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Green stick to stir my alloy?


#1

where can I find a green stick to stir my alloy? I’ve been looking
around and no one seems to carry it. Unless it’s under a different
name?


#2
where can I find a green stick to stir my alloy? I've been looking
around and no one seems to carry it. Unless it's under a different
name? 

You don’t buy them. You go out into your yard or a nearby park or
something, and snip one from a suitable plant. Green stick means a
stick of wood that’s still 'green, meaing it’s still full of sap, ie,
taken from a living plant, not dead and dried out. Almost any decent
shrub or small tree’s twig of suficient size and length will work.
The idea is that because it’s still wet with sap, etc, the stick
won’t burn as quickly, and the volatile organic compounds in the
wood, when they do burn, will contribute to a reducing atmosphere
around your melting metal.

Peter


#3

Hi Jimmy,

where can I find a green stick to stir my alloy? I've been looking
around and no one seems to carry it. Unless it's under a different
name? 

A green stick is free, you take it from a living tree.

Just go out the back and remove a suitable size stick.

Don’t use a stick from a succulent, otherwise you will have
unintended granulation.

The method is an old founders trick, the impurities in the melt
stick to the stick. Some things in life are free :slight_smile:

Regards Charles A.


#4
where can I find a green stick to stir my alloy? 

Why buy ??? A sharp kinfe (or saw frame) in the back yard works
really well for fresh green sticks.

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand


#5
where can I find a green stick to stir my alloy? I've been looking
around and no one seems to carry it. Unless it's under a different
name? 

As far as I’ve ever heard, a green stick is just a green stick - a
branch off of a tree that hasn’t been dried. Any stick, any tree.
Well, maybe not oleander.

http://www.donivanandmaggiora.com


#6

This may simply be a case of “English as a secondary language”…

It’'s just a twig of the appropriate size you cut off of a living
plant. Right now, most of mine come off of a young live oak in my
yard that has branches at a convenient height.

Ron Charlotte – Gainesville, FL


#7

I use a bamboo chop stick to stir my alloy.

Works just fine.

Alma


#8

I might be rather careful of using a green stick to stir metal with.

Every year there are fishermen blinded when they use a green stick
to stir lead for making fishing weights. This results in a steam
explosion sending the lead flying into their faces.

I’ve also seen someone pour molten silver into a plaster mold that
wasn’t dry enough and it blew the metal in all directions about 20
feet.

This is one of the reasons you warm an ingot mold before pouring, to
drive off any condensed moisture that might result in a steam
explosion.

So, I make sure only to use a dry wooden rod if I am using it in a
melt. Graphite rod, quartz rod is often used. Some jewelers use a
pencil (graphite rod surrounded by dry wood).

best
Charles


#9

I use a small branch cut off of one of my Apple trees. I like the
smell of it. It reminds me of BBQ.

Ken Moore
www.kenworx.com


#10

Hi Charles,

I agree caution is advised when you melt any metal, but with
adequate observation there’s no reason to dismiss the green stick
method.

Trouble happens when you use a “wet” stick, you leave the stick in
the melt, or you use a species of plant that is turgid with water.
It’s the same reason that the silver, in your example, erupted out of
that plaster mould. Too much water. Water and hot metal are a very
dangerous combination.

There was a aluminium foundry in Melbourne, that exploded and took
out a lot of property. Someone threw a full glass coke bottle into
the molten aluminium, if the bottle had been plastic, the liquid
would have evaporated before it touched the molten aluminium, as it
was the glass provided enough protection to make a lethal bomb.

Melting metal should not be taken for granted.

That PSA said, a green stick is better than a dry wooden stick
(ime), but remember I do gravity pours, and am using Delft clay, so
need the melt to be as best as it can be, no gas, no inclusions, no
impurities… especially if I’m using a lost foam model.

The bonus is that you end up with a carbon stirring rod anyway (or
some fuel for the charcoal forge).

Be safe these holidays, and seasons greetings.

Regards Charles A.


#11

Happy Holidays All,

I have been using the live green stick to stir for 43 yrs and it
works well. My metals professor told me about the technique in
college. He told me in casting foundries he watched as they used a
large tree branch to stir, it burns out oxygen pockets and lowers
possibilities of pits in the casting. My current azalea brushes
haven’t missed the twigs I use.

