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Broom casting


#1

Hi Alice,

I teach workshops at our local lapidary club and this past July
taught a class on broom casting. It is an easy, low tech way of
using up scrap metal and can result in some interesting formations.
I have a successful line of jewellery that incorporates broom
castings.

Equipment:
-scrap metal (I use silver) free of ferrous metals (no broken saw blades),
solder and other debris
-crucible with long insulated handle
-borax
-fuel source
-corn broom, cut off handle
-large bucket
-water
-safety goggles

Method:

  1. soak broom for several hours (or even days)
  2. stand broom, bristles up, in a bucket
  3. add cold water up to the level of the bound end of the broom
  4. prepare crucible with borax and torch
  5. add small amount of scrap silver to crucible, add borax
  6. heat metal until it is fluid
  7. hold crucible close to broom and pour the metal into the bristles, keep
    flame on metal while pouring
  8. place broom under water to quench the metal
  9. remove casting

Experiment with different amounts of metal, different lengths of
bristles. The castings can be used in whole or in part. Other
elements can be added, stones can be incorporated. Use your
imagination.

Good luck, Sydney


#2

Recently I tried my hand at broom casting - what a blast!! I melted
some Argentium sterling scrap and got very blobby, heavy results.
Tried fine silver and got slightly more refined castings, but not as
fine as I want. I melted the silver until it was perfectly round and
throwing off little sparks, then poured over damp broom straws, but
the resulting pieces are 3x heavier and sturdier than I prefer. How
does one get thinner, finer castings? Does more boric acid make it
more or less blobby? How many times can one remelt the Argentium
before its melting properties are affected? If it gets burned, or
melted too many times, is it still OK to send it in for refining? I
realize some of these questions can be answered by just screwing
around, but with so many variables thought it might be more efficient
to gather more info before ruining my scrap.

Blessings,
Sam Kaffine


#3

I find that in broom casting, a lot is determined by how tightly you
bind the straw, and how much silver you pour at once. The tighter
the straw, the daintier the cast bits, especially if you can tip out
only a small dollop in any one spot.

I like to bind the bottom of the (well-soaked) bundle tightly, the
top just a bit looser, but experimentation is the way to go. K

I have only used regular sterling, but I have re-melted many times
without apparent issues in what is essentially a funky process
anyway.

Noel


#4

Sam, we hold a ‘fun casting’ workshop each year at our school so
students can learn ‘other’ properties of metals. Broom casting, bean
casting, salt casting and splash casting are all attempted. The two
most popular are broom (straw) and salt.

There are two ‘secrets’ to broom casting. One is…don’t attempt to
do too much metal at once. Keep it light.

The second is in the wrist. Do not hesitate in one position but
rather sweep your ladle across the surface of the straw being sure to
pour a thin stream of metal the whole time. I teach students to flick
their wrist upward at the end of the sweep just as the metal runs
out. We get excellent strings.

You should also experiment a bit with the tightness of the straw.
Too tight and the metal will blob up, too loose and it will drop to
the bottom.

Cheers from Don in SOFL.


#5
  1. the cooler the water, the tighter the broom and more voluminous
    the bundle and the higher the distance from ater to crucible are all
    variables that help in getting closer to the results you want.try
    adding a mixture of ice and water to the bucket (enameled metal or a
    ceramic vessel preferable). You may also try arranging the brromstraws
    into varied lengths, or other arrangements and soak them first in the
    ice/water to add a modicum of control to the results. Writing down
    your methodology will help you get similar results when repeated. You
    may also try adding rock salt to the ice & water to lower the
    temperature of the mass into which you will pour your metal.

  2. More boric acid into the crucible will not make it more
    controlable- the more you add above the amount necessary to add a
    degree of cleaning to the scrap (if using fairly clean scrap a pinch
    or two is all that is really necessary.the main thing in using scrap
    is to make sure you have no remaining solder stuck to the scrap and
    that it is not oxide coated before the remelt- if it is drop it into
    your pickle, allow it to act, rinse &neutralise with sodium
    bicarbonate solution, then rinse again and dry before remelting). Too
    much boric acid or borax results in a mass of “glass” that must be
    melted in order to make the metal pourable: if you have coated the
    crucible with borax and added more to help refine the scrap it pulls
    the coating off the crucible ( in fused silica/clay crucibles-" the
    white ones") and the result is a mass of molten borax slag rolling
    around the metal- it can clog a hole in crucibles designed for
    casting machines rapidly- though I personally prefer those style of
    crucibles for direct open casting as one would use for cuttlebone,
    broomstraw, pine needle, shell, and other direct casting methods as
    it allows the metalsmith to direct the metal to the “mould” easier
    than if using an open dish style crucible.

