Sivetz Roasting Machines
Production drums, Corvallis, then Hood River, Oregon, United States.
History
Michael Sivetz (1922-2012) was a chemical engineer. In 2004 he claimed more than forty years of industrial coffee experience, in the United States and elsewhere. He advised instant coffee plants and designed their processes. Hence his grievance against large production drums, which he knew from the inside. A fluidized bed is a heap of beans lifted by a rising current of air, which then begins to flow like a liquid. On November 11, 1974, from his home in Corvallis, Oregon, he filed the patent that would become US 3,964,175. The company says it was founded that year. In 1980 he converted a former Corvallis church into a laboratory, showroom and workshop. More than three hundred machines would come out of it over thirty years, according to the company. A single Corvallis machine shop is said to have built them all, according to its owner, interviewed in 2017. Sivetz also wrote, and that is perhaps where he carries the most weight. Coffee Processing Technology appeared in 1963, 736 pages, reworked in 1979 under the title Coffee Technology. The book armed a generation of roasters against the pitch of the big industrial makers of canned ground coffee. He died in 2012. Ten years passed before the brand reappeared. In 2022 Michael Barthmus, founder of Doppio Coffee in Hood River, bought it from Sivetz's son-in-law. A partner accompanied him at the start, then the two men parted amicably. Fifteen months of work produced the SRM15, unveiled at the Specialty Coffee Expo in Boston in April 2022. The headquarters and showroom opened in Hood River in December 2024. In April 2026 the company merged its activities with Peachey Roasters, of Kansas, to bring electric heating back. Corwin Peachey runs this range from Kansas, near Wichita.
What it makes
Fluidized-bed roasters. The 1974 patent lays down the principle. The beans are levitated in a chamber by a rising current of air. They form a dense mass that recirculates on itself. Heat passes first by convection, through the air that surrounds each bean, and only afterward by conduction from bean to bean. The patent caps the inlet air at 530 degrees Fahrenheit, or 277 degrees Celsius. This is the opposite of the production drum, where a hot metal wall cooks the bean by contact. There is therefore no drum, no scorching wall, no rotating part in the chamber: only the air moves. The company sums it up by saying the machine has only one moving part, the turbine. The air passes through the bed only once, Sivetz wrote in 2002, instead of being sent back in a loop. The chaff, that thin skin that comes off the bean during roasting, therefore goes straight to a stainless steel cyclone, without time to scorch. Cooling takes place in a separate tray, which frees the chamber as soon as the batch is dropped. The SRM15 is gas-heated, with a Midco RE4400DS burner and a Maxitrol modulating valve. The SRM5E and SRM9E are heated by electricity, and so without combustion on site. The machines from before 2022 did cut the heat off by themselves at the target bean temperature, but could not be adjusted during roasting. The SRM15 adds continuous control of the fan and the gas. A PID controller, a loop that continuously corrects the deviation from the setpoint, holds the temperature of the incoming air. The electric models carry four 2 mm thermocouples and three operating modes. The gas machines are assembled in Oregon, the electric ones in Kansas since 2026.
The models
Catalog consulted in September 2026. SRM15, gas, whose figures diverge by source. The manufacturer's technical sheet, dated February 2024, gives 9 to 17 kg per batch. It announces 6 to 11 minutes of roasting and 60 to 90 kg of green coffee per hour. The manufacturer's website announces at the same time 4 to 15 kg per batch, 7 to 9 minutes and up to 90 kg per hour. Burner of 400,000 BTU per hour, natural gas between 7 and 14 inches of water column. Motors at 208 to 240 volts, 30 amps single-phase: 3 horsepower fan with variable-speed drive, 1 horsepower cooling, optional 1/4 horsepower motorized agitator arm. Water supply at 50 psi minimum. Weight 700 kg, footprint 3,556 by 1,880 mm, chaff cyclone 2,718 mm high. Announced price 54,500 dollars in 2022, lead time six months. SRM5E, electric: 1 to 5 kg per batch, 8 to 10 minutes, up to 30 kg of green per hour. It draws 220 to 240 volts at 75 amps single-phase, 16.8 kW at peak, and weighs 158 kg. SRM9E, electric: 2 to 9 kg, 8 to 10 minutes, up to 45 kg per hour. It draws 220 to 240 volts at 120 amps single-phase, 26.4 kW at peak, and weighs 204 kg. Both exhaust at 371 degrees Celsius at peak and require a duct of at least 102 mm. Twenty programmable recipes on the touchscreen. An SRM35 has been announced since December 2024 and was still listed as in development in April 2026. Michael Sivetz's range went from 30 grams to 70 kg per batch, according to his own website in 2004.
What you gain
Convection surrounds every face of the bean at once. No metal wall touches it, so no contact burns and no blackened tips. The patent caps the incoming air at 277 degrees Celsius, far below the sheet metal of a direct-flame drum. Since the cooling tray is separate from the chamber, the next batch starts right away. Hence the short cycles, 6 to 11 minutes on the SRM15, up to 90 kg of green per hour. Since the air passes only once, the chaff goes off to the cyclone and does not burn in the chamber. The bean bathes in air instead of rolling against a wall. A thermocouple planted in the bed therefore truly gives its temperature. This is what already allowed the old machines to cut the heat exactly at the desired roast degree. Only one part turns, the turbine, and nothing scrapes the chamber: maintenance benefits.
What you lose
The air fluidizes the bed and carries the heat in the same movement. The two levers remain linked: stirring cannot be changed without touching the heat input. Until 2022, moreover, there was no adjustment during roasting at all, only a cutoff when the temperature threshold was reached. A fluidized-bed profile cannot be transposed to a drum, nor the reverse. Since the air is used only once, its heat leaves through the duct: the electric models exhaust up to 371 degrees Celsius at peak. A duct that withstands this temperature is therefore needed, 102 mm in diameter at minimum. The installation is heavy. It takes 120 amps single-phase for the SRM9E, 400,000 BTU per hour for the SRM15. It also takes a water supply and a cyclone 2.7 meters high. And the deliverable catalog stops at 15 kg.