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Reviews > Cook Gear > Stoves > Primus AB ETA Solo Stove > Test Report by Ben Mansfield
Primus Eta Solo Stove
Primus Eta Solo Stove
23 July 2010
* Note: The manufacturer's website doesn't specify how much or little of the stove is included in this figure. In my detailed breakdown of the weights of the components (below), the picture will hopefully be a little clearer.
The Primus Eta Solo Stove
The Primus Eta Solo stove is a self-contained backpacking stove and pot system designed to be compact, light, and efficient. It features a burner element which screws directly onto the fuel canister. The pot portion of the stove is a 0.9 L (30 oz) cup with an attached heat exchanger. The pot clips into the stove for security and a tight fit for the heat exchanger. The system also includes pot supports and a heat reflector shield which allow the Eta Solo to be used with a third-party pot or cup. There's a foldable plastic tripod that holds the fuel canister securely to help prevent the whole system from tipping, but the stove also includes an attachment to hang the stove and pot, allowing the stove to be operated without resting on the ground.
The pot itself is simple enough, and the kit includes an insulating wrap that goes around the pot and attaches to itself with a hook-and-loop closure with a sewn-in webbing handle, making it rather like a cup or mug. There's also a rubber lid that snaps onto the pot with an opening for drinking and a small hole in the center, I assume as an air vent. A small tube is attached near the top of the pot, which is the attachment mechanism for the hanger apparatus (the pictures probably make this more clear). Finally, the pot has a permanently attached heat exchanger on the bottom to more efficiently transfer heat to the contents of the pot.
The Primus Eta Solo Burner
The Eta Solo included a users manual in a variety of languages which describes in detail the assembly and operation of the stove, as well as safety considerations. I have to admit that I didn't immediately read the instruction manual as the stove assembly and operation was pretty obvious. Instructions for routine maintenance and service are detailed in the instructions as well, and are pretty typical. For example, if the stove is not operating properly, ensure that there is sufficient fuel in the canister, verify that the jet nipple is cleaned, or clean it by disassembling - the required wrench not included but readily available. There is, as with most similar stoves, also an O-ring which must be periodically maintained or replaced to ensure a proper seal. Primus does offer spare parts through their website and some authorized dealers.
As promised above, below is a summary of the component weights as I measured them. My scale has about a ½ oz (14 g) accuracy, so everything is rounded accordingly.
Based on this, the minimum weight of the setup is 13 oz (369 g), which would include the burner and the pot. It is probably possible to save a small fraction by leaving the pot jacket and lid at home, but the amount is so small that it doesn't register on my scale, so it's probably only important to the extremely weight conscious. This 13 oz (369 g) is also very close to the manufacturer's stated 12.9 oz (365 g), so perhaps the Primus measurement omits the optional items.
For the sake of completeness with respect to weight, I feel it is necessary to also include the fact that the fuel canister I purchased and plan to use with this stove weighed 7 oz (198 g) when I measured it full. This is a standard-sized 100 g (3.5 oz) canister, meaning that it contains 100 g (3.5 oz) of fuel, and the remaining weight is that of the container. Primus recommends the use of their fuel canisters with the Eta Solo. My local outfitter does not carry the Primus brand fuel, as a result I will test this stove with locally available fuel which is a pretty popular and widely available Butane-Propane-Isobutane blend.
I was unable to locate any warranty information in the product packaging or on the Primus website.
Out of the box, this stove appears similar to others in its class, though Primus did a nice job of adding some additional, nice-to-have features while still keeping the overall weight down and delivering very fast boil times.
I like the option to hang the whole setup, even though I can't immediately think of when I might use it in this configuration on a typical trip. My first thoughts were on a boat where stability would be affected by the boat pitching and rolling, or suspended half-way up a rock face where it might hang from an anchor. Since I typically stick to terra firma for the purposes of testing for BackpackGearTest.org, I'm not sure that the option is absolutely required for me, but I'll still attempt to find an occasion to try it out.
Another thing I appreciate about the Eta Solo is the fact that the burner and fuel canister can be stowed inside of the pot, with the lid on, for transport. I can also fit the heat shield and pot supports in there if required, but I haven't figured out how to include the hanger or the gas canister legs as they are just too oddly shaped, even when broken down.
