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Reviews > Cook Gear > Stoves > Primus EtaExpress > Test Report by Rick Dreher

PRIMUS ETAEXPRESS INTEGRATED STOVE SYSTEM
TEST SERIES BY RICK DREHER
LONG-TERM REPORT
August 24, 2008

CLICK HERE TO SKIP TO THE FIELD REPORT
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TESTER INFORMATION

NAME: Rick Dreher
EMAIL: redbike64(at)hotmail(dot)com
AGE: 54
LOCATION: Northern California
GENDER: M
HEIGHT: 6' 0" (2.10 m)
WEIGHT: 175 lb (79.40 kg)
TORSO LENGTH 20 inches (50 cm)
YEARS HIKING 41

I enjoy going high and light and most often take shorter "fast- packing" trips; my longest trips are about a week. I've lightened my pack load because I enjoy hiking more when toting less, I can go farther and on tougher terrain, and I have cranky ankles. I use trekking poles and generally hike solo or tandem. I've backpacked all over the west and now primarily hike California's Sierra Nevada. My favorite trips are alpine and include off-trail travel and sleeping in high places. When winter arrives, I head back for snowshoe outings in the white stuff.


INITIAL REPORT

PRODUCT INFORMATION & SPECIFICATIONS

IMAGE 1


Manufacturer: Primus
Year of Manufacture: 2008
Manufacturer's Website: Primus Sweden
MSRP: US$90.00
Listed Weight: 14.7 oz (418 g)
Measured Weight (incl. stuffsacks): 15.2 oz (431 g)
Measured Burner Weight: 3.2 ounces (91 g)
Measured Pot Weight: 7.2 ounces (204 g)
Measured Lid Weight: 2.6 ounces (74 g)
Measured Windscreen Weight: 1.4 ounces (40 g)
Measured Stuffsacks Weight: 0.6 ounce (17 g)
Measured Pot Width/Height (excl. heat-exchanger): 4.5 inches (11.5 cm) x 4.375 (11.2 cm)
Measured Lid Width/Height: 4.5 inches (11.5 cm) x 1.25 inches (2.8 cm)
Listed/Measured Capacity: 1L (38 fl. oz.)

INITIAL IMPRESSIONS

The EtaExpress comprises a canister-top isobutane-propane gas stove, a cookpot with heat-exchanger bottom, a pot lid/frypan, a rigid windscreen and stuffsacks. The design, notes Primus, is intended to supply high fuel efficiency in a small and "extremely low total weight" package.

IMAGE 2
EtaExpress System--Complete



The Unboxing

EtaExpress comes boxed complete, sans fuel. The stove and windscreen fit easily inside the pot and lid with room left over for a canister. Two stuffsacks are provided: one for the whole works and one for the little stove burner. There's an instruction sheet for the burner, which also has a safe use hangtag.

The stove burner appears fashioned entirely from brass and steel, other than the plastic knob and a plastic bit around the piezo assembly.

The pot, lid and windscreen are fashioned of spun aluminum, anodized gray. The pot and lid are lined with what Primus calls "triple layer Titanium non-stick" coating. It looks and feels like Teflon-type ptfe* to me. Pot and lid have foldaway, rubber-insulated steel wire handles. The lid's single handle locks open or closed; the two pot handles swing open and closed freely. The lid doubles as a minuscule frypan, and its rolled lip sits inside the pot's contoured lip for a reasonably snug fit. The pot has a very small pour spout. Pot, lid and windscreen all seem sturdy; my impression is they're made of thicker aluminum than some backpacking cookware, and are considerably thicker than the titanium pots I own.

Up to now I'm describing an ordinary pot set. However, on the pot bottom is what makes it part of the Eta system: a heat-exchanger ring. This is a circle of continuous aluminum fins welded to the pot bottom and protected by a facing welded ring. Primus documentation doesn't describe the ring's function, but it's easy to conclude it functions as a sort of reverse radiator, capturing and directing what would otherwise be waste stove heat into the pot, increasing heat transfer to breakfast or dinner. The heat exchanger's actual welded surface area can't be very great, however.

