Pitted Lacquer Finish

[BaritoneJack]

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

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

[ghmerrill]

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.

[BGuttman]

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.

[BaritoneJack]

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

[BaritoneJack]

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

[LeTromboniste]

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.

[ghmerrill]

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.

[BaritoneJack]

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

[BaritoneJack]

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

[BaritoneJack]

UPDATE
I've tried using various grades of metal polish - none of which had the slightest effect, not even Brasso, which is the toughest one I have. On closer investigation, it turns out that the problem is the same as I had on my Harley; the corrosion (which probably started from minute nicks and pinholes) has spread sideways underneath the lacquer - so the only way of reaching it to buff it out is to strip the lacquer off completely. Leaving it alone is really not an option, as in one of the larger spots, it's definitely starting to penetrate the surface of the metal, rather than just being superficial oxidation.
I tried using surgical spirit, to see if that would soften the lacquer, but it didn't make any difference. Green pot scourers matted off the surface finish of the lacquer, but would take forever to strip it right off, so my next step is to try paint stripper.
I saw this being used by a pro repairer on YouTube, and the advantage would be that it wouldn't have any effect of the bulk of the brass which is still shiny, so I'd only have to buff up the spots where it's corroded. If, on the other hand, I use even the finest grade of steel wool, it will inevitably leave a satiny kind of finish all over, which would take a lot of work to polish up - even if I get a buffing wheel on my electric drill, and clamp it into my Workmate.
So I'll try the paint stripper, and let you know how it goes.
If what I've found is anything to go by, I'd caution anyone with one of these trombones; if you don't have this sort of corrosion so far, get Bach's cleaning cloth and follow their instructions to the letter. If you do have this sort of corrosion already, don't leave it - it will spread, and eat deeper into the metal until it goes into holes.

Jack

[BGuttman]

Be careful with the paint stripper. The best ones use a chemical called Methylene Chloride which is carcinogenic and if used without adequate ventilation can replace all the air and suffocate you. It's REALLY dangerous stuff.

Bach lacquer can sometimes be stripped with VERY hot water (70C+). I don't think Bach has gone to the epoxy that seems to be universally used on other instruments.

Another material to try is a terpene based stripper like Simple Green. The terpenes don't have the dangerous properties of methylene chloride, but it may take a LONG soak to get the lacquer to flake off.

I just want to mention that the rate of corrosion on these horns is not something you should panic over. It will take DECADES for the oxidation to eat through even a thin gauge metal like a slide let alone a thicker bell. Unless you live in an area of high volcanic activity with storng acidity in the air I wouldn't panic over the appearance.

[BaritoneJack]

Thanks for the warning, Bruce - though I doubt I could buy anything that lethal in a regular hardware store in England; it would probably only be available to trade buyers. I downloaded the Material Safety Data Sheet for the one I have, and there's no Methylene Chloride in it.
Re. the hot water; that could take a bit of setting up, as I don't have a bath in my flat, only a shower. But I'll give it a go on the tuning slide, and report back as to what happens.
With best regards,

Jack

[BaritoneJack]

The latest is that I tried my paint stripper, following the instructions to the letter (give it a complete coat, leave for one hour, then another coat, and another hour) - and it didn't so much as raise the tiniest bubble. I then read up on a product called Nitromors - which used to be capable of shifting barnacles off a ship's hull - and the current customer reviews vary wildly. Some say it did the job, but was very slow, others said it didn't touch their paint at all. From what I've read, I suspect that, in the past, it contained Methylene Chloride, but now it doesn't - and so it appears that (like the paint stripper I tried) whether or not it works depends on the exact constituents of the paint.

I did manage to soften the lacquer on the tuning slide by soaking it in hot water, and then using a pot scourer to take the softened lacquer off - and I saw how the corrosion was eating into the metal underneath the lacquer. It appears to show the same characteristics as the brackets on my Harley (see above) in that the corrosion seems to be faster where its not fully exposed to the air, but is shielded by the lacquer. This is a photo of the top of the tuning slide, which had several transverse scratches. You can see the way the corrosion has spread sideways - but look at the areas marked with red arrows, which have what looks like a pale gold border round them (see the picture below).

Picture 3.jpg

Imagine that the arrow-marked areas were plateaus, standing slightly above the rest of the tubing; now imagine that reversed, so that that area is set below the rest of the metal; that's how it is. And what bothers me the most is this; you can't make it out from the picture (even though it's about 15 - 20 times full size) but look at the lines inside the corroded areas; they are where the original scratches were, and where the brass was fully exposed to the air. Those lines have corroded less than the areas on either side which were still covered by the lacquer.

Now, I grant you that the depth of where it's been eaten away is only 2 or 3 thou - but it still appears that the corrosion is happening faster under the lacquer than it is on the exposed brass. To me, that means I have to get that damn lacquer off.

I had another idea last night; acetone. As used to remove nail varnish. And straight acetone is readily available on line. But before sending off for a half litre, I thought it worth trying an experiment - so this afternoon I'll nip down to the supermarket and buy a bottle of nail varnish remover, making sure that it's one with acetone in it (some don't have it).

A few years back, when I had a diesel Land Rover (and was really hard up) I started running it on sunflower oil, and got a tip from somebody else that adding about 3% of acetone would help it fire up more readily on cold mornings, so I did some background reading on acetone - which is how I know they use it in nail varnish remover. I didn't put the remover in my fuel tank, as it also contains glycerine.

Nonetheless, whether it contains a bit of glycerine or not, I reckon that a few minutes swabbing the nail varnish remover onto the lacquer should prove whether acetone will shift it or not. If it does, I'll order up a bottle of straight acetone, and use that. If that fails, I'll go for the nuclear option - a long soak in warm to hot water, followed by the finest grade of steel wool, and then back to metal polish.

Watch this space!

Jack

[BaritoneJack]

I'm not having much success with uploading pictures, but I'll try for another one - taken with my camera, not just my phone - to show the extent of the problem further down the bell. The white gunge on the right is the (useless) paint stripper; the pale green streaks are not out of focus - they started out as thin scratches, and show how the corrosion spreads sideways.

[BaritoneJack]

The story so far; the acetone didn't have the slightest effect on the lacquer, so I ordered up some '0000' grade steel wool from Liberon - a specialist firm which supplies people like cabinet makers and french polishers. Slow work, but it does gradually get through the lacquer. Though it obviously leaves a myriad of faint scratches over the surface, they aren't so bad that metal polish won't shift them, and bring it up to a presentable finish in the end.
But it's going to be a long old job!

Jack