What is the best way to remove the shellac residue from the
sterling silver jewellery?
Hi Milt,
The quickest way to remove the shellac and the one which I use is the
traditional watchmakers way of boiling the piece in alcohol. You do
have to be careful as it is easy to set the alcohol afire but, so
long as you don’t panic, it is safe enough! You need a metal ‘boiling
out pan’, fairly deep with a flat top and a handle which doesn’t
protrude above the top of the pan. I made a series of different sizes
from copper pipe end fittings (the plain type without a solder ring!)
to which I silver soldered brass handles. You put the piece to be
cleaned in the pan (after you have broken away as much of the shellac
as possible) and just cover it with alcohol. This shouldn’t come more
than half way up the pan - if it does, use a bigger pan. Now you heat
it gently by holding it well above a flame - the alcohol will soon
boil and bubble strongly - you need to keep moving the pan away from
the flame until the alcohol just simmers gently. If it boils over or
you keep it too near the flame for too long, the alcohol in the pan
will catch fire - if it does, just press the top of the pan flat
against the underside of your bench. This will stop the air getting
to the flames and put them out very quickly. The main thing is not to
panic and move the pan quickly as this may let the burning alcohol
slosh out over the side - then you will have two fires to deal
with!!! I’ve been doing this for 30 years plus and haven’t had a
problem. I suppose you could go the wimpy way and use some form of
electric heater to warm the alcohol but I’ve never tried this. After
half a minute or so look at the piece and you will probably find that
all the shellac has disappeared.
For years I have been removing shellac by boiling it out in caustic
soda…which works great!
That said, today I tried the denatured alcohol in a cup and floated
it inside my ultrasonic to heat it and shake it up a bit. It took
maybe 3-4 minutes and also worked great.
Since both work great I think I’d rather avoid the nasty fumes of
the caustic soda. Also the ultrasonic is always hot whereas it takes
a while for the caustic soda to come up to a boil from a cold start.
I read Ian Wright’s method which sounds like it will work just fine,
but I would rather avoid heating alcohol over an open flame. True,
his method suggests a way to deal with the occasional accidental
fire, but the particularly tricky thing about alcohol fires is that
you usually can’t see the flame, it is that pale and non-luminous.
Thus a person might set his little pan of alcohol on fire without
even knowing it, or spill some that was on fire with dire results.
Years ago I spilled some burning alcohol on my wrist - never knew it
was aflame, couldn’t see the fire, but I sure felt it. Ian Wright
sounds like a cool hand and I’m sure I could deal with an accidental
fire just as he does, but not everyone is as composed when confronted
with the problem he describes, just like some people are scared of
mice and some aren’t. Someone trying to do the ol’ smother-the
-flames-against-the-underside-of-the-bench trick could very well bump
the edge of the bench and slosh burning alcohol down the front of his
pants - or whatever.
There is a device called an “Immersion heater” which is a small
electric heating coil - originally invented by my high school biology
teacher in the 1940’s. There is some common lab procedure in
elementary biology lab which requires heating alcohol. Too many lab
techs and students were setting themselves on fire unknowingly by
using bunsen burners and the like. Thus the immersion heater - to
solve the problem safely. These are very inexpensive and easy to get
as they have long since been adapted for more prosaic uses such as
making a cuppa tea when travelling away from home. You plug it into
the wall and drop the business end into your tea cup and voila!
Boiling water. I suspect a large drugstore would be a good place to
start looking for one. Or a store selling gadgets for travellers.
Marty in Victoria where I just don’t feel like travelling anywhere
far from here.
There is a device called an "Immersion heater" which is a small
electric heating coil - originally invented by my high school
biology teacher in the 1940's. There is some common lab procedure
in elementary biology lab which requires heating alcohol.
Good idea Marty. There’s just one more safety thing I’d like to
mention though for anyone who is planning to use the electric heater
method. Because of the size of these heaters it is necessary to use
much more alcohol than I would in my 1 inch copper end cap and, in
addition, it is not so easy to control the violence of the boiling
alcohol. So, as this will inevitably produce quite a lot of vapour
and droplets, you must ensure that there are no open flames or
burning cigarettes around as the vapour will flow along the bench
and over the edge to the floor for quite a distance around and
could quite easily ignite and produce a broad area fire. Its true
that a pure alcohol flame is virtually invisible but, when it is
contaminated with shellac, (and I save the dirty alcohol for re-use
in shellac removal as it will work for a long time in removing the
bulk of the shellac and the piece can be given a final rinse in
clean alcohol), the flame has a distinctly yellow tinge and can be
readily seen. Even if you don’t feel competent to extinguish any
flames against the underside of the bench, the fact that you have
the alcohol in a high-sided metal pan contains the fire and so,
apart from the fact that the piece you are cleaning would be left
with a dirty residue, you could safely set the pan on a fireproof
soldering mat and let it burn itself out. Covering the pan with any
kind of lid, damp cloth etc, will quickly extinguish the flames.
Having a CO2 fire extinguisher around would be a good idea but you
should use it carefully as I was present when a fireman was
hospitalised trying to put out a simple fire with one. The fire was
in the large fryer of a commercial kitchen and was relatively under
control as the lid of the pan had been closed and was being covered
with wet towels, however, the fireman decided to be proactive,
lifted the lid and squirted the CO2 extinguisher into the pan. The
gas hit the back and lid of the pan and caused a wave of burning
boiling oil which shot out of the front of the pan and all down the
front of the fireman. Fortunately his clothing protected him from
the worst of it but he still had burnt hands and face and was in
hospital for several days.