Removing Green Spots (Verdigris)
Although brass doesn't rust,
there are still a few ways in which it can corrode. For the most
part it's relatively harmless except in extreme and rare circumstances
- but it can leave your horn looking rather shabby.
If you took a piece of plain brass, gave it a
shine, and then hung it up on an indoor wall for a few years it
would eventually (and quite slowly) tarnish. Its bright, yellow
sheen would fade and it would take on more of a matt appearance
as the colour slowly faded to a sort of straw brown. This is perfectly
natural process called oxidation, and for the most part it's merely
considered an inconvenience if you're partial to keeping your bits
of brass nice and shiny.
when you change the environment to include contamination of the
brass by moisture, weak acids, pollution and various organic compounds
- it can all get rather messy in a very short space of time. Assorted
spots and blemishes of various hues may appear - along with the
distinctive green spots that are known as verdigris (pronounced
Chemically-speaking, verdigris is copper carbonate
(typically with a few other chemicals thrown in for good measure)
and its appearance is a cause for concern because it looks rather
unsightly and can be difficult to shift...and if left to its own
devices for long enough it can damage the brass. Granted, it'll
take a very long time indeed for it to do any significant damage,
but it can certainly leave a pock mark behind if it's not dealt
with in relatively short order. So it clearly pays to get rid of
the stuff as soon as you spot it. However, this isn't always an
easy task because it's quite tenacious - and will shrug off the
usual methods of cleaning. You'll need to get a lot tougher to get
rid of it and, as we'll see shortly, this can have implications
when it comes to preserving the finish of a horn.
It probably goes without saying that prevention
is better than cure - and without getting too bogged down in technicalities
it's sufficient to say that if you put away a bare brass horn (or
one with some missing lacquer/plating) when its wet, you're effectively
sowing the seeds of verdigris. Having a horn made from nickel silver
is no defence either - it's still liable to attack, though to a
lesser degree. Hence the need to ensure the horn is dry before shutting
the lid on the case.
Unfortunately this isn't always practical; the last thing you want
to be bothered with at the end of a gig is having to mop out the
bore of the horn...and then wipe down the exterior. A workable compromise
is required, and it's usually sufficient to whip the horn out of
the case when you get home and leave it to stand for an hour or
two somewhere moderately warm and dry. It probably won't completely
prevent the formation of those nasty green spots, but it'll go a
long way to slowing them down.
Ultimately, then, most sax players are going to
have to deal with verdigris at some point (or pay to have someone
else do it) - and the aim of this article is to show you what methods
are most effective...and to highlight the pros and cons of each.
are two ways in which verdigris can be removed; the first is by
mechanical action - which includes scraping, brushing, abrading
and polishing. The second is by chemical means, which, as the terms
suggests, involves popping something on the spots which will remove
them without the need for a lot of elbow grease.
We'll tackle the mechanical methods first.
Here's our unfortunate testbed victim for the
first part of this project - an old Super Dearman alto that's seen
better day and now serves as a spare parts donor horn.
It's not that badly affected by verdigris, but you can see a few
green spots here and there on the bell - which for most players
should be pretty typical of the level of 'infestation' they're likely
Infestation isn't really the right word (though what you'll see
later in the article probably qualifies as such) and a more accurate
and useful description would be 'encrustation'. Verdigris forms
in layers; it begins with a base layer which grows outwards and
a surface layer which grows upwards. The surface layer tends to
be quite gritty and crumbly - which means you can remove a fair
amount of it with nothing more than a fingernail.
I've numbered the areas that are going to be treated so that you
can refer back to this shot as a point of reference.
a little before-and-after shot that shows just how much of the verdigris
can be removed by giving the spot (No.1) a couple of scrapes with
a fingernail. As you can see, it hasn't removed all of it - but
the spot is a lot less distinct. If your nails could stand it you
could probably go a bit further (and you probably will, because
it's one of those things that are curiously satisfying).
If you have no nails, or at least none that could/should
be used as tools, you can use a wooden stick or a plastic scraper
(with a bit more care). Don't be tempted to used anything harder
as there'll be a risk that it would dig into the brass.
You might well decide that this level of cleaning
is good enough - and if you spent some time picking over all the
spots you'd make a reasonable improvement to the way the horn looked.
But verdigris tends to grow (given the right conditions), so it
might not be long before you'd be back where you started and have
to do it all over again.
