I use several basic concepts from structural geology in trying to understand and control shape change in hot metal as it is worked. This essay is an attempt to share some of these concepts as I use them while keeping perspective of the fact that my work is creative rather than analytical.
Structural geologists study metamorphic rocks that have been deformed by tectonic forces, gravity, and heat inside the Earth. They often want to figure out the story of deformational events an outcropping has endured in order to study the geologic history of an area, a mountain range, or an entire continent. The first step in studying deformed rocks is often a search for strain markers, which are deformed objects in rocks that allow their original shapes to be inferred from their present deformed shape. Strain markers can be crystals, fossils, pebbles in sedimentary layers, gas bubbles in volcanic rocks,etc. Geologists gather measurements and observations from strain markers. This information can be used to develop a strain ellipsoid.
The purpose of a strain ellipsoid is to describe the strain caused by a deformational event in three dimensions. It compares the change from a pre-deformation sphere where X=Y=Z to a post-deformation ellipsoid where X>Y>Z. The following diagram shows a sphere and the three types of strain ellipsoids.
Deformation of any structure can be described with strain ellipsoids. Descriptions of strain are ultimately used to describe and examine stresses which are the forces that produce strain. The study of strain and stress is addressed in extremely large structural geology textbooks. We've covered the basic ideas that I use in blacksmithing.
Many of the forms in my work have developed through the process of creating strain markers in metal and finding ways to deform (stress) these structures to reveal the beautiful, plastic nature of metal. I've created strain markers by cutting, forging, twisting, drilling, punching, bending, and scoring. I often use more than one of these techniques in creating a single strain marker or group of strain markers.
There are three basic ways that a blacksmith applies stresses to hot metal: bending, twisting, and forging (hammering or squeezing). Stretching is another possibility that I have explored through bending, twisting, and forging but it can be accomplished in more direct ways. I believe that stretching has extensive possibilities based on my experience and because many beautiful forms and textures are created by stretching in natural growth. There are also many beautiful stretched geologic, hydraulic, atmospheric, planetary, and galactic forms. Metal can be reheated and reworked multiple times so there are an infinite number of possibilities in creating strain sequences in metal.
I've tried many different approaches in applying strain analysis to blacksmithing. However, the creative process is not a linear one for me. It evolves through experiments, mistakes, incessant cogitation, luck, etc. I use strain analysis and its relevance to the strain markers and stresses I can produce in a blacksmith's shop as tools, but it is only through the craft of blacksmithing that I can make the metal beautiful. It seems to me that my work has a lot in common with Damascus steel (the layered, wavy steel often seen in knives) although I have no experience with Damascus. My understanding is that Damascus is produced by deforming different kinds of steel together, while I use one kind of steel and space.
There are many examples of blacksmiths finding beauty by deforming shapes. Strain analysis is useful in my work and I believe that other smiths will find it useful too.