IMAGE 3
Eta Heat-Exchanger



The windscreen is rigid aluminum formed into a nearly half-cylinder that's open on top and closed on the bottom. Keyhole slots in the side are for poking two of the three stove pot supports through, for support. Below those are airflow slots to supply burner air. The windscreen fits on the opposite side from the fuel valve and sits atop the piezo switch. It wraps a third or more of the way around the Eta pot and about halfway up the side. Clearly, the stove must be rotated to keep this partial screen facing the wind, as the other side remains completely open.

As noted and in keeping with the EtaExpress' mission to provide a very compact cook system, the works fit inside the pot along with a small or medium fuel canister. Primus thoughtfully supplied a cloth to keep the system bits and a canister from grinding off the non-stick coating. The burner has its own nylon stuffsack and the whole works has a large, mesh stuffsack.

* ptfe = polytetrafluoroethene, a common form of Teflon-type fluoropolymers.

READING THE INSTRUCTIONS

Thorough stove burner instructions are also provided but, surprisingly, there are no EtaExpress system instructions or even usage pointers, other than what few tidbits can be gleaned from the box. The Primus, Sweden Web site has an Eta system video that doesn't address the Express at all. A large and stiff stove safety label dangles annoyingly from the control valve shaft, rather like an oversize mattress warning tag. It will need to be removed. The paper stove instructions cover (by my count) eleven languages, making this quite the international product. So international is the EtaExpress it's made in Estonia, the only such item I've ever seen.

IMAGE 4
Assembled, ready to cook.


TRYING IT OUT

The Express model 3214 stove (isobutane-propane burner) is very compact and relatively light. Its three pot supports swing around the vertical axis to open at 120-degree angles to one another, and swing back together for storage. A single plastic control knob juts out from the stove base and on the other side is the piezo igniter switch. The flat burner head aims the flame directly upwards, not to the sides as with many compact stoves. This design makes a tall, skinny flame rather than a broad one.

IMAGE 5
Tall, hot flame.



Setup and Lighting

The instructions only cover operating the burner, as follows: Spin the burner onto a Lindal-valve fuel cartridge. Open the pot supports (one of the supports is fixed, one swings open and locks into position and one swings open to a stop but doesn't lock). Next, but not covered by the instructions, place the windscreen onto the two pot supports opposite the valve. Then open the fuel valve and pull the igniter switch to light. Adjust the flame as required. Place the pot and lid. Note: the pot doesn't lock onto the stove.

To hang the stove using a Primus accessory kit, the cables must be connected to the pot supports.

Despite the photo on the Primus box, the lid is intended to be used inverted on the pot; otherwise, a tight seal can't be had. Even then, the handle must be unlocked and swing upward a bit to ensure the fit. Face-up, the lid/pan doesn't fit snugly because the handle base itself interferes with a good fit and could scratch the pot's finish. It might, however, occasionally be used this way to keep food stored in the pan warm while cooking continues in the main pot.

IMAGE 6
Lid handle base interferes with fit.

TESTING STRATEGY

I'll perform time-to-boil tests using the system pot and a second, non-system comparison pot. I'll also measure fuel consumed by weight. I'll also note any difficulties lighting the stove using the piezo igniter. Then, I'll figure out a scheme for cooking with the relatively tall, narrow pot and tiny frypan and go hiking. Over the course of the test, I'll consider the system's flexibility, ease of use, fuel efficiency and resistance to normal wear and tear.

Unless there's trick I've not figured out, some modification might be needed to the lid handle anchor so it doesn't interfere with the pot lip and provides a good fit whether inverted or face-up. This will have a positive effect on Primus' stated goal of high efficiency for the EtaExpress, and I'll fiddle with the fit as part of my testing.

SUMMARY

Compact and complete, the Primus EtaExpress system appears to be a well-made, clever cooking system. It would be possible to assemble the equivalent system bits for less money and weight so the question arises, does the heat-exchanger technology provide sufficient efficiency and speed to warrant the extra cost and mass?


FIELD REPORT

Field Locations and Conditions

I took the EtaExpress on three backpacking trips: two one-night trips in Desolation Wilderness and one two-nighter in Lassen National Park. The Desolation solo trips were between 6,500 and 7,500 feet (2,000-2,300 m), with mild weather for one (60 F/15 C) and cold (45 F/7 C) and rainy for the other. The Lassen group trip was at 6,500 feet (2,000 m) and brought mild temperatures (60-70 F/ 15-21 C) with pleasant weather on days one and three, and intermittently stormy weather with wind, rain and hail on day two.

