The Art of Sandblasting

Sandblasting is the process of propelling fine abrasive particles at a surface with compressed air or suction. In pipe making it's known not to be a simple finishing step: two stummels from the same workshop can look wildly different depending on the machine used, the type of abrasive, the wood's grain, and the habits of the hand at the bench.

From Industry to the Pipe Bench

The method wasn't invented for pipes. Benjamin Chew Tilghman registered sandblasting in the United States on 18 October 1870 under patent No. 108,408; the document covered cutting and etching stone, metal, and glass, with wood not yet on the agenda. He is said to have hit on the idea after watching desert wind-blown sand frost glass surfaces — a story that itself appears in sources with a caveat of legend. Real industrial uptake came only after compressed air was added to the setup in 1904.

Bringing the technique to the pipe took another generation. Dunhill had moved pipe production to its facility at Notting Hill Gate in London in 1916. The first filing for the British patent on the Shell Briar finish (No. 1484/17) was submitted 13 October 1917, completed 12 April 1918, and granted on 14 October of that same year; the American patent followed in 1920, the Canadian in 1921. Documentation of the finish's earliest years consists largely of this patent record; sandblasted pipes are absent from period catalogs and advertisements.

Abrasive and Machine

The first factor shaping the surface is what grain meets the wood. Silica sand, garnet, glass beads, steel shot, crushed steel, walnut shell, and crushed fruit pits are all common abrasives; each leaves a different depth and texture, and a material that gives the right result in one workshop may not meet expectations in another. Silica sand has been banned in the United Kingdom, Germany, Belgium, Sweden, and Russia because of the risk of silicosis.

On the machine side there are two basic setups. In suction (vacuum) cabinets, particles are drawn to the nozzle by suction not exceeding one atmosphere; most small workshop machines work this way. In pressure-pot machines, the abrasive is fed from a sealed vessel under compressed air, the flow is far more forceful, and the pressure can be raised as far as the compressor and plumbing allow — deep relief requires exactly this.

How the hand engages also shows in the result. In cabinets with a fixed nozzle, the maker turns the stummel with both hands and switches the flow on and off with a foot pedal; in gun-style setups, one hand holds the stummel while the other directs the nozzle. In automated setups, a large batch of stummels is tumbled for hours in a wire drum while a fixed nozzle blasts at low pressure. Because the pieces rub against each other in the drum, edges round off and the texture softens; a sandblast with sharp, distinct edges is therefore taken to have been worked by hand.

Grain, Curing, and Depth

The depth of the relief depends largely on the briar block itself. Curing's effect on this is disputed: makers don't agree on which of air-drying, kiln-drying, oil curing, steaming, or soaking in water improves a sandblast; some argue their own method makes a clear difference, others report seeing no difference at all in their own trials. Ashton's practice of steaming a cured bowl to raise the soft grain before blasting is one known example of this search.

The direction of the grain also shows up in the pattern. It's reported that until the early 1960s sawmills cut without regard for grain, leaving plenty of cross- and mixed-grain blocks in circulation — blocks said to give more intricate blast patterns. As Italian and Danish makers gained influence, cutting shifted toward straight grain, which in turn brought out ring patterns more prominently on sandblasted surfaces.

Flaw or Preference

It's a common misconception that a sandblasted pipe was made from a flawed stummel. Until the 1930s, smooth pipes were mostly stained in shades of burgundy or dark walnut, so small sand marks stayed hidden under the stain. The spread of light natural finishes made these marks visible and pushed sandblasting into wider use. Shedding excess weight from the stummel, or hiding a stain that couldn't be applied evenly on a smooth surface, are also cited among the reasons for the choice. For a comparison with other finishes, see surface finishes.