[R-390] FW: stripping paint

[Dan Merz]

Barry,  pretty much parallels my experience.  The cracks in bakelite radios I've dealt with seem resistant to further propagation. By the way,  phenolic is a plastic,  in the thermosetting class. And  bakelite is a trade  name , or was, of Bakelite Corporation. I suspect most 20-40's phenolic for radio panels or cabinets used wood flour for a filler rather than fiber reinforcement.  I believe thermal mistreatment,  e.g. uneven heating and cycling,  and outright mechanical impact or stress,  are the main reason bakelite ends up cracked. For every rule, there's an exception especially for material that might have been poorly manufactured.  I'm impressed that Collins used metal knobs rather than phenolic on the 390's. Is there a past thread that discusses this choice?
Catalin and bakelite are  related chemically,  catalin is cast from liquid source while bakelite is molded from powder source under heat & pressure.   I've not owned a catalin radio, but have seen a lot of beautiful ones. 
  Dan

Sent from my iPad

On Dec 8, 2012, at 2:21 PM, barry williams <ba.williams at charter.net> wrote:

> I don't know about all of that. At least on the 70+ radios that I have now with the majority being Bakelite. Sadly, I don't have any catalin radios.
> 
> This is a post war, 1946 so it is about guaranteed to be Bakelite. I have the Sam's or Rider's info, I forget which, and can look it up.
> 
> I pretty much ignore cracks unless they are visible and then I don't buy the radio anyway unless for parts. But, you do end up discovering them later on the bench from time to time. I leave them alone unless the crack is large enough to threaten the whole case. The radio cases all get the same treatment- a waxing/buffing with the real Liquid Lustre. The shine and slick surface reflection is beautiful and durable. It also is an excellent cleaner, but regular dishwashing liquid mixed liberally (I hate that word) with water is easier. Almost every radio you find will have a coating of bacon grease and/or tobacco smoke. One of my first radios that I tinkered with was a gem of a Stromberg AM that I got for $3. It looked like it had been in a chemical pool or in the ocean. I was bored. Anyway, 24 hours of soaking it dishwashing soak gave it a beautiful, faultless surface. That is pretty much what got me started with these things. The Stromberg is still one of my all time favorites.
> 
> I've never seen the kind of knobs you are talking about either. They pretty much are all hard, pressure baked Bakelite. Durable. I've seen crumbly knobs but it a rare thing for me. I think my Hallicrafters S-38B and an EC-1 (is that right, Les?) has them. Les has one too and offered to give the whole radio to me when I begged for a knob, but his wife liked it too much when he went to box it up. What are the odds of having someone's wife like a radio too much??? C'mon Les! Go get her a nice, modern radio with a few bells and whistles at the Wal-Mall, and send me the %%&*@ thing!  =8^P
> 
> I've just never seen the horror stories you are talking about. Catalin is certainly a different story. Among other things, it becomes brittle over time. I have a heavy hand mirror that was my mothers that is amber catalin. It suffered when formed into radio cases due to handling and heat. You have to be careful with that stuff but it is worth whatever effort it takes.
> 
> 
> the other other Barry
> 
>> There is at least one significant issue when dealing with "Bakelite" or "Dakaware" items.
>> 
>> While indeed Phenol is the resin that binds all, carefully examine the item(s) BEFORE doing anything!
>> 
>> Carefully examine the item(s) for hairline cracks!
>> 
>> If any are found, then I'd suggest coating with a "neutral" sealant.  If these cracks are not sealed, anything and everything will simply soak in and break it apart.
>> 
>> The only "Phenolic" items that do not have this issue is the sheet based that has layers of cloth.
>> 
>> The "knob" items are essentially flour with Phenol as a binding agent.
>> 
>> This being the case, the hairline cracks are a quick path in for any moisture and expansion, leading to significant if not total fracture.
>> 
>> Bob - N0DGN
>> 
> 
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