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Help! - bent bronze casting
ladytrickster -
Sunday, December 26, 2010 - 5:40pm
Casting Need Advice! I made a lovely cast bronze tripod vessel in the style of the ancient Chinese. I modernized the concept a bit, such that the 3 legs extend beyond the top of the 'bowl' (sorry, no image yet). The legs are about 6" tall x 1/2-to-1" wide (tapered) x 1/4" thick, and have a very slight slant/curve. They are joined to the body of the vessel only at the top rim. (use your vivid visual imagination!) [see my Profile Image for an idea of the shape] The piece fell off a bookshelf onto the carpeted floor. Two of the three legs are now bent! Cast metal is strong & the thing weighs over 3 lbs. - so I can't figure how it was even able to be bent. Not just a 'straight' bend, but the curve is distorted, too! Hand-pressure does nothing to move the metal, and not wanting to 'snap' the legs by trying too hard to bend it, I stopped in despair. How am I going to repair this? The entire look and line of the piece is ruined. (I know you need a picture, but I don't know how to post it - help, anybody? re: posting an image) Heating the metal would ruin the hand-mixed mineral patina, and there are 3 gemstones set in as well. Help, anybody about 'bent' cast bronze? This is my very 1st post!  bent bronze casting
ladytrickster -
Monday, December 27, 2010 - 12:56am
Thanks, John! It's great to hear a "metal-voice" !! - And your encouragement. I s'ppose the piece is *not* lost, although I have no mold for it (more help there?!) Like you said, prob'ly the worst that would happen is un-setting the stones & redoing the patina. I made that one up anyway, in the absence of opportunity to apply 'real' patina: some ground up turquoise, malachite, salt, vinegar, whatever my feeble imagination dictated at the time... The piece is cast in true bronze: 90% copper/10% tin alloy. It's pretty tough, tho prone to porosity in casting, as you said. Good info about the power of "inertia." (I have some of that myself, pretty bad. ha.) But I really was surprised that a little fall would bend it - then it happened twice! There's nothing gonna bend this little treasure except annealing & skillful pounding... *after* I use a saw to remove the legs! They have a real nifty texture. (take a mold!!!)With the precious tripod 'in pieces' it'll be easier to get a 2-part mold of the 'bowl' part, also... When I get around to the repair project - will the patina remove itself in the process of heating? Or should I use some other method? I'm not sure how evenly the piece will heat - some areas are much thicker by proportion... It's also very detailed, and nicely pockmarked, in an 'ancient' sort of way, so methinks sandblasting back to a clean surface isn't feasible. So, what do you advise as the best way to remove 'crusty' patina first? Do I ask enough questions? har. Thank you a bunch in advance. I'm still a partial 'dummie.' BTW - What is Everdure? also BTW: haven't visited yet, but your website address includes reference to "mandalas" - one of my very favorite things in the world. I look forward to seeing what you're up to! Thanks for your advice & encouragement.  broken bronze/making a mold
johndach -
Monday, December 27, 2010 - 2:34am
True bronze or more often "we" call it ancient bronze as that is more the formula used by the ancients (they had sources of tin but not silicon (used in today's art bronzes)or zinc (I do NOT like the zinc for MANY reasons). Did you make or do you have any vent,small filler rods left over from the original casting? If you do and you need to weld it, you at least have filler, though it is still a difficult alloy to weld. If the bends are not "very" bad/sharp/sever I would think I would try bending without heating, or even better, if you have any "left over" casting metal (the 1/4" rods or ???) try bending a piece one way then the other to see how this particular alloy "works". As for bending, and not seeing what this piece looks like, a bit of leverage developed via a piece of pipe or tubing can do absolute wonders. Can make one feel STRONG!!!!!!! I would still stay away from the heat if possible. If there is worry about marring the metal, wrap it in some thinnish leather scrap where the part is going to make contact with the "cheater" (metal pipe muscle assist). A mold, even with the legs on, is NOT a problem. A 2 piece or if needed a 3 piece mold is not that difficult. I would make a difference what mold material you use, I personally like some of the "new" tear resistant silicon mold rubbers as they take absolute detail, can be modified as to rubber hardness, they release from everything, make beautiful waxes and last a good long time,10 years for mercury catalyst or nearly life time with Platinum catalyst. It is also amazing what can be drawn from the mold once cast in wax. Main problem with silicon mold rubber is they do not like sulfides, and bronze "rust" most always has at least some sulfide in it and you get gummy spots in these areas. It is best to coat a bronze piece with some sort of coating. I prefer Bulls Eye varnish as it is alcohol based, it dries fast, removes easily if needed and it works great. I most always also applying a release made for use with silicon RTV's (very different than releases that ARE silicon for use with other types of RTV's). As to "sandblasting" DON'T. If any blasting is needed, use very fine glass beads for the blasting media. That is all I have in my blasting cabinet. If done half way well, you will not be able to see any degradation of the detail on the piece. The glass beads would remove the crusty patina without a problem. In fact, some industries use baking soda and water as a blast media. This combination can remove the paint from a soda can without damaging the can material,,,, just removes the paint..... The only bad question is the one not asked!!!! Everdure is a relative industry standard for cast bronzes. It is copper (about 92% and silicon 7-8%). It casts well, can be machined relatively well, welds beautifully and without visible weldment (if Everdure rod is used as the filler), "used" metal from previous pours can be used up to 40-50% of the mix with no color change (as there are no low temp alloy materials in the E. alloy to burn off during melting), BUT,,,, it is an alloy developed for use in the marine trade (one use area anyway) as once is gets a natural patina (pretty dull and relatively ugly gray-brown) it self protects relatively from further environmental/atmosphere degradation. If looking at our websites, there are 3: MLCE.net bronzes, CTMandalas.com for the mandalas and currently the mixed media. (CynthiaThomasDesigns.com is a site but it is not currently working well but you can see all of it via the Mandala site) Good luck on your art piece. Any questions, just ask. John Dach  I second the motion for
timcos -
Monday, April 18, 2011 - 5:01pm
I second the motion for Everdur. We use it exclusively for all of our bronze castings. As the other fellow mentioned...very nice to work with in many venues. Tim Costello |
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ArtMetal
'bent' cast bronze
If the piece is cast in Everdure I wold say that you can just bend the bent pieces back into shape cold, they should not break. However,what all the metal movement is going to do to the patina is another thing to deal with. If the patina is a "crusty" sort of patina, it may well start to "pop" off. If it is a true chemical reaction sort of patina, it "most likely" will be fine but one never knows.... I doubt that the bent pieces will "snap off", this would be likely if the metal in the bent piece(s) is porous, but again you will not know until you give it a try. 3 lbs dropping for a bit of a height becomes a lot more than 3 pounds and when you also apply the 3 pounds+ of inertial energy on a small point, the pressure becomes a LOT more. Sorry for the problem, but at worst, you may have to un set the stones and redu the patina,,,,,, the piece is NOT lost.
John Dach
john@MLCE.net
web site: http://www.MLCE.net and ctmandalas.com