Wednesday, July 20, 2011

Witness Marks









Yesterday I started a small sculpture project which required seven pairs of elements. The pairs are similar but not identical so I stamped reference numbers to keep the pairs matched. This one example of what I call a witness mark. They may not be readily apparent in the finished piece but theoretically a forensic examination might reveal them.

After a little checking I found this phrase can be used to express quite a range of subjects. The online Double Tongued Dictionary, which describes itself as “a lexicon of fringe English focusing on slang, jargon and new words,” gives this definition:

“witness mark n. generally, an intentional, accidental, or naturally occurring spot, line, groove, or other contrasting area that serves as an indicator of certain facts; in geography and surveying, a blaze, cut, hole, paint splash, or message written on a post, tree, rock or other guide to indicate a boundary, feature, or significant point on land, especially on a witness post; in construction and manufacturing, a line, groove, score, notch, cut, or written indicator made on the surface of material to impart information, such as where to cut or join; in forensic investigation, a surface groove, smear, stain, abrasion or other feature that can serve as evidence.”

I’ve used the term a long time. I think I learned it when I was doing woodworking. I distinguish it from a “process mark” which may be detected on close examination but not intentionally placed - just a surface mark related to the tooling used.

I make witness marks mostly to demonstrate the proper alignment of a tool or jig. I remember watch Tom Clark forge a hardy and fit it to the anvil - it only fit in one orientation so he made a mark on the side which should face the horn. I call these “registration marks.”

I also don’t think of transient marks as witness marks. Silver pencil, paint marker, layout fluid, presto pen and soapstone marks are quite useful but disappear as the work progresses and they are no longer helpful. Interestingly, I don’t know if there is really a proper name for that group but I’m going to call them “layout marks”. Even a center punch mark, which could be a permanent thing, disappears if it serves as a place where a hole was drilled.

Likewise, I think of touchmarks as being in a separate special category as well as the numbers stamped to indicate a pieces’ place in a series.

So, what makes a good witness mark? This is the rhetorical question that keeps me going. Usually, I use a punch. Usually the punch has a sharp round tip. Usually it is a center line mark. I was taught that a sharp square punch mark is easier to see in the fire than a round one but I really can’t say it has made enough difference for me that I make square punches which are more tedious to sharpen.

If I think I will have a hard time seeing the mark in the fire I will use a round punch to make a frog eye, my favorite - see the images, or use a gate fuller or guillotine tool to place shallow fuller marks on opposite sides for reference. Of course, these need to be used in areas where they will disappear with subsequent forging.

A scribe is nice for precision cold work as are transfer punches. Sometimes a chisel cut works well, sometimes a shallow file or saw cut or a zip disc nick. Occasionally I just put bars in the Hossfeld bender and make a slight kink to mark a transition spot. As John Wayne said in "Hondo”, "A man ought'a do what he thinks is best."

So, I think the name of the set is Witness Marks and the members of the set are all those other examples. At least that’s what a splitter would say.

I found this by searching for witness mark but I would call it an illustration of process marks: Cute animation

http://www.kanabco.com/vms/glossary/w/witness_mark.html

http://www.persimmonforge.com/

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