  3. Silver will remelt many times however, the germanium may burn off
    if melted at too high a temperature. I would say 3-4 times is
    completely OK, Check out cynthia eid’s website for more info on
    argentium- I use fine silver almost exclusively in my studio adding
    germanium only when I want the properties of argentium (without
    paying for pre-fabricated materials from a vendor) because with
    buying only one metal I can alloy anything necessary that equires
    silver without any of the problems added copper lends.

  4. it shouldn’t get burned! If you get something (a mass) that looks
    burned it is probably something other than the silver that was in the
    scrap- most likely solder or some zinc as when it is overheated it
    appears dull and black or a dark grey. Pickle will sometimes remove it
    or a good bench knofe can scrape it off the surface, but the silver
    shouldn’t burn up - nonetheless it is still precious metal and
    suitable fro refining.

  5. if you have “dirty scrap”, particularly low karat golds or
    sterling you can make a refining flux with powdered charcoal and
    ammonium sulphate ( sold as a “tinning block” for electric or butane
    soldering irons at stained glass supply stores) in a proportion of
    about 5:1 powdering the activated charcoal is the way to go with this
    flux as you want it as fine as possible. Note that the ammonium
    sulphate is a humectant easily drawing humidity from ambient air so
    keep the remaining block and the mixed flux tightly sealed in a
    non-metal container. Mix only an ounce or so at a time as a pinch is
    all needed for refining gold or silver scrap or when you are pouring
    a large amount of scrap into an ingot or rod.The yield will be a
    bright tough ingot.Anneal then mill into whtever is needed.Keep
    annealling as it gets work hardened by running it through your
    rolling mill, hammering it out, etc. If you have more questions about
    direct casting feel free to contact me off list…rer


#6
I find that in broom casting, a lot is determined by how tightly
you bind the straw, and how much silver you pour at once. The
tighter the straw, the daintier the cast bits, especially if you
can tip out only a small dollop in any one spot. 

I agree with Noel. And, I might add, it also depends on the size and
shape of the broom straws.

It seems to be difficult to find real straw brooms nowadays. The
last time I did any broom casting (last year), what we had were sort
of like witches brooms, but with flat straws. Gave some interesting
results!

Margaret


#7
How does one get thinner, finer castings? 

You can try using a finer straw, as in a whisk broom. If you have
access to pine trees, some varieties have needles that are conducive
to a more delicate casting. Pack them the same way as broom straw,
and make sure your pour is hot enough to penetrate into the bundle.
Experiment with the density of the straw or needle pack. If it is too
loose, your silver will drop like a rock to the bottom. After an
unsatisfactory pour, I tried pickling the silver before melting it
again, and have had better results. Haven’t used Argentium, but have
made some very interesting pieces… Dee


#8

Find a local farmer’s market to see if someone grows what is called
"broom corn". It is an ornamental corn from which the brooms used in
the “13 colony days” were made. It is perfect and I am out of it!
Next year I will grow my own…broom corn that is, lest that be
misunderstood.

Barbara


#9
It seems to be difficult to find real straw brooms nowadays. 

Supply stores that sell to straw hat makers, chair caning, that kind
of thing, will sell them. They’re also sold to people who do
marbling.

Elaine
CreativeTextureTools.com


#10

The League of NH Craftsmen runs 8 shops and there is usually a broom
maker around. Contact them at Concord, NH.


#11

Interesting. I live in South Florida and one of the most popular
supermarkets here is Publix. They carry straw brooms for under $8.

Cheers
from Don in SOFL.


#12

A couple of years ago, I was in Gatlinburg Tennessee. I bought some
of the hand carved handle brooms for house warming presents. The
broom-maker had enormous amounts of broom straw trimmings on the
floor. When I asked to have some, he laughed and said I could have
as much as I wanted. So, go visit the crafts shops making brooms, buy
one or two for luck, and collect the scraps. It’s good for everyone.

Judy Hoch


#13

My most heartfelt thanks to all who responded with broomcasting
advice. The wealth of knowledge and generosity of spirit I encounter
through Ganoksin continues to impress and amaze me - wouldn’t it be
nice if the whole world worked this way? Imagine walking into a
lawyer’s office, or sitting in the doctor’s office, and getting the
same kind of generous, professional advice found on this site -
free!! My thanks again to Don, Noel, rer, Dee, Magaret and especially
Hanuman for making this possible - I’m headed down to the studio to
torch more straw!

Blessings,
Sam Kaffine