Cutting oil 1960s chassis practice

[centervolume]

Hello - looking for the best forum to post this weird historical question that has to do with chassis cutting and folding practice used for tube amplifiers in the middle 20th century.

I have run into a handful of untouched “museum quality” 1950s-70s Fender amps and find these tend to have a residual powder on the chassis. (fine white powder that yellows with age). Fender chassis would have been mass produced so a larger operation.

It is my understanding that cutting oil is used in chassis manufacture to reduce heat, increase efficiency etc. So my question is about this powder and industry practice back then. Would this have been a commonly applied agent to help soak up residual cutting oil ? If so, is there a specific type of powered like talcum powder that would have been used or whatever gets the job done ?

 

[GregSY]

You're really making a stretch, IMO. No one with an oily chassis would use a dry element to soak up cutting oil.....they'd simply wash it off with solvent...especially back in the 50's-70's when people still had brains.

I can't imagine an amp chassis would be much more than thing sheet steel (?) but regardless...I doubt a lot of cutting oil would be used anyway.

 

[centervolume]

You're really making a stretch, IMO. No one with an oily chassis would use a dry element to soak up cutting oil.....they'd simply wash it off with solvent...especially back in the 50's-70's when people still had brains.

I can't imagine an amp chassis would be much more than thing sheet steel (?) but regardless...I doubt a lot of cutting oil would be used anyway.

Ok so that brings me back to what this white powder that yellows with age might be. I was all to happy to disregard it until was on multiple examples. The fact that all those examples were in like new condition got me thinking the powder was part of the manufacture process.

 

[Joe Gwinn]

Could well have been cadmium plated for rust prevention. No, cadmium metal is not all that dangerous, despite all tye present-day safety shrieking.

 

[Bill D]

Aluminum dust?

 

[13engines]

I seriously doubt they left the factory looking like that. I mean who would think that's okay to send out to customers? Must be something from the environments they've been in all theses years. Or some bizarre corrosion something-something.

 

[GregSY]

I agree, that looks like the plating getting chalky over time....some sort of oxidation.

 

[plastikdreams]

I mean...it's a Longshot right. But really, it could be some old Coke dust.

 

[Joe Gwinn]

Aluminum dust?

Good point. OP - is the chassis magnetic?

 

[centervolume]

Good point. OP - is the chassis magnetic?

Yes it is magnetic. Fender used sheet metal (steel)

apparently other manufacturers like Marshall did use aluminum.

 

[technocrat]

Three guesses:
1. Lacquer sprayed with something like shellac or another organic coating which is breaking down now.
2. Oxidised plating, it looks like tin rather than zinc. Try a drop of hydrochloric acid somewhere unobstrusive. It will fizz on zinc
3. Rosin deposits from the soldering line

 

[john.k]

May also be the residue of a domestic cleaning product ,or a furniture spray ..."Mr Sheen"

 

[centervolume]

Three guesses:
1. Lacquer sprayed with something like shellac or another organic coating which is breaking down now.
2. Oxidised plating, it looks like tin rather than zinc. Try a drop of hydrochloric acid somewhere unobstrusive. It will fizz on zinc
3. Rosin deposits from the soldering line

That’s interesting. I understand laquer was applied in some of the tweed cabinets but those were out of production by 61… I do think the chassis were plated so that may be what’s happening. I think I have some muratic acid on hand will try and see

 

[magneticanomaly]

Old radio chassises I have seen look zinc or cad plated. So I would expect the powder to be a corrosio
n product...oxide or carbonate perhaps.

 

[john.k]

Do not use anything with chloride ion near steel.......uncontrollable rust will result.

 

[EPAIII]

Yes, working in electronics I have seen many steel chassis look like that. I don't know the exact chemistry, but it is the plating that has oxidized. They were clean as a whistle when they left the factory.

As for the manufacturing processes, those chassis were cut, punched, and bent to shape. Lubricants of one kind or another may have been used, depending on the needs of the individual steps, but they would have been washed off with solvent or just plain soap and water before any parts were mounted on them. Just good, old fashioned, sheet metal work there.

If you want to restore them, I would use a fine grade of Scotch Brite pads and some 91% alcohol to wash them off afterwards. But then, I don't know if that would preserve the "museum quality". Perhaps they are worth more in their present condition. Or just wipe them down with the 91% alcohol.

I agree, that looks like the plating getting chalky over time....some sort of oxidation.

 

[trevj]

Yes, working in electronics I have seen many steel chassis look like that. I don't know the exact chemistry, but it is the plating that has oxidized. They were clean as a whistle when they left the factory.

As for the manufacturing processes, those chassis were cut, punched, and bent to shape. Lubricants of one kind or another may have been used, depending on the needs of the individual steps, but they would have been washed off with solvent or just plain soap and water before any parts were mounted on them. Just good, old fashioned, sheet metal work there.

If you want to restore them, I would use a fine grade of Scotch Brite pads and some 91% alcohol to wash them off afterwards. But then, I don't know if that would preserve the "museum quality". Perhaps they are worth more in their present condition. Or just wipe them down with the 91% alcohol.

While the above seems about the most correct answer, the most profitable is probably the Coke Dust idea! Pick a Band! Who'd believe it wasn't true?

In all seriousness, though, go with the idea that they would have washed the parts off, if they had needed any crap added during processing. Even back then, the guys further down the line, would have got cranky about anything on the parts they were handling!

My nickel bet is on a flash coat of plating at some point in the manufacturing process, that is (was) only affected after all these years! And maybe only under specific conditions (storage, use, coke content , etc,)

 

[Philabuster]

Ok so that brings me back to what this white powder that yellows with age might be. I was all to happy to disregard it until was on multiple examples. The fact that all those examples were in like new condition got me thinking the powder was part of the manufacture process. View attachment 393511View attachment 393511

Ever had a parrot as a pet? Our parrot creates white powder dust like that. Our computers are in the same room as the parrot and we have to constantly blow that white dust out of the computers.

Not sure that is the source of the dust, just one possible answer if the Amps were in the same room as a parrot for some time.

How do you control feather dander?

One of our Twitter followers recently asked if we manage dander by bathing the birds a lot. The root of the question refers to the copious volume of dander that parrots (especially cockatoos) produ…

garudaaviary.org

 

[jim rozen]

This is not residual lube from manufacture. It's a cadmium oxide of some type and it's best left alone or sealed. Don't mechanically abrade it unless you know what you are doing. The vintage radio folks know about this, investigate:

Antique Radio Forums • Index page

It''s not plutonium tri-arsenide but yo don't want to inahle or ingest or leave any products from distubing to harm others.

edit: after seeing the photos (long story, did not show up first time) the residue looks too white to be cad, possibly zinc plated steel, so ZnO possibly.

 

[centervolume]

Yes I also found somewhat alarming discussions about use of cadmium as a “sacrificial” coating or plating that would oxidize leaving the steel preserved beneath

Cadmium plated chassis

I’d like to figure out if it is zinc or cadmium oxide (or possibly other substance). I’ve seen it a few other times on vintage amp chassis but in those examples the stuff was yellowing (with age presumably). This chassis had spent most of its life prob since late 70s under the dust cover which may have slowed aging/flow of oxygen.

If this is too white a color for cadmium oxide, what color would have been expected in that case?