39 Buick plastic and likely other years as well

[buick looks fine for 39]

The material used in 1939 for knobs and and other parts was not plastic. As I understand it it was a cellulose based material similar in composition to movie film and film negatives prior to WWII. 

As 39 plastic deteriorates there is an acetic acid smell. I think 40-41 plastic is a different composition because as it deteriorates it smells like puke. The main culprits in causing plastic deterioration are elevated humidity and temperature.

I've had good luck bringing back 39 plastic if it hasn't deteriorated too much. On discolored knobs I've used steel wool and once they're cleaned up I switch to successively finer rubbing compound. I've been able to get many plastic pieces looking like new. Also I've had success with warped plastic, like horn button rings and large series handle inserts, using hot water. The plastic becomes more pliable in hot water that is barely tolerable to skin. It can be very carefully bent back to it's original shape after it sits in hot water for a few minutes. Once pulled out of the water it willl turn white. The white film can be removed with steel wool and polished with rubbing compound.

It appears plastic window crank knobs are cast on to a splined shaft and then the shaft with the knob is riveted on to the window crank. I'd like to hear from anybody who has successfully reattached window knob shafts to window cranks.

I've learned these tricks through years of trial and error, but it dosen't mean I know everything about it. Please first experiment on pieces you can afford to lose and be curious.

 

                                                                                                         Thanks

                                                                                                              Leif

[Jolly_John]

A great and helpful sharing of knowledge, Leif. There's so much "good stuff" from the people here on the forums, isn't there? Happy New Year to you. John

Edited January 6, 2023 by Jolly_John (see edit history)

[markewebb '39 Buick Team]

Great info, thank you.  I hope you don't mind; I shared your information with the 39 Facebook group.  

[buick looks fine for 39]

Please do that for me. I don't use facebook