A better bet would be to carry on and remove as much of the green
as possible - and for this we're going to need a little help.
The first thing to do is to clean the affected area. We already
know there's a relationship between brass, moisture and verdigris
- which means that washing the area with water isn't a great idea.
A far better bet is to clean the area with a solvent - and you won't
do much better than cigarette lighter fluid (AKA naphtha).
There are no special considerations to this part of the process
- simply sloosh some fluid onto a dry cloth and wipe it over the
area you wish to treat (keeping in mind that it's flammable stuff...so
take due precautions).
While naphtha isn't generally known for it ability to remove verdigris
you might well find that some of the smaller spots may disappear
- and those that remain will take on a paler, more powdery look
after the solvent has evaporated.
it comes to mechanically dealing with the base layer there are three
options; scraping, brushing and abrading. Scraping tends to be very
hard work, and is the method most likely to result in damage to
the brass - so we're not even going to go there, even though it
can be a very precise method of dealing with individual spots. Brushing
is a lot easier, but you'll need something rather more effective
than a paint brush or an old toothbrush - and the fibreglass pencil
fits the bill perfectly.
You can pick these up quite cheaply from all the usual places online,
or in artist/hobby shops. They're built like a retractable pencil
except that rather than having a length of graphite that extends
from the tip every time you twist the tail of the pencil, a bunch
of tightly-packed fibreglass strands appear. The fibres are quite
hard, which gives them a scouring action and makes them ideal for
the job. However, they're also quite brittle...and this means that
they'll shed tiny pieces in use - and if you've ever handled any
fibreglass before you'll know that it can make you itch like crazy.
It's one of the drawbacks of this method - so take care to avoid
getting any on your hands, clothes, furniture, carpets etc. The
safest bet is to do the job outside, but failing that do it over
a few sheets of newspaper...and try to avoid breathing any of the
Another drawback is that the pencil isn't quite
as accurate as a scraper. As you can see from the before-and-after
shot it's quite hard to confine the action of the pencil to the
spot you're working on - so you're always going to end up with a
larger working area than you might have intended. It'll certainly
help if you keep the brush quite short; anything much longer than
shown in the photos tends to result in the fibres splaying out.
You can see, too, that it's completely removed the green spot -
but in so doing it's cut through the surrounding patina to the clean
brass beneath it. It might look a bit draconian but in fact very
little brass has been removed...though note that pile of potential
itching powder surrounding the job (wipe it off with a tissue dampened
with lighter fluid, then dispose of it immediately).
At this stage you're technically done; the verdigris
has been removed and is unlikely to return unless this area is left
wet for any length of time. Now, I don't mind the matt finish the
pencil has left behind - but you may feel you'd rather bring the
bare brass back to a shine...in which case a quick rub over with
a suitable metal polish will do the job - though it's likely to
widen the work area even more so as it'll also remove the surrounding
Which raises the point that one of the issues
you'll probably have the deal with is that of any surrounding finish.
In that last example the green spot was on a reasonably large patch
of bare brass - but what if it's surrounded by lacquer or plating?
To be frank it's really an exercise in damage limitation. A spot
of verdigris will have long since eaten right through any cosmetic
finish, and the object of the job will be to remove it as neatly
as possible while leaving the surrounding area intact.
you're careful and patient the fibreglass pencil can do a reasonable
job. I treated an area (No.2) dead centre of this patch of lacquer
(there was no verdigris spot on it) and you can see that there's
just a small spot dead centre where the pencil has cut through the
lacquer to the brass below. However, the surrounding area has held
up pretty well. You can't really see it in this shot but the lacquer
hasn't come off entirely unscathed...there are lots of very fine
scratches on it now. As before you could choose to leave it as it
is - or you could finish up with a drop of metal polish. It may
well widen the work area a little, but it would also smooth off
the scratches in the lacquer. The same would be true of a plated
surface - but it would very much be a 'see how you go' job, and
stopping before you removed too much of the finish. That said, it
wouldn't hurt to remove a little of the finish around the affected
area as there could well be particles of verdigris trapped beneath
the surrounding edges.
Much of the above also applies to factory patina finishes. Although
such horns are technically bare brass, the chemical tarnish represents
a surface finish - and you may want to preserve as much of it as
you can. That said, any treated areas will soon tarnish of their
own accord and should more or less blend into the factory finish
over a period of time.
in terms of the 'see how you go' approach, it may not be necessary
to take the spot right back down to clean brass.