IMAGE 7
EtaExpress in hammockland.

Field Performance

Most of my stove use was heating water for reconstituting food and for hot drinks, although I also made rice in the pot. A wooden paddle/spatula provides safe stirring, scraping and serving without damaging the nonstick coating. I've also melted snow for drinking and cooking water, and the system made quick work of soggy springtime snow. Stove setup and operation were quite simple and quick in all conditions. Because it's relatively tall atop the cartridge, canister footing needs to be level and stable or the stove rocks, although I'm not above plopping it on the soggy ground and firing it up when I want hot water, "stat!" Lighting via the piezo igniter is trickier at altitude and in cold weather than at sea level in shirtsleeve weather, but it does still work with careful control of the fuel flow (too much fuel and it won't light). The partial-coverage windscreen is at a perfect height to protect pot and flame while retaining access to the valve and igniter, but it still leaves the flame vulnerable to wind so a sheltered spot is needed in poor weather.

IMAGE 8
Handy snow=handy water.



In the field the stove heats fast, melting snow and boiling water quickly. It seems frugal, because a standard 220g (7.8 oz) cartridge lasts multiple days, although I don't yet have a good idea of how many cartridges to budget for longer, multi-person trips. As with all vapor-feed canister stoves, the Express flame becomes feeble with nearly spent cartridges. Warming the cartridge helps wring out the last bit of fuel.

The pot's tiny pourspout doesn't seem effective in directing a stream of hot water into a food container or cup, and so far I've not used the minuscule frypan lid for anything other than a lid.

Packing

The EtaExpress makes a tidy package, with a standard canister stowed inside the pot, along with the burner and windscreen. To avoid damaging the heat-exchanger fins, I try to pad it inside the pack using clothes, etc. It has to go inside the pack, as my pack pockets aren't large enough to stow it there.

Wear and Tear

The EtaExpress system remains in good condition. The pot has accumulated a couple minor dents and some fins have been flattened (and straightened), the burner is heat-discolored, but everything else is as new. Importantly, the nonstick coating is intact.

IMAGE 9
EtaExpress boils fast enough for me.

Bench Testing

In an attempt to baseline the EtaExpress fuel consumption and determine the impact of the heat-exchanger pot and windscreen, I ran some water boil tests using three options. My test conditions were as follows:

Water volume: 500 ml (17 fl oz)
Water temperature: 66 F (19 C)
Air temperature: 90 F (31 C)
Elevation: sea level
Wind:
New 220g (7.8 oz) cartridge

IMAGE 10
Time for scrutiny.



I tested 1. the complete EtaExpress kit, 2. the Eta pot without the windscreen, and 3. another pot--a slightly smaller titanium kettle of roughly the same height/width ratio--with the Eta windscreen. I hoped to discover the effect the individual Eta components--pot and windscreen--have on efficiency by removing them from the system individually. I measured the time to boil for each combination, using an immersed thermometer probe to stop when the water reached boiling temperature, then weighed the canister to determine fuel use. Unfortunately, I wasn't able to pry any significant difference among the three modes. Either environmental variables overwhelmed the system differences, my scale isn't accurate enough to tease out small (fuel) weight measurements, or there's no significant difference. Time to boil was similar for all three variations, but since it's not possible to exactly match the valve setting between tests I don't put much value on boil times. In all cases I used a moderate flame to maximize efficiency. The Express burner will crank out a really big flame, if desired, although it wastefully wraps up the pot sides.

My tinkering wasn't for nothing, because I can at least note that EtaExpress averaged 0.5 oz (13 g) fuel per liter boiled (with a 66 F [18 C] starting temperature). I infere this to mean a 220g (7.8 oz) standard cartridge might yield 17 liters of boiling water under the same conditions.

IMAGE 11
Different pot, same result.



Manufacturing Changes

I've checked out two or three EtaExpress systems in the store to see whether there have been any changes from my tester. I discovered the pot and/or lid has been altered and now the lid fits snugly without partly folding the lid handle. The heat-exchanger fins are now reinforced by a metal ring circling the inside to about half-height. This should prevent their being crushed completely flat against the pot bottom by accident, a possibility--however remote--with the pot I'm testing. I view both changes as distinct improvements.

