Cold Case File #34: The Case of the Mysterious Green Goop

I think I finally have an explanation for this, and it only took five years.

When I first read the original thread, I was partial to the external water leak theory, causing the copper to corrode and turn green. But after re-reading all the posts in the original thread, and then adding in godfather's post today, a new theory emerges. This is crazy [big surprise], but please bear with me.

One piece of info popped up several times: The green goo is sticky but flowable, kind of like melted plastic. And kind of like the protective green coating on the boards, when it is first put on and before it sets up. This is clue #1.

Here is clue #2: Years ago, I tossed a handful of plastic fishing worms into the bottom of a plastic tackle box. A week or so later, I opened the box to discover that the worms had appeared to melt right into the box. Closer inspection revealed that the worms hadn't melted, the box had. The area of the box that was in contact with the worms was sticky and flowable. It never hardened back up. Years later, I found out why: Some plastics [in this case the worms] contain "plasticizers" that can migrate into other plastics during prolonged contact. Some plastics don't like some plasticizers, and they will be permanently changed and can even become semi-liquid.

Here's the theory: One or more parts on the board contained plasticizers that, over time, reacted with the coating on the board and altered it, making it "flowable" again. The effect is more or less permanent, and the stuff never actually re-hardens. This may only happen on certain boards with certain components, as you all know there were many different versions of 400 cards. That would explain why it doesn't happen all the time. It probably takes decades to happen, which is why Western Electric was never aware/concerned about it.

So, does anybody buy this, or should I book myself a room on the farm?

Jim
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Cooking up theories in a secure undisclosed location.