Sid Hammer first started experimenting with etching polyvinyl-chloride (PVC) sheets with hot tools in the early 1950s. He discovered that this technique allowed him a creative freedom and appearance not possible with other conventional etching techniques.

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Hammer explains the benefits of thermo-intaglio in an article entitled “A New Intaglio Technique,” (February 1963, American Artist). PVC plates are more affordable than either copper or zinc and the material is softer, which when paired with differently shaped heated metal tips of a modified soldering iron, allowed him to etch plates with a painterly, freehand approach. The resulting print plates produce extremely dark blacks, due to the depth of the lines and burrs achieved as the hot point of the soldering iron tools melt the surface of the plate. The plates are also more durable than drypoint engravings, allowing Hammer to make larger editions before the plates degraded. Unlike metal-plate etching techniques, thermo-intaglio allowed him to easily make repeated revisions to plates without the need to chemically clean the plates, further adding to the free-form nature and speed this technique afforded him while going through the proofing and revision process. Hammer liked the “directness of these plates as an expression of the artist’s intention.”

 

In addition to the novel hot-tool etching technique that differentiates thermo-intaglio from other engraving and etching processes, Hammer also utilized conventional drypoint, graven line, mezzotint, and other techniques as he saw fit throughout the process of making and proofing his plates. Later prints included areas where he applied homemade black gunpowder to sections of the plate, which when lit melted the surface, creating interesting and varied graytones.

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