that picture of the mold date dial, what I just assumed he was referring to on the shell. As soon as Jim H logs in he can confirm that was what he was talking about in his prior post or tell me where to look the the mysterious "C" on/in the shell.

[podor]

I'm curious about the C myself.

I happen to have a red 2554 and a green 2500 with plastics from the same year with no crazing at all. I cannot tell any difference between the castings of the handsets. There could be some truth to the recycled plastics. The 2554 and 2500 were new in 73 where as the 500 was a refurbish from 73. Maybe the recycled plastics went into the refurb shops. I am 99% sure it isn't coated or painted.

My OCD has a real problem with the crazing. I'm wondering if I should go a little deeper with the sanding? I would hate to take it too far on a phone that will look pretty sharp once it's polished, even with the blemishes.

[podor]

Here are some after pictures. It is better, but I can still see it. I can't get a good picture with the shine.

[TelePlay]

This is the first "good" photo I've been able to take of my red '75 shell, the area on one side of the cradle. The other side does not show these markings. This is the "worst" area on the phone and it is very hard to see, much less photograph.

The two photos below are the same. The first and smaller is notated with a yellow and 3 blue circles. The blue circles show the crazing that is just starting. The yellow shows the "pitting" that I have seen when working with solvent melted plastic to fix chips and cracks. If this was a sprayed on top coat, this could be solvent evaporation on an area where they sprayed too much top coat. I don't think a "dip" to re-flow the surface would or could result in such pitting.

To end the red crazing mystery posted above, determined today that the housing was both painted AND clear coated. The clear coat being very resistant to straight acetone, the paint no so much.

Still don't know why this "pop out" below occurred unless it was a paint chip flaking off before the clear coat was applied and missed by QC, if any in this process.



So, the cause of the crazing on my Rockford Phone which started this topic is probably the same, clear coated black paint. I would guess that when first applied it looked like NOS and over the years the crazing appeared for several stated reasons.

That clear coat they used is a very hard and tough surface which withstands hard buffing and shines up well, but buffing does not get rid of the craze marks.

[Dan/Panther]

This is a very common occurrence to items clear coated with a Nitrocellulose Lacquer. Very common with guitars, ESPECIALLY those residing in the North East, or South West United States. Those two regions because of the extremes in DRY weather.

Dan

[AL_as_needed]

Plastics are an odd material, made up of a mixture of resins (usually a milky clear) and the actual color additives. Both are pelletized and mixed in a given ratio prior to melting down and sent to the injection molds. It can take A LOT of material and time to get an injection molding line running a particular product correctly as each batch is a bit unique. Items made in the under-run and over-run periods will be off spec as the machines are finely calibrated in the beginning, and then fall out of spec late in the run. (Injection molded plastics are pretty corrosive to the machines that heat and inject the materiel and have a service life depending on the type of plastic molded, PVC being the worst).

Now to crazing, this usually comes up if the plastics base resin material being not properly stabilized chemically. This could be as simple as the chemical purity of the resins was a bit off (too acidic), the temperature and flow rate in the molding is uneven or the mixture density is off spec and causing stress during expansion/contraction with temp changes.

Additionally, If plastics are exposed to say lots of UV or oils, this can accelerate the breakdown of the resin base on a chemical level and make it brittle (fading is a symptom of this breakdown). The only way to "fix" this sort of thing is to sand down the area and even open larger cracks and refill with new resin, not unlike work on a fiberglass boat. However in terms of material strength, its sadly a one way ticket as all plastics, especially new ABS all get brittle with age.

[Jim Stettler]

Looking at early postings I see I never replied about "C"
. It  is a raised "C" in the same size and font  as the "E36" mark in reply 17.  There are articles about recycling plastics and marking them in Bell Labs publications.
JimS.

[TelePlay]

That is very interesting.

I just came up from the dungeon having done some work to explore that housing surface.

I discovered the clear coat over paint by trying to remove a ding in the plastic. As I sanded it out, the red under the ding got darker and realized they must have painted the housing because it had darkened over time. Seems as I removed the paint/coating, I also ended up removing the thin darker plastic so the plastic exposed by sanding is the same color as the paint, the original red. The color right under the paint was very dark, almost maroon.

Took this image to show an interesting problem. The right side of the housing (vlue circle) is the as received red, slightly crazed red plastic. On the left (green circle) is the original plastic exposed using wet 400, 600, 800, 1000 and 2000 grit paper followed by a denatured alcohol rub and taken to the buffer (that white streak from the lower left to the upper right forking off downward is my arm and fingers holding the camera. The area in the middle (yellow circle) is the paint/coating which has been sanded but not completely removed. That area got the same amount of buffer as the left side did. The paint/coating is indeed a tough finish that only sandpaper seems to cut through. I can not be buffed shiny.

Tried Easy Off oven cleaner but nothing happened. Now using CitriStrip which seemed promising on a test area inside the housing.

This is a good housing for me to practice on. The handset and housing were drilled to be a lamp phone and if it doesn't turn out well, I can always paint it before restoring it as a lamp, if the paint turns out well. It's not worth sanding the whole housing so it may get painted.