Metalsmithing Techniques, Tips, and Tutorials: Introduction to Broom Casting

20 Apr 2012

 

Pebbles by Beth Rosengard. Diamond and black drusy garnet earrings.

On my ever-growing list of more advanced metalsmithing techniques to try, casting--specifically broom and cuttlefish casting--is near the top. The surprise and randomness of the results appeal to me just as much as their natural beauty, and I appreciate the fact that the resulting textures, patterns, and shapes really can't be achieved through any other metalsmithing techniques. So if you're up for a little adventurous metalworking and aren't afraid of surprises (or fire . . . ), join me in learning broom casting!

Broom Casting Tutorial
by Brad Smith

Materials: 

natural-bristle broom (straw or corn stalk)
about 1' of binding wire
borax flux
metal (silver or gold)
crucible for melting metal
carbon rod or clean solder pick
torch with a large tip
two C-clamps
clean 5-gallon bucket
water

Steps:

 

1. Saw off the broom handle, leaving a stub about 2" long. Cut all stitching from the broom bristles and bind them with wire (about 5" to 6" down from the top of the bristles) into a 3" to 4" thick round shape.

2. Fill the bucket about two-thirds full with water and soak the broom bristles for at least 30 to 40 minutes or overnight.

3. Remove the broom from the bucket and fasten the C-clamps to the broom handle stub so the broom stands straight up. Refill the bucket with water to two-thirds full and stand the broom upright in the bucket.

4. Melt 1 to 2 oz. of metal in the crucible until it melts into a liquid, balls up, and rolls around freely in the crucible. Add a pinch of borax flux when the metal has melted and mix with carbon rod or clean solder pick.

5. Keeping flame on melting dish, pour a slow steady stream of metal into the bristles while moving the crucible in a slow spiral motion over the bristles.

6. Douse the smoking broom with water.

7. Unbind the bristles and retrieve as many castings as you can. Select what you wish to keep, rebind the broom, and cast again, remelting any undesirable pieces with additional metal. When you're completely finished casting, go through the bristles carefully to retrieve small bits of overlooked metal.

8. Before incorporating broom-cast pieces into metal jewelry, clean and pickle them thoroughly.

You can learn more about broom casting and see examples of broom-cast metal jewelry in the complete article, Casting Metal with a Broom by Helen Driggs (in the June 2007 issue of Lapidary Journal Jewelry Artist magazine). Helen interviews Beth Rosengard, a metalsmith and jewelry artist who has, as Helen accurately puts it, "transformed this delightfully low-tech approach to molten metal into a sophisticated level of artistic expression."

 

Autumn brooch by Beth Rosengard. Koroit opals and citrine.

The Swan by Beth Rosengard. Necklace of baroque freshwater pearls and diamonds.

Like Helen, I got excited by the possibilities of modifying the broom-casting technique (as I usually do) into other kinds of metal castings, such as shells, twigs and bark, or maybe even moss. "You can use anything that will burn," Beth says. "And the material doesn't necessarily have to be bundled. For instance, you could pour molten metal over rice! Some materials might burn too fast, though, even when wet--like ferns." Okay, maybe moss won't work . . . but I'm still going to try! The idea of experimenting and creating unique shapes appeals to Beth, too, who admits that she "poured molten metal into a bucket of ice and ice water" and "got some very cool, organic splat shapes." I bet!

Broom-Casting Tips and Safety

  • Beth shares the value of doing broom-cast pours with a partner, who can help with adding the borax flux or dousing the broom after pouring.
  • You can broom cast with "any metal that you're able to melt to a liquid state: in other words, any metal that you might use in lost-wax casting," Beth says.
  • Start with silver as a beginner, and if you really want the look of broom-cast metal in gold, you can plate it or thin the silver and "then use lost-wax casting to reproduce them more efficiently in gold," Beth says.
  • And what about broom-casting safety? "First and foremost: pay attention to what you're doing and where you're pointing the torch," Beth says. "It's all too easy to lose concentration and burn yourself or someone else."
  • Beth recommends doing broom casting outside, preferably on concrete. "It's possible to miss the broom or bucket occasionally," she says, "so stand back and watch out for spraying bits of hot metal."
  • Remember to douse the broom after each pour to keep it from burning up too quickly as well as to keep you from getting burned when you pick through it to find your cast-metal pieces.
  • As Brad says in his tutorial, broom casting is a metalsmithing technique best done outdoors, "because wet straw is very 'aromatic' when burned!" 
  • Beth's final words of wisdom for beginning broom casters: "Wear goggles to protect your eyes. And wear shoes!" 

To learn more about casting and all kinds of other metalsmithing techniques, check out Lapidary Journal Jewelry Artist magazine--and back issues are on sale now in the Jewelry Making Daily Shop!

Do you broom cast? What metals do you use? I'd love to hear more about your broom-casting experiences in the comments below. 


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Comments

on 21 Apr 2012 6:13 PM

Great post thanks !

Rob Morrison wrote
on 22 Apr 2012 8:10 PM

This is a generous site, and offers many good free tips as well as good publicvations, so here is a tip of mine in return for those who like to use Liver of Sulphur in patinas.  The solid stuff goes off after time, but I can keep it almost indfinitely by making up solutions of various strengths and then freezing them in small bottles, leaving a space at the top under the screw cap.  The space stops the bottle from bursting as it freezes, but also allows you to add a bit of water to the frozen block to melt the top layer. Pour that off and use it, refreezing the bottle. If the remainder never thaws, it will keep, apparently forever.

Rob

jewel1152 wrote
on 22 Apr 2012 8:22 PM

I like to broom cast in silver. Here's a good tip for those trying it: When my friends and I broom cast, we cut the straw from the broom and make a bundle about 2" across. We bind the top and the bottom with binding wire  (not too tightly) and place the bundle in a container with some water. After pouring silver, the bundle is quenched, the wire is easily slipped off the bundle, and the straw can be spread out in a tray to recover the silver castings without losing any in the base of the broom. Re-bundle and continue. A typical broom will yield 2 -3 bundles of straw.

tkstiles wrote
on 30 Mar 2014 7:02 PM

Thanks for the idea. I'm always looking for something new. This opens me up to a lot of other things that might create an interesting pattern. I'm looking forward to reading more articles. Thanks  @tkstiles.com

tkstiles wrote
on 30 Mar 2014 7:04 PM

Thanks for the great idea. I'm always looking for something new.  This gives me a lot of new ideas about textures, oh the possibility's. Looking forward to reading more articles.

TammyJones wrote
on 31 Mar 2014 4:57 PM

Glad you guys like it! Thanks for sharing!

Tammy