Although Primus targets the Eta Solo for one or two person use, the fact that it can be converted to a conventional stove and used with a different pot or pan means that it could serve a larger party in a pinch. Add the fact that the weight penalty for the conversion kit is relatively small and this becomes a really nice feature.
Once I had a chance to play around with the stove's various configurations, I filled the pot with water and took it outside for a test burn. The stove took my 16 oz (470 ml) of water from 67 F (19 C) to a rapid, rolling boil in just under two minutes on full gas. As a long time liquid fuel user who recently converted to alcohol burners, I was amazed at how fast this stove boiled water. The manufacturer claims a 2.1 minute boil time for 0.5 L (17 oz) of water, which is more or less consistent with my first experience.
The stove was very simple to light - a little gas and a few clicks of the piezoelectric igniter button and operation was just as simple. I just turned up the gas to full open, set the whole kit down on my deck, and watched the thermometer I had stuck through the hole in the lid. Turns out I didn't really need the thermometer, because once the water got hot enough to boil it was pretty obvious, as the stove and pot were gently agitated from within by the boiling water. At that point I noted the time and turned the fuel valve off. I was able to grab the pot without burning my hands thanks to the wrap-around cover, but it was definitely hot. Using the webbing handle seemed a little more reasonable. I peeled off the lid, almost scalded myself with steam, and dumped the burning hot water into my yard.
Within a few short minutes everything was cool enough to the touch that I was able to re-pack the burner, then the heat shield and pot supports, and finally the gas canister, back into the pot. The lid deforms just a bit with everything packed inside, but still stays on securely.
I'm looking forward to getting this stove out into the field for some additional testing, as well as to try it out in some of its other configurations.
12 October 2010
I've had a wonderful summer and fall with the Eta Solo. It has traveled with me on four different backpacking trips totalling 13 days of use. I've also taken it along on two car camping trips, where I used it to boil water for various purposes, including making coffee and dish washing. All of these trips were in my usual locations (so much for variety being the spice of life) - the Allegheny National Forest in Pennsylvania and the Zaleski State Forest in Ohio. The car camping trips were to a local state park (Findley State Park in Ohio).
The author can be a little grumpy
The weather was pretty decent on all of these trips - I did encounter a little rain on one of the Allegheny National Forest trips, but was able to take refuge under my tarp and cook and relax in relative dryness. As for temperatures, the weather has been mostly warm, though I did encounter some nighttime lows down to around 40 F (4 C) - not cold enough to noticeably impact the operation of the Eta Solo stove, however.
As far as cooking style is concerned, I'm a water boiler and prefer not to do dishes - especially when backpacking - so the majority of my uses of this stove have been to boil water for freezer bag-style cooking or making coffee. In total, I think I've boiled almost 5 gallons (19 L) of water with the Eta Solo, if I did the math correctly.
This stove is fast! So fast, in fact, that I've learned that I have to keep a close eye on it or risk having the water boil over. I have to admit that I'm more used to liquid fuel stoves and alcohol stoves than canister stoves like the Eta Solo, so I'm considering one such accident part of my learning curve (much like learning to properly prime a liquid fuel stove without sending massive flames skyward). The first time I took the Eta Solo out was on a car camping trip with my daughter, another friend of mine, and his daughter. I wanted to try out the "hanging" configuration and found a suitable tree limb with which to practice. After making sure that the tree wouldn't be harmed by the stove, I dropped in a tea bag o' coffee, snapped on the lid, and went about my camp chores. Not a few seconds after I turned my back until I hear the sound of a rocket preparing for takeoff. In reality the stove was viciously boiling over - sputtering my not-quite-ready-yet coffee all the outside of the stove and onto the ground. By the time I reached the stove it had put itself out and boiled the cup basically dry. I quickly turned off the gas and took the coffee-soaked stove off the hanger. I've never seen such a violent display from a backpacking stove. I'm not sure if it was accelerated by the coffee or what, but certainly a good lesson to learn. From there on out I now simply light the stove, and sit there and watch it so that I can turn it off as soon as it starts to boil.
