Pitted Lacquer Finish

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BaritoneJack
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Pitted Lacquer Finish

Post by BaritoneJack » Sat Jun 09, 2018 7:10 pm

I've just bought a Bach Selmer tenor trombone, which seems in good nick mechanically; as far as appearance goes, it looks like it's got a severe case of measles, where the lacquer has flaked off, and the brass underneath has slightly corroded. (I've not posted an attachment on here before, but I'll try posting a picture showing what I mean).
Photo0004.jpg
Photo0004.jpg (31.2 KiB) Viewed 280 times
I couldn't find my camera, so had to use the one on my mobile, which isn't the best.

I realise that the best route would be to send it along to McQueen's, my local (top-notch) repairer in Manchester, and have them strip, polish and relacquer it or even silver plate - but not having six hundred quid to spare, that's a non-starter.

So is there anything I can do to improve it, but far more importantly, stop it getting any worse? I can't think of anything which would remove the verdigris from the tarnished spots without messing up what's left of the lacquer - and the only other option I can think of is to strip the lacquer off completely, polish the brass and keep it that way. Being ex-RAF, I had a LOT of practise keeping brass clean and shiny - but it would still call for careful handling to avoid a lot of regular hard work.

Any suggestions, shared experiences, or dire warnings would be most appreciated!

Baritone Jack
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ghmerrill
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Re: Pitted Lacquer Finish

Post by ghmerrill » Sat Jun 09, 2018 8:10 pm

There is no need to "polish the brass and keep it that way" unless you require it to be shiny. Raw brass will acquire a patina that many find attractive, and that some feel contributes to a distinctive sound quality. A danger of stripping and re-lacquering (or plating) is -- particularly in the case where you want to eliminate the unsightly dings -- is that this will require buffing, which may (or likely will) affect the thickness and evenness of the brass, and so affect the sound of the instrument.

An alternative would be to strip the lacquer and give it a "scratch coat" (done with steel wool or a scratch pad), and then lacquer it. This would hid the blemishes without the dangers involved in buffing. It can also yield a very attractive appearance if done well.
Gary Merrill
Wessex EEb Bass tuba
Mack Brass Compensating Euph
Amati Oval Euph
1924 Buescher 3-valve Eb tuba
Schiller American Heritage 7B clone bass trombone (DE LB K/K9/110 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)
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BGuttman
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Re: Pitted Lacquer Finish

Post by BGuttman » Sat Jun 09, 2018 8:20 pm

One thing you could try on the "pits" is a corrosion wadding. We have a brand here in the States called Nevr-Dull. You will probably find something similar in an auto parts store in your area. It's a cotton wad with a chemical that dissolves tarnish. You may find it doesn't do too much damage to the lacquer and may let things be acceptable.

FWIW, I saw a similar problem on a Bach 50B3LO where the seller thought it was red rot (it was not). I didn't buy that horn since I don't particularly care for Bach bases, and particularly don't like ones with large bells.
Bruce Guttman
Merrimack Valley Philharmonic Orchestra
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BaritoneJack
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Re: Pitted Lacquer Finish

Post by BaritoneJack » Sat Jun 09, 2018 9:41 pm

ghmerrill wrote:
Sat Jun 09, 2018 8:10 pm
There is no need to "polish the brass and keep it that way" unless you require it to be shiny. Raw brass will acquire a patina that many find attractive, and that some feel contributes to a distinctive sound quality.
Um - the trouble is, all the instruments in the brass band I play with are shiny; if I was to allow it to dull down to a typical unpolished brass patina, it would stick out like a sore thumb when we play in public - if I did that, I think the band would feel that I was showing them up in front of our audiences, and so would I.
A danger of stripping and re-lacquering (or plating) is -- particularly in the case where you want to eliminate the unsightly dings -- is that this will require buffing, which may (or likely will) affect the thickness and evenness of the brass, and so affect the sound of the instrument.
It only has about three very small and shallow dings, and - oddly enough - they don't appear to have done any harm to the lacquer at all! They're the sort which could be removed quite easily with one of those steel ball / super magnet tools without any need for buffing afterwards. But they are so minor that I don't think they're worth worrying about.
An alternative would be to strip the lacquer and give it a "scratch coat" (done with steel wool or a scratch pad), and then lacquer it. This would hid the blemishes without the dangers involved in buffing. It can also yield a very attractive appearance if done well.
I still think I'd rather polish it before re-lacquering if I took that approach; I very much doubt that a fine grade of polish would remove any significant depth of metal - and it would be far less than even the finest grade of wire wool. But if I did re-lacquer it, what sort of lacquer should I use - bearing in mind it would have to be one that could cure properly at room temperature (as I believe that pro-repair shops use lacquers which are baked in ovens after application).