Kristina


#12

For what my memory is worth - not much maybe - I recall reading some
ancient source on this - Vitruvius? Agricola? - I was studying
something to do with bronze casting I think - It must be 40 years or
more since I read it, so forgive me and let’s not bicker over
details. The point is that it wasn’t just a generic “green stick"
but a particular species which was recommended to stir alloys.
Again, for what it’s worth, my recollection is that Alder was the
wood specified. In general I think such specificity is too easy to
dismiss as some kind of ignorant superstitious repetition of a
random lucky accident. Perhaps Alder was the nearest or most common
stick of wood at hand when that technique was discovered or
recorded. If you bear in mind that the ancients did not have the
"advantage” of our modern chemical knowledge, that the very
existence of oxygen itself was not discovered and described until
the eighteenth century, you can see that the ancient Romans or even
the renaissance craftsmen could not have understood the supposed
function of the green stick as we do. The concepts of “oxidizing” or
"reducing" would not have formed their understanding. What they did
have, which many of us today do not have, is a much better-developed
sense of observation and practiced memory for details - things which
many of us do not bother with today because we can easily look
things up in books, or google from so many other sources. We can
apply our school-learned theories - scientifically proven - and in
some ways that is bound to be much more efficient. For example,
applying modern theory, one of the people who wrote in explained
that the organic compounds in a green stick would, in effect,
scavenge oxygen and thus provide a beneficial, relatively
oxygen-free environment. I see no reason to quarrel with this. It
conforms to chemistry as we know it today and makes good sense. I
suppose any green stick used would have this same effect to some
degree. The question that piques my curiousity is why one particular
species was considered the “right” one to use. This is where I am
comfortable giving considerable credit to the experienced eye of the
ancient practitioners because, rather than being seduced by an
intellectually correct theory, they would have relied on their
personal observations to search for and detect the relative
effectiveness of one species of wood over another. Different species
have different assortments or proportions of organic compounds - so
that may have been the critical factor in their choice. Also,
picking up on a warning sent in by another writer, it may be that
the mechanical or cellular structure of some woods render them more
or less likely to create steam explosions when dunked in molten
metal - so the choice of wood species may have nothing at all to do
with producing a reducing atmosphere, but with providing a practical
measure of safety in the workshop. Just think how some woods in a
fireplace burn slow and steady while others crackle and spit.

The deficiency in my ramblings here is that I cannot recall for sure
if Alder was the wood recommended, or some other - and the
incremental advantage may be relatively insignificant. One of you
may wish to pursue this question further. I doubt this is sufficient
reason to establish a sub-industry harvesting and shipping alder
sticks to alder-deficient parts of the country. But I do try to give
a full measure of respect to our forebears who, without the benefits
of our modern understanding, used the full abilities of their minds
and eyes to accomplish marvellous work- some of which still cannot
be equalled today. They worked very hard, with primitive tools and
under harsh conditions. With so much labour and capital invested in
their work they were not likely to be careless in recording and
passing on their recipes and techniques. If they say “alder” I’ll
use alder first.

And very merry Christmas, Hannukah, Solstice, Kwanzaa, Diwali,
Pastafarian Monster Spaghetti Day, Ramadan, and New Years to you
all.

Marty in Victoria


#13

The use of a green stick by itself to stir molten metal is not going
to do much good but shouldn’t do any real harm.

This practice is from the copper foundry and is called polling.
During smelting copper absorbs oxygen and forms cuprous oxide in the
melt, it also absorbs hydrogen, carbon monoxide and sulfur from the
fuel burned in the furnace. If there is an excess of oxygen (cuprous
oxide) in the copper it will not hold the reducing gasses as hydrogen
will reduce the copper oxide to pure copper and water vapor which is
not soluble in the molten copper and bubbles out. Likewise carbon
monoxide reduces the copper oxide to pure copper and CO2 which is not
soluble in the molten copper either so it also bubbles out. Sulfur
will react with the molten copper and cuprous oxide and form copper
sulfide sulfur dioxide gas both of which will stay in the melt with
the sulfur dioxide forming gas bubbles (porosity) when the copper
solidifies. So sulfur should be kept to a minimum if at all possible

During the smelting process having an excess of oxygen in the copper
is good as it keeps the copper from absorbing the hydrogen and CO
that are present in the furnace. Unfortunately more than a small
amount of cuprous oxide in the cast copper makes it brittle and hard
so one needs to reduce the oxygen content to something in the.005%
range before casting. This was done by “polling” the melt, first a
layer of pulverized coal(low sulfur), coke or charcoal was spread
over the surface of the molten copper then they would literally
immerse small(3’’-7" in diameter) trees (poles) that had been
stripped of branches into the molten metal. They would have to be
chained down to hold them down into the bottom of the crucible. The
boiling off of the steam along with the other volatiles would
vigorously stir the metal and the organic (carbon) compounds would
react with the cuprous oxide and make CO2 and pure copper. The CO2
and Steam would bubble out of the melt and reduce the oxygen level.
During this process the foundry operator would take small samples to
see how they solidified. If the ingot had a depressed surface it was
still too high in oxygen content and known as “under pitch” If the
ingot had a fairly level surface with a series of ridges in it it was
at the right level of oxygen and called “tough pitch” to indicate its
greater strength in later hot and cold work. If the polling went on
too long then the copper would begin to absorb hydrogen and CO and
upon cooling would off-gas which would result in extrusions of raised
surface features on the ingot and internal porosity, this was said to
be overpolled or over pitch.

So since most of us are not melting copper but some alloy that has
copper Anyhow in our little bitty melts we obviously can’t take
samples to look at how the process is coming along so it is hard to
say when enough poling has been accomplished and unless you use a
crushed charcoal cover the melt during polling it will just continue
to absorb oxygen so no amount of polling will do any good. You are
probably better off using a sufficient amount of a casting/melting
flux to provide a cover over the melt and stir only briefly with a
carbon rod just before casting.

James Binnion
James Binnion Metal Arts