I'm working on spot No.3 here, and I've brushed it enough to remove
all traces of green but haven't yet cut through the tarnish that
was lying beneath the spot. In fact I don't really need to - the
green is gone, and going any further would only be a cosmetic job.
But the wider surrounding area is all tarnished...so why bother
carrying on? It's a judgement call that only you can make.
option is to attack the spots with wire wool.
There are many different grades of wire wool, ranging from coarse
to very fine - and for our purposes a very fine grade is what's
required. Wire wool is typically graded using a series of zeros
- with 0 gauge being the coarsest. What I'm using here is 0000 (quadruple
It's really quite fine - so fine, in fact, that it can be used to
bring a shine back to nickel plated keys (nickel being very tough
stuff that doesn't scratch as readily as brass or nickel silver).
It's still plenty tough enough to deal with verdigris, however,
though it suffers from being even less accurate that the fibreglass
pencil. This is, or was, spot No.4 - and you can see that the wire
wool has done just as good a job as the pencil did on spot No.3...but
has removed the tarnish from a much wider area. You could probably
improve on this with some due care and attention, but not by much.
On the plus side, it leaves the bare brass a fair bit shinier than
the pencil...to the point where you might not feel it's necessary
to finish up with a drop of polish.
next method (on that faint spot just to the left of No.4) uses a
combination of metal polish and a stick (in this case an orange
stick). You could use almost any metal polish (Brasso being a typical
example) but I've gone for a paste (Autosol) because it's rather
less messy and tends to adhere to the stick better.
This method is as accurate as the size of the tip of the stick,
which you can shave to size to suit. It leaves the best surface
finish of all but it's a lot slower than the more abrasive methods
discussed earlier. It's also a lot fussier in that the polish tends
to obscure the job in process - so the only way you can gauge your
progress is to wipe the surface from time-to-time and then apply
There are a few variations on a theme. For example,
you could replace the metal polish on the stick with a piece of
fine grade carborundum paper (800 grit would be a reasonable choice).
A piece glued to the tip of the stick would be far less messy in
use than polish and it would cut through the spots much more quickly
- and it'd be quite accurate...but I think you'd soon get fed up
of having to replace the abrasive paper on a very regular basis.
You could, of course, just use the corner of a piece of folded carborundum
Brass brushes are an option, but it's not easy
to find one that's both small and fine enough. If it's too big and
coarse it won't be at all accurate and will leave deep marks in
the brass. Perhaps the best chance of finding something suitable
would be to look in places where they sell accessories for micro
drills (such as the Dremel). Incidentally, and assuming you have
one, I wouldn't recommend using a micro drill with a brush fitted
for this job...unless you really, really know what you're doing.
And while I'm here, a steel brush is a big no-no.
the face of it, the mechanical methods seem to work quite well -
so why bother with chemicals?
Well, it's no big deal to tackle a few green spots that have appeared
on the bell...but what if they're sitting beneath the action, or
even on it. Getting your fingers into tight corners isn't going
to be easy unless you're prepared to remove a few keys - and even
then there's no guarantee you'll be able to clean the verdigris
out of all the little nooks and crannies. In this case a chemical
solution works quite well - the process removes the need for elbow
grease and thus makes it a more practical proposition for dealing
with verdigris in tight corners.
The big problem is that it's insoluble in water,
alcohol and organic solvents - which means that treating it with
any of these standard cleaners will, at best, remove any loose particles
but won't do much about the remainder...which will be stuck to the
However, it decomposes in diluted acids - which means that plain
old malt vinegar (acetic acid) straight out of the bottle will remove
it. This is all good and well, but dabbing loads of vinegar over
your horn is likely to leave it smelling rather piquant for quite
a while - which is why I recommend citric acid for this job. It's
slightly stronger and doesn't have a noticeable odour. It's typically
bought in crystalline form and is usually available from general
hardware stores, as it's quite useful for cleaning jobs around the
house. It's dead cheap too, at barely a couple of quid for a box.
There are a few caveats (ain't there always)
to this method, and I'll expand upon them as we go through the various
stages - but it's worth pointing out from the start that there's
a safety issue to take note of. If you get any of this stuff in
your eyes it'll be unbelievably painful - at least for a little
while. It's unlikely to do any severe damage though - but you'd
well well advised to wear safety goggles. You may also want to wear
rubber/nitrile gloves. The acid won't eat your skin away but it's
not exactly good for it either, and if you have any cuts or scratches
on your hand it'll sting like a sod.