Summary

The EtaExpress is a slick, easy-to-pack and easy-to-use system. The stove burner folds small, is fairly light and performs well (lights easily, easy to control). The windscreen solves the thorny problem of how to get the windscreen up by the burner while leaving access to the igniter and valve, especially versus the foil screens I usually fiddle with on canister-top stoves. The pot is a reasonable size for one or two, and has the added heat-exchanger feature.

My controlled tests didn't demonstrate much of an efficiency impact from the heat-exchanger pot or windscreen. There may indeed be a difference using them, but my little experiments didn't reveal any.

Based on my "investigative shopping," Primus has already addressed a couple of issues by altering the lid fit and reinforcing the pot fins. My sole question at present is whether they'd gain better performance by increasing how far the windscreen wraps around the pot, perhaps halfway or even two-thirds. It would definitely enhance wind protection, perhaps efficiency as well?

Testing Strategy

I'll continue to use EtaExpress the rest of the summer, likely as not extending my cooking experiments beyond what I've done so far. Watch for the long-term report in two months.


LONG-TERM REPORT

Long-Term Test Locations and Conditions

IMAGE 12
Kitchen with a view.



I took the EtaExpress on three more trips: one-night and two-night solo hikes in Desolation Wilderness and a two-night two-person hike in Emigrant Wilderness. I used the system exclusively, taking no auxiliary pot (although I took a cup, bowl and flatware). All three trips were in warm and mild summer conditions, and my mealtime temperatures ranged from a low of about 42 F (7 C) in the morning and a high of about 75 F (25 C) in the evening. In addition, I often left the canister in the sun in the afternoon, heating the contents and enhancing fuel pressure. Winds ranged from dead calm to moderately breezy, never strong (although wind direction was often fickle, quickly changing). In most cases I was able to set up the stove in a sheltered, level spot. Sometimes this would be in soil and other times on rocks or rock slab.

My campsite elevations ranged from about 7,000 feet (2,130 m) to 8,500 feet (2,590 m).

Field Performance

Setup. As noted previously, the all-in-one kit with fuel stored in the pot assures I have everything in hand every time. Assembly and setup takes perhaps a minute (except when I get the canister stuck inside the pot). Setting the EtaExpress up on soil, I can level the canister base pretty solidly, although soft, loose soil can render the stove tippy with a full pot on top, and require a firmer base. Stably leveling the stove on rock is trickier, sometimes requiring sticks or pebbles to keep it level and prevent rocking. Note: all my trips were with "standard" 220 g cartridges, and I never used the EtaExpress in the field on the narrower 110 g small cartridges. After trying it on a small cartridge at home I decided the stove, windscreen and full pot are too top-heavy to be safely used on one.

Lighting. The peizo igniter remained touchy throughout, although I made it through the field test portion without resorting to a lighter. My tips are to warm the canister, shelter the stove from the slightest breeze, turn on the gas as low as possible, and keep clicking until it lights. Eventually, it does. In very cold weather or strong wind, a lighter is much faster, although there's the possibility of a knuckle-singeing flare-up (as my home tests amply demonstrated). The windscreen's approximately one-third coverage is inadequate for breezy weather, and the stove requires additional shelter to light and operate predictably. I used rock, wood, gear--whatever I could adapt as additional windscreen where I'd set up my kitchen. Adequately sheltered, the stove never faltered in use.

IMAGE 13
Baby FryBaby.



Cooking and Cleaning. The EtaExpress turns out to be a nice-and-easy cooking rig. I made quite a few "real" meals on it, as well as boiling a lot of water for reconstitute-and-eat meals, instant cereal, coffee, etc. I sautéed ingredients in the pot and in the mini-frypan lid, kept them warm in the inverted lid atop the pot while preparing the rest of the dish, then combining everything and using the pot as a dish.

In nearly all situations I used a very low flame, which the Express burner was always able to maintain, with no relighting or fiddling with the valve. The aluminum pot and lid transmit heat very fast and water boils fast, ingredients in oil brown quickly and food simmers at a very low setting. To its credit, between the controllable burner and non-stick pot coating I never burned anything during the test.