Many thanks for taking the trouble to post such a detailed reply, and my best regards,

Jack
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BaritoneJack
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Re: Pitted Lacquer Finish

Post by BaritoneJack » Sat Jun 09, 2018 10:16 pm

BGuttman wrote:
Sat Jun 09, 2018 8:20 pm
One thing you could try on the "pits" is a corrosion wadding. We have a brand here in the States called Nevr-Dull. You will probably find something similar in an auto parts store in your area. It's a cotton wad with a chemical that dissolves tarnish. You may find it doesn't do too much damage to the lacquer and may let things be acceptable.
I did a search on the net for Nevr-Dull, and found what looks like the same sort of thing marketed in Britain; it used to be called Duraglit (which I used on my cap badges when I was in the RAF), but is now labelled Brasso. They also do a version meant for silver, gold and aluminium called Silvo - which I would guess is even finer. I can buy them in my local supermarket, and they don't cost much, so I'll give them a try and report back on how it goes.
As long as the oxidation hasn't crept under the lacquer, that may well do a good enough job; if it has got under the lacquer, then the lacquer will have to come off altogether.
I had that problem on the rear mudguard (fender?) brackets on the Harley Sportster I owned about 30 years back. The lacquer got a few tiny cracks in it, and the corrosion spread like wildfire underneath it. In the end, I took all the lacquer off with wire wool, polished it with aluminium polish, and - even though I lived within loudhailing distance of the beach, the alloy brackets never corroded, even in winter when the whole town was badly exposed to south-westerly storms!
Thank you for the suggestion, Bruce, and best regards,

Jack
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LeTromboniste
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Re: Pitted Lacquer Finish

Post by LeTromboniste » Sun Jun 10, 2018 7:15 am

Yamaha has a product, simply called "Metal polish". It is very similar to Brasso, but I'm told it's even finer. It doesn't scratch the metal at all - in fact I use it to polish my raw brass inner slide when it's too oxidized.
Maximilien Brisson
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ghmerrill
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Re: Pitted Lacquer Finish

Post by ghmerrill » Sun Jun 10, 2018 8:09 am

BaritoneJack wrote:
Sat Jun 09, 2018 9:41 pm
It only has about three very small and shallow dings, and - oddly enough - they don't appear to have done any harm to the lacquer at all! They're the sort which could be removed quite easily with one of those steel ball / super magnet tools without any need for buffing afterwards. But they are so minor that I don't think they're worth worrying about.
Just a word of caution here ...

Personally, I would not attempt to use the ball/magnet technique in this case -- at least from I can see. That approach works very well in removing dents in large diameter tubing (such as found in tubas and euphoniums). It is NOT the technique of choice for small diameter tubing, and certainly not for removing dents from bells. It is also not particularly good for removing very small dings of certain sorts. You can quickly ruin an instrument by using the ball/magnet de-denting technique in circumstances like these. In fact, I can't imagine using that technique on any trombone, but a professional tech might offer more insight into this. Classic methods would be more effective and much safer.

I base this on what I've read (by repair techs) concerning use of the ball/magnet approach, and on my own experience. I very successfully de-dented my 1924 Buescher tuba using this approach -- except for the myriad dings where it appeared to have been used as a target for a BB gun. I somewhat successfully used the technique to remove a couple of dents from the bottom bow of the Cerveny 781-4R (red brass) tuba I had some years ago. But that was very tricky and scary owing to the softness of the brass. It was clear in both cases that any attempt to use the technique anywhere in the bell section would have been a disaster.

The ball/magnet approach can be marvelously successful. But it's important not to attempt it outside the parameters where this is the case. I wouldn't touch a trombone with a ball and magnet. Just my take on things.
Gary Merrill
Wessex EEb Bass tuba
Mack Brass Compensating Euph
Amati Oval Euph
1924 Buescher 3-valve Eb tuba
Schiller American Heritage 7B clone bass trombone (DE LB K/K9/110 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)
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BaritoneJack
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Re: Pitted Lacquer Finish

Post by BaritoneJack » Sun Jun 10, 2018 8:31 am

My apologies, Gary - I didn't make myself clear; having watched videos of pro repair techies at work, I can see that though the tools of their trade look almost primitively simple, you need a shedload of skill to use them without doing more harm than good. So if I ever decide to get a dent taken out, I'll leave it to the pros.
But, as I said, they are so small and shallow I doubt very much whether they'd make the slightest difference to how it plays.
But I do appreciate you taking the time to warn me of the dangers of rushing in where angels fear to tread - cheers, mate! And best regards,

Jack
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BaritoneJack
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Re: Pitted Lacquer Finish

Post by BaritoneJack » Sun Jun 10, 2018 8:34 am

LeTromboniste wrote:
Sun Jun 10, 2018 7:15 am
Yamaha has a product, simply called "Metal polish". It is very similar to Brasso, but I'm told it's even finer. It doesn't scratch the metal at all - in fact I use it to polish my raw brass inner slide when it's too oxidized.
Le Tromboniste - thank you for that suggestion; judging by the way it's worked for you, that sounds like it would do what I want - and I'd sooner try something that was too gentle rather than risk using something which was just a bit too harsh.
With best regards,
Jack
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