Incidentally, and just for info - verdigris converts into copper
oxide when heated, so it's technically possibly to remove verdigris
with the aid of a gas torch. However, copper oxide is black in colour
- so it probably won't look all that attractive...and as yet I haven't
tested the technique so can't say just how hot you'd need to get
mentioned an 'infestation' of verdigris at the top of this article,
and the horn I'm going to be using to demonstrate the acid cleaning
method is as good an example of it as you're ever likely to see.
It's a TJ RAW (as shown in the opening photo) - which is a bare
brass horn that's finished with a chemical tarnish. It's a popular
finish these days, but one that doesn't really suit players who
are inclined to blow a little 'wet'...or a lot wet, in the case
of this horn's owner. Unless such players are fastidious about drying
the horn off properly after playing, the verdigris will home in
on the bare brass like jazzers round an all-you-can-eat free buffet.
As with the mechanical methods, some pre-treatment
will help to speed things up. If you only have a few spots to deal
with you might want to give them a bit of a scrape first - otherwise
you can skip this step and go straight to wiping over the target
area with some cigarette lighter fluid. This too is probably unnecessary,
but it certainly won't hurt to remove any oily residues before applying
The next step is to make up an acid solution,
which is done by dropping a level teaspoon of the crystals into
a small cup of warm water. There's no need to be too precise about
it - a little more or less either way isn't going to make a significant
difference. Give the solution a bit of a stir to ensure all the
A pipe cleaner bent double is perhaps the most effective means of
applying the acid to the body. You could use a small brush but it
tends to result in dribbles and it lacks the stiffness of a pipe
cleaner - which comes in handy when you're working on stubborn spots.
Dip the pipe cleaner into the acid, drag it over the rim of the
cup to squeeze out the excess then apply it to the spot you wish
to work on. Rub the cleaner lightly over the area - it's a chemical
action, so there's no need to scrub with any real force.
you have a large area to treat it's best to break it down into smaller
sections and treat them in turn simply because it makes it easier
to keep an eye on the process and to watch out for dribbles. Mop
them up with a dry tissue as soon as you spot them, and then rub
over the area with damp tissue followed by another dry tissue. If
you fail to spot and deal with a dribble it won't destroy your horn
- but it may leave what looks like a water mark on any bare metal.
If you can be bothered - and you have the space on the horn to do
so - you can mask off any areas that you want to protect from the
acid with clingfilm. You'll still have to watch out for dribbles,
but it won't be quite such an issue if you miss one or two.
Keep an eye out too for any dribbles that fall onto blued steel
springs. It won't dissolve them, but it may result an a blob of
minor surface rust if left to dry out of its own accord. If this
happens, simply rub a bit of 0000 gauge wire wool over the spring
and it'll clean the rust right off.
I'm treating quite a large area here, and one
that's heavily contaminated with verdigris. What I want to do is
keep working the area - keeping it moist and lightly rubbing off
any verdigris particles that have been loosened by the action of
the acid (note the green discoloration on the tip of the pipe cleaner).
marked out on the photo the area on which I'm concentrating for
two reasons; it's about the largest area that's manageable - unless
you're working on a stripped-down horn and you intend to treat the
entire body - and it'll also serve as a comparison with the untreated
areas at the end of the job.
The process is going to happen at different speeds
depending on how much verdigris the acid has to work on. Lighter
spots may well start to fade quite quickly, but heavier encrustations
are going to need repeated applications - such as at the lower side
of this tonehole.
If you feel the process is getting a little uneven, just wipe a
tissue over the areas where you think you've done enough and confine
further applications to the grimier spots. If it all gets a bit
messy and you can't quite see what's going on, wipe over the area
and apply fresh acid.
It's not going to be an instant process, but when
you think you've done enough you'll need to wipe over the area with
a clean, dry tissue. If you see any marks left by stray dribbles
you can use the tissue to work what remains of the acid over the
affected area to blend it in.
now need to neutralise the acid - and this can be done with tissues
soaked in water or by carefully spraying water over the treated
area. If you really want to push the boat out you can always add
a teaspoon of baking soda to the water to increase the alkalinity...though
I've never found it necessary.
now need to let it all dry off - and if you're in a hurry you can
speed it up by running a hair dryer over the treated area.