Sautéing in the lid makes it easy to add and stir ingredients, but it's also easy to spill them when shaking the pan. The much deeper pot keeps everything inside no matter how much I shake or tip it, which makes it a bit easier and safer. I'm satisfied either option work fine, despite the lid's minuscule dimensions. I've previously noted the lid's refusal to sit flat on the pot without partially folding the handle, and this continued to annoy me throughout the test, although I worked around it. Hot ingredients remained hot in the inverted lid atop the pot while heating water/cooking other ingredients, so providing the little pan instead of a flat lid seems like a valid design decision. A flat foil lid can be easily substituted.

IMAGE 14
Keeping it warm while boiling water. Ant says, "Hurry up."



My favorite two meals of this test were smoked salmon and mashed potatoes, and lamb and rice. Noodle dishes worked okay too, but I don't like the boil-and-drain routine without a second pot handy. As a main course in a multi-course meal, the EtaExpress pot capacity is enough for two. As a lone course dinner for me, it's almost too much food.

Evening cleanup proved simple, as the non-stick coating did its job. I wash it with water and a little Camp Suds using a scrubber sponge, rinse it well and set it up for the morning. There's always a patina of grease that I don't get off until back home, but not enough to ruin the morning coffee.

Morning hot water for coffee and cereal couldn't be simpler. I fill it in the evening and set it away, safe from my large and clumsy feet where I can spark it up in the morning and have hot food and drink in my cup and bowl in a few minutes. Once they're empty, I wipe the pot and lid dry and pack away the entire works in a minute or two.

Fuel Consumption: I averaged about an ounce (28 g) of fuel per day traveling solo. A standard 220 g (7.76 oz) cartridge should comfortably last for a week, presuming mild weather and the ability to wring out all the canister's contents. I didn't have enough two-person nights to yield a reliable average, but observed fuel used per person per day was less than double the solo consumption rate, presumably due to not cooking separate meals.

Summary

The EtaExpress system is slick and simple. It's relatively compact and, while I can't call it light it also isn't heavy. This test has convinced me that with a little menu matching to its capacity and dimensions, it can support the single hiker and a pair of hikers through an array of interesting meals, far beyond merely boiling water to heat up dehydrated packaged meals.

IMAGE 15
The final mashup.



The EtaExpress's strengths are compactness, completeness and ease of use. It has proven well made, as mine remains in near-new condition, with a few minor dings in the pot and a couple of flattened fins in the heat-exchanger. The non-stick coating is fine. It seems frugal with respect to fuel use and the flame control is very good, even if the flame pattern is a narrow spot rather than wide-spread.

EtaExpress weaknesses are the spotty igniter, the lid's poor fit and the windscreen's minimal coverage.

I've not been able to verify or refute any efficiency gains from the windscreen and heat exchanger, so I'm neutral on them. The system is neither particularly light nor heavy for its capacity and performance, instead sitting in the vast mid-pack.

My suggestions for Primus are to consider reevaluating whether the Express burner should be the basis for this system, or if they should base it on a lighter burner with a wider flame pattern and more dependable igniter (I own a Primus titanium burner that could be a strong contender). I'd also consider a way to connect the pot to the burner to make it a rigid system and wrapping the windscreen farther around the pot. Finally, the lid needs to fit snugly, for both safety and efficiency purposes.

Continued Use

The EtaExpress is so easy and relatively compact I'll likely grab it for shorter backpacking trips and even wintertime day trips when I want hot food and drinks. I'll continue to take it on family outings for the same reasons.

As trips get longer, the hiking party becomes larger, or winter looms, I'll leave it at home. I can assemble its equivalent for half the weight or less from my gear vault, and that becomes critical in keeping pack weight and bulk down. The pot's too small and limited for cooking for more than two, or serious snow-melting for water (not to mention Primus has other Eta stoves they recommend for winter). These aren't indictments; rather, there're simply practical limits of the system as designed.

Acknowledgements

I thank Primus and BackpackGearTest for the chance to test the EtaExpress!

This report was created with the BackpackGearTest.org Report Writer Version 1. Copyright 2008. All rights reserved.

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