Bronze for Sculptures – Silicon Bronze
I only use C65500 high silicon “A” sculpture bronze for my bronze sculptures, such as Dancing Fire #1 (image at right). It has a beautiful gold color, slightly brownish. It can be patinated like copper from light tan to browns, blacks, all manner of greens, reds, blues: in fact, any color imaginable. But why? It is such a beautiful color. I like to celebrate its natural beauty. Coated with the proper outdoor-grade lacquer and the clear coat will last 10-20 years.
In addition, high silicon bronze is easy to mig weld, easy to tig weld, easy to shape, easy to cut, easy to finish. Its only drawback is that it is expensive, about 2x-3x the cost of copper which, in turn, is about 5-6x the cost of steel. You can see why most sculptors are using steel. Bronze has a small market (compared to steel and aluminum): the bronze suppliers have a virtual monopoly and can set the market price.
But there are many, many bronzes available for purchase for retailers and recyclers. Let’s take a look at some of them. Keep in mind that anything added to a pure metal will lower and widen its melting point and reduce crystallinity. Here’s an excellent overview from Atlas Metals, my primary supplier.
Other Sculpture Bronze Metals
CS65100 Low Silicon Bronze “B” has about half the silicon level of “A” and a higher melting point. It has said to have excellent tig welding properties.
CS51000 is a Copper-Phos-Bronze alloy and contains about 5% tin and some phosphorous: the tin increases the corrosion resistance and strength; the phosphorous increases the wear resistance and stiffness. It has an attractive goldish-brown color. It is said to be reasonably good for tig welding. It is stiffer than silicon bronze and often used for springs and electrical contacts with high fatigue resistance. I am planning to try some soon.
C22000, C46400 and C38500 are high-zinc bronzes and technically brasses, stiff, hard to form and difficult to weld. Avoid the white zinc fumes: very bad for your brain and lungs. They are not recommended for tig welding: you may have success with brazing these with a small tip, borax flux and an oxidizing flame.
C95400, aluminum bronze, is very hard, tough and expensive and is usually used for casting only. It has a lovely silver-pink color though. Some bronze casting foundries offer it as a lower cost option – because they make their own from left-over aluminum and bronze. You will need to make your own tig wire or brazing wire from the scrapped runners of the same metal, in order to get an exact match for the alloy. Rio Grande sells rolling mills that can expedite this process. I wonder how aluminum bronze would function outside: I would expect a galvanic reaction between the copper and aluminum when wet.
A few of the bronzes I’ve mentioned are included in the table below, to compare their varying compositions.
|C65500 High Silicon Bronze “A”||97||2.8-3.8||0.5-1.3||1.5||0.8||0.6||0.05||1880 F||best|
|C65100 Low Silicon Bronze “B”||98.5||1.5||0.7||1.5||0.8||.05||1940 F||xclnt|
|C92300 Tin Bronze||85-89||.005||7.5-9.0||2.5-5.0||1.5||0.25||1.0||0.3-1.0||NR|
|C92800 Tin Bronze||78-82||.005||15-17||.80||1.5||.20||.80||4.0-6.0||NR|
|C65620 Silicon Bronze (AMS 4616)||90||2.4-4.0||1.0||1.5-4.0||1.0-2.0||??|
|Phos Bronze CS51000||94.8||–||–||4.2-5.8||.3||0.30-0.35||.10||–||.05||1750-1920F||Good|
|Phos Bronze CS54400||88||–||–||4.0||3.0||.25||.10||–||3.8||NR|
|Commercial Bronze C22000||90||10||.05||.05||NR|
|Naval Bronze C46400||70||30||NR|
|Architectural Bronze C38500||57.0||40||3.0||NR|
Bronze Metals Suppliers
A list of some US retailers for silicon bronze and other bronzes follow. Note that some of them have ‘drops’ and scraps lying around that they would love to sell. Ask if they have a ‘bone yard’ or ‘drop zone’.
- Atlas Metals – Denver, CO – 800-662-0143 (about $10.55/lb 10-1-2015)
- Atlas Bronze – Trenton, NJ 800-478-0887 – no longer has sheet or plate
- NB Metals – Houston, TX 1-800-231-0771 – has remnants in many sizes & thicknesses ($11.25/lb 10-1-2015)
- Copper and Brass Sales (ThyssenKrupp Materials) only sell Naval and Phos Bronze, .003 to 3/16″, 800-926-2600
- Farmer’s Copper -Galveston, TX – 800-231-9450 – inventories C65500 in sheet and plate ($10.43/lb. 10-1-2015)
- Alaskan Copper – Seattle, WA – 206-623-5800
- Metal Suppliers Online – Hampstead, NH 800-380-1470
I have spent a lot of time researching bronzes and wondering if there was a lower-priced, easy-to-use alternative to high silicon bronze. There really isn’t, at least not for me and my sculpture fabricating needs. I hope this saves you the research time and effort.
More: How to Mig Weld Bronze
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