Herbert Arnold Zenit Glass Torch

The Herbert Arnold Zenit is a single-stage surface-mix bench burner built around a concentric-ring head rather than the stacked, independently controlled stages you see on many boro torches. A single twist grip carries it from a needle point to a large, bushy flame, and its reputation is a quiet, even flame, credited to a flame-stabilizing system, the trait that has made the Zenit a favorite for precise scientific glasswork. It comes from Herbert Arnold, the German glass-machinery maker in Weilburg, at the premium European end of the craft.

What the surface-mix flame gives you

Like other surface-mix burners, the Zenit mixes fuel and oxygen at the face of the torch rather than inside the body; Arnold’s catalog calls it a separate-gas system (Getrenntgassystem). That keeps the mixing chamber cool and gives a clean, controllable flame. The propane and natural-gas versions add a third input, compressed air at 0.5 to 1 bar, which is how the burner runs a cooler, calmer flame without starving the fire. For the broader background on how surface mix differs from premix, see surface mix vs premix torches; for Arnold’s particular concentric-ring approach, see Herbert Arnold concentric-ring burners.

Who the Zenit is for

Arnold rates the Zenit for borosilicate, and the hydrogen version for quartz as well, so it suits scientific, technical and production boro work where a quiet, controllable, repeatable flame matters; the head size you choose sets how large the work can go. Arnold’s data sheets name no soft glass for it. In practice the choice narrows to two heads: In Joe Blanchard’s sixteen years on the distribution side of the glass industry, the Zenits people bought and ran were the 40 mm, rated for tubing up to about 80 mm, and the 65 mm, for work over 100 mm. The 50 mm is on Arnold’s list, but it is rarely the one on a bench. It’s an intermediate-to-advanced burner rather than a first torch, and most beginners start cheaper. If you’re weighing it against other options, our how to choose a glass torch guide walks through the trade-offs.

Versions, pressures and list prices

Arnold builds the Zenit as three separate burners by fuel: 114/1 PSL for propane, 114/2 ESL for natural gas and 114/3 WS for hydrogen, each in 40, 50 and 65 mm heads. A given burner runs the fuel it was built for. Every figure below is from Arnold’s burner catalog (page 24) and its 02/2025 price list, read on 2026-10-06; prices are in euros, excluding VAT.

In PSI, the fuel pressures are low: 50 mbar is about 0.7 psi and 22 mbar about 0.3 psi, while hydrogen runs 500 mbar (about 7 psi) or 1,000 mbar (about 14.5 psi) on the big head. Oxygen runs 1.5 to 2.8 bar, about 22 to 41 psi (our conversions). Two details to settle with Arnold before you order:

• The 65 mm oxygen setting. The catalog gives 2.8 bar; the separate Zenit brochure gives 3.5 bar (about 51 psi). Both are Arnold’s figures.
• The head suffix. The price list also carries N-M7 versions of the 40 and 50 mm heads at lower prices (EUR 2,645 and 2,414 for the 40 mm propane and natural-gas heads, for example). The catalog says the standard M7 head has no gas fine-adjustment screw and an optional head adds one, but it never says which suffix is which, so ask.

On the hydrogen version, Arnold rates the three heads for quartz tubing of about 50, 60 and 80 mm.

Oxygen and fuel demand

Arnold publishes maximum consumption for every version, which most makers do not. The 40 mm propane head draws at most 0.5 cubic meters of propane and 3.5 of oxygen an hour, about 58 LPM of oxygen, which is the figure on this page. The heads climb from there: the 65 mm natural-gas head tops out at 8.0 m3/h of oxygen and the 65 mm hydrogen head at 8.8 (about 133 and 147 LPM). Those are ceilings at the largest flame, not what a working flame draws, but they tell you a big Zenit head is a bulk-oxygen or tank burner, not a concentrator one. See how many LPM does my torch need and oxygen concentrator vs tanks.

Dialing the flame

Where multi-valve boro torches ask you to balance several fires, the Zenit keeps it simple: ball valves and a single twist grip that Arnold says changes the flame continuously, from a needle point up to an intensive, bushy flame. That makes for a forgiving, predictable burner once you’ve learned its range, part of why it earns its place in scientific labs and quiet studios. It sits on a heavy cast-iron base with a ball joint, and the burner weighs 6.9 to 10.4 kg depending on head and fuel.

Before you buy

Budget for the whole system, not just the torch: oxygen (tanks or bulk for the larger heads), a regulator for your fuel, flashback protection matched to your torch and gas supply, eyewear selected for the glass and process, with quartz-specific protection when working quartz, and ventilation. Arnold recommends protection against reverse gas flow and flashback and sells regulators, a safety-screen holder, a table clamp and a US adapter set that converts the gas, air and oxygen connections to 9/16-inch fittings. Its terms limit defect claims to 12 months, and it offers an on-site service visit for the Zenit (jets checked, air taps greased, burner adjusted) at a fixed inspection price. New to plumbing a torch? Start with the fittings, hoses & connectors guide and the glass torch safety setup guide.

Editor’s note: versions, pressures, consumption, weights and euro prices come from Herbert Arnold’s burner catalog, Zenit brochure and 02/2025 price list, as read on 2026-10-06; where the catalog and brochure disagree we show both. The quiet-flame reputation and the flame-stabilizer description come from earlier reads of Arnold’s materials and listings, not from these data sheets. Confirm the exact head, fuel, operating range and current price with Herbert Arnold.