[Hallicrafters] S-120 receiver - celloluse nitrate lacquer?

[rbethman]

The old cellulose acetate was the base layer of old film.  It dates back 
to pre 1930's.

The only nitrate on the old film was what was left of the silver nitrate 
that was applied to capture the image.

There are many films of that nature that are very carefully stored, and 
are stored is small numbers in chambers.

I do have an S-120.  Most likely the "goop" under the knobs is the brass 
that will seemingly appear from no place whatsoever.  Every instance 
where I find this happening is where the brass is in contact with leather.

I have this happen to a number of older knives.  It isn't hazardous, but 
simply a royal PIA to end up having to clean.

I don't know what mechanism is the cause.

However, I have NO such happening to my S-120.

Nitrate dope is still in use for aircraft doping of cloth covered 
aircraft.  It causes that fabric to shrink taught.  It is the initial coat.

Bob - N0DGN

On 3/25/2013 2:39 AM, Rich Russo wrote:
> If you are talking about nitrocellulose lacquer, it's not the same as old movie film. Older pianos were shot with nitrocellulose lacquers as well as antique cars and Rolls Royce's up until the 70's. It is still available from Abe Hirschfeld in Newark Nj if they are still around. You maybe able to find them on the web and also in Hemmings auto news. It was a popular paint but was only flammable when it was sprayed and curing. The film on the other hand was flammable all if the time. If it was the same substance used in film, the reason would be that it's thin, a bulb behind it would heat it or burn it, and it was on both sides and it was thin. Remember the fire triangle. Heat, ignition and oxygen. All of those are present with a film reel in use. When used in paint on radios the metal would have to get hot enough for it to outgas and it would not be as much of an issue as in being used in or on film. The case would never get hot enough, the metal would absorb the heat. There i
>   sn't enough temperature present for this to be an issue. I hope this helps. Richy N2ZD
>
> Sent from my iPhone
>
> On Mar 24, 2013, at 11:21 PM, "Richard Knoppow" <1oldlens1 at ix.netcom.com> wrote:
>
>> ----- Original Message ----- From: "Peter VK6PM" <peter_may at optusnet.com.au>
>> To: <hallicrafters at mailman.qth.net>
>> Sent: Sunday, March 24, 2013 7:22 PM
>> Subject: [Hallicrafters] S-120 receiver - celloluse nitrate lacquer?
>>
>>
>>>
>>> I've been discussing off-group whether the clear lacquer used on the
>>> front panel of the S-120 might be celloluse nitrate lacquer.
>>>
>>> You might recall that nitrate is unstable, early movie films pretty
>>> well self destructed before the introduction of "safety film".
>>>
>>> I think that is what's happened to the S-120. The lacquer has "gone
>>> off". The metal underneath looks OK.
>>>
>>> The problem may be present on other S-120s. I wonder if other people
>>> have discovered similar front panel damage?
>>>
>>> Can people also check under the plastic knobs of their S-120s and
>>> look for anything strange, blue and gooey?
>>>
>>> I'm not sure, but this might be caused by off-gassing of the nitrate.
>>>
>>>
>>> Maybe we have discovered a new challenge to keeping these sets
>>> presentable.
>>>
>>> Does anyone have insight as to what clear lacquers were used on these
>>> later Hallicrafters sets?
>>>
>>> Regards
>>>
>>> Peter VK6PM
>>         I don't think this is caused by cellulose nitrate lacquer but use your nose and see if there is an odor of camphor.  That _sometimes_ but not always accompanies the decomposition of nitrate.  Clear cellulose lacquer may also be made from various types of acetate which might cause a gooy residue.  Decomposing cellulose acetate is often accompanied by the odor of acetic acid or vinegar.  Although a clear lacquer of this sort might have been used I am doubtful.
>>
>>
>> --
>> Richard Knoppow
>> Los Angeles
>> WB6KBL
>> dickburk at ix.netcom.com
>>