Thanks to all for your comments. Bob has the advantage of having seen photographs of our square wire, and his observation of flashing on it seems to me to favor slitting over rolling, drawing and swaging. There isn't any way to distribute photos through this listserv, but if others want to see the evidence, please drop me an email ([log in to unmask]) and I can send them as attachments.
Thanks also to Dawn for the Oddy article, which I had not seen. The iron drawplates with multiple holes from 7th-9th century Viking contexts are strikingly similar to the iron drawplates at Ingombe Ilede. (Not that there is any plausible connection between them).
David - thanks for your detailed comments. When is the earliest evidence of the use of swages?
From our perspective, the comments appear to confirm our deductions that uniformly square-sectioned wire over lengths of several meters was not of African manufacture. Wiredrawing was extensively documented throughout southern Africa and the southern Congo by European observers in the 19th century, and there are several archaeological finds of iron draw plates, but all produced circular-section wire. There is also no record of mechanical devices like the drawing bench, of mechanised slitting (as opposed to the use of chisels), or of evidence for the use of swages.
On 12/30/21, 8:22 AM, "Arch-Metals Group on behalf of David Loepp" <[log in to unmask] on behalf of [log in to unmask]> wrote:
External Email
Hi, It's possible to make wire freehand, whether roughly round or square, to a diameter of circa 300 microns (0.3 mm) but 30 microns, a third of a human hair, does test credibility for that period. Once wire has been hammered square to circa 1 mm, one can proceed by stretching, compression (such as burnishing or light percussion) and annealing. Stretching leaves characteristic chevron signs that can by eliminated by compression. Constant annealing is necessary to reduce breakage of the wire. Most jeweler's dies stop at 0.15 mm for standard orders.
Hammered wire is best produced in square sections. Rounding is done at the end by hammering the corners to an octagon section and proceed from there either by fine faceting and/or rolling between flat surfaces. Hammering produces fins at the angles that tend to flake off, leaving slight irregularities in the surface, easily blended out by further hammering. In my experience flaking causes a discard rate of circa 1%.
The use of a swage block greatly helps in producing a regular section with little evidence of hammer marks as previously said in this thread.
Modern rolling mills produce a truncated square section precisely to reduce the production of fins and subsequent flaking. This phenomena, already known for hammering, may have induced the use of the truncated square section on rolling mills at an early stage of its development. It would be interesting to find out when sharp edged square section were first used as a profile on rolling mills.
The drawing bench is certainly the best tool for producing a uniform section of any profile.The advantage of a drawing bench is that the strong steady pull eliminates characteristic "snag" signs caused when an operator interrupts the pull temporarily to adjust the grip. Biringuccio illustrated several wire drawing machines in 1540 although they certainly existed well before that date.
David
########################################################################
To unsubscribe from the ARCH-METALS list, click the following link:
https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=ARCH-METALS&A=1
This message was issued to members of www.jiscmail.ac.uk/ARCH-METALS, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
########################################################################
To unsubscribe from the ARCH-METALS list, click the following link:
https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=ARCH-METALS&A=1
This message was issued to members of www.jiscmail.ac.uk/ARCH-METALS, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
|