Don't be too dismayed if you see light green patches appearing as
the metal dries (below, right). It's unlikely you'll catch everything
first time around, and the moisture makes it harder to see the areas
you've missed or haven't treated enough.
It's very much a case of 'rinse and repeat - though
at this stage you might want to focus on the smaller and more stubborn
spots first, before attacking the larger and lighter ones.
Treat, mop, wash and dry until you're happy with the end result.
Here's the finished area (below left) - and while
it's perhaps difficult to spot the transition on the lower part
you can clearly see the boundary line at the top, just below the
You can see that the treated area's completely free of verdigris
- but it's come at the cost of some change to the original factory-applied
patina. The crystalline structure of the brass is more evident,
as is its natural colour in some places - all of which leaves it
with a more mottled look.
it looks a hell of a lot better than it did - and it's still much
more of a 'vintage' finish than that which would have been achieved
by mechanically removing the verdigris.
There's also a bit of the original finish left behind, which tells
you that the acid cleaning process is very much a surface event....rather
than one that eats into the brass in any significant way.
for further comparison, here's a before and after shot of the area
comprising the A tonehole and the compound bell key pillar - both
of which were severely affected by verdigris.
The loss of the factory finish is rather more evident here - but
as with the low B tonehole area it's still a lot less conspicuous
than abrading the verdigris off and taking the metal back down to
If you have a sharp eye you might spot that the low C# spring (fitted
to the lower side of the compound pillar) has gone slightly rusty
at its base after the treatment. As mention earlier, a quick rub
with some fine wire wool will sort that - and if you wanted to go
the whole hog you could run a blue Sharpie pen over the spring to
restore the colour. Get one with a wide nib. If you get any ink
on the pillar it'll wipe of with a drop of cigarette lighter fluid
on a cloth.
Now that the horn looks a lot cleaner you might
be interested in keeping it that way - at least for as long as possible
(this is kinda why lacquer was invented).
The most reliable solution is to use a wax finish on the body. Renaissance
Wax is touted as a good option, but I've used good quality car waxes
with good results. Anything that's designed to protect paintwork
against the ravages of pollution, water and direct sunlight is going
to shrug off the odd bit of gob. And you can use it on your car.
Addendum March 2020:
posted a link to this article on Cafesaxophone
- where I regularly post news of updates - one of the members (Ivan)
asked me a very pertinent question that wasn't covered in the article:
"Is it necessary to neutralise the acid you use to clean away
verdigris? What would be the consequences if not done?"
It's an excellent question - and one that I admit I couldn't answer
authoritatively simply because I'd never actually tested what happens
in such circumstances. Sure, empirically I could say that very little,
if anything, is likely to happen...but it's always preferable to
have some hard data. So I set up a test.
degreased a section of the bell on the poor old Super Dearman alto
and marked off three sections - as shown on the left.
All sections were treated with the acid mix (as detailed above)
twice over a 10 minute period. Following the treatment the section
marked ++ was left as is, section + was wiped with a dry tissue
and section - was wiped twice with a wet tissue and then once with
a dry one.
The shot on the right shows the results.
No surprises here - the acid has done exactly what it's supposed
to do and removed some of the tarnish from each section.
The horn was then left in the workshop for around five weeks, during
which time it was subjected to various changes in temperature and
humidity. It also got handled and (there's no polite way of saying
this) gobbed on - though to be accurate I tried to reproduce the
pattern of moisture droplets from the keywork by blowing raspberries
at the bell (taking very great care to ensure that no-one was watching...).
after all that time, were there any changes? See for yourself? As
far as I can see there's absolutely no change other than that which
occurred at the time of the acid application - and perhaps a slight
dulling of the cleaned sections due to the natural tarnishing process.
I even gave the joint below the ++ section a lick a while back,
just to see if I could taste any residual traces of acid...but all
I got was that slightly potatoey taste of brass (not nice).
To be honest I was a little surprised. Section ++ was a very tough
test - two coats of the acid solution and a good few nooks and crannies
on the bell joint to soak up any excess - but as you can see, there's
really nothing to see.
I'd still recommend cleaning the acid off - it's the sensible thing
to do - but at least you know that any spots you miss are unlikely
to cause any significant problems.
I think five weeks or so is time enough to see some results - but
just to be absolutely sure I'll leave the horn exactly as it is
and keep and eye on it over the coming months. If anything changes
I'll be sure to let you know. Don't wait up.