Much better thanks to the
After my initial trials, I find the operation of the stove quite simple. Assembly is very fast, and lighting the stove is easy. I do wish that the button for the piezo igniter was a little larger, and that the fuel control valve was a little bigger, but in general it is very easy to operate.
The Eta Solo packs nicely into my backpack - I simply put the burner assembly inside of the cup, followed by my fuel canister, snap on the lid, and drop into my pack. I've found that I generally don't use the support legs for the fuel canister - I've been fortunate enough to have a flat enough spot in most instances. I also have only used the "foreign pot" configuration - comprising the pot stands and heat reflector - on a few occasions, and only to show a hiking partner how it works. I also don't really use the hanging configuration either, aside from my initial attempt and a few other times just to get it figured out. This would probably be ideal for someone on a big-wall rock climbing expedition or in a particularly sensitive environment where it's poor form to have anything hot near the ground.
I'm not sure if I've rattled something loose or if it's just a normal part of these types of igniters, but I do find that the piezo-electric igniter sometimes fails to spark due to the gap between the end of the igniter needle and the top of the burner being too large. I'm now in the habit of checking the spark before I even screw the gas canister on and adjusting (that's bending to us non-scientific types) the gap until it sparks consistently.
As far as I can tell, the Eta Solo sips fuel. I've been trying to weigh the fuel canister when I return from every trip so that I can estimate the amount of fuel used, but in reality I'm trying to measure something smaller than my scale's accuracy. I'll try to report on the total amount of fuel used over the entire testing timeframe during my long term report, where hopefully I will have emptied a canister and can estimate how much water I've boiled with that amount of gas.
Long Term Report
14 December 2010
Long-Term Use Summary
I took the Eta Solo along on one more weekend backpacking trip to the Allegheny National Forest, as well as on a car camping trip to Cook Forest - both in Pennsylvania. Those two trips bring my backpacking use to 15 days and total use to over 20 days. I made 2 full cups of coffee every morning on the Eta Solo, whether backpacking or car camping, which means that I've used the stove to make about 48 oz of coffee times 20 days, or the equivalent of around 10 pots of coffee, plus or minus some as I occasionally made a little less or make an extra cup full to share. I also tend to have a hot breakfast (oatmeal) when backpacking, so I've used the stove to make around 30 packets of instant oatmeal (at least 2 packets per breakfast for me). I only have a hot lunch in the coldest parts of winter and I don't believe I ever used the Eta Solo to make lunch. I have made a bunch of dinners on it, however. For dinner I just boil water a cup full of water and add as much as I need to my meal, and so I've made around 18 dinners with the stove. Add in the occasional cup of hot chocolate, coffee, or other instant drink in the evening for another roughly 10 uses. Adding all that up, I estimate that I've boiled somewhere around 13 gallons (49 L) of water with the Eta Solo.
All of that math, so that I can estimate how much fuel I'm using when I turn on the Eta Solo. My digital scale is accurate to about 0.5 oz (14 g), and the total weight of gas starting out in the canister I used was 3.5 oz (100 g). The canister is still going, but barely. I weighed the canister and measaured the remaining gas at 0.5 oz (14 g) - which also happens to be within the accuracy of my scale. So while the stove still lights and burns with this canister, I'll probably buy a new one before my next trip. Obviously, all of this depends on the starting temperature of the water, the ambient temperature, the length of time that the stove is running, the temperature of the gas canister, and a whole lot of additional variables that I can't control. Any way I think about it, though, it seems unrealistically high to think I've boiled that much water on so little fuel. Without repeating the test in a controlled environment (what fun is that?), I'm not sure I have confidence in those numbers.
Outside of testing though, I only really want to know how much fuel I burn on average so I can be sure that I won't run out halfway through a trip. Since most of my trips are weekend length, the risk is somewhat minimized. And since I do still use the stove when car camping, I can bring along what I think are the almost-empty canisters to use them up on those trips. For longer trips when I decide to take the Eta Solo in the future, I'm sure I'll build some model or something to predict how much fuel I'll use, factor in the weights of the various stoves I own, and make a determination of which set to use based on the total weight of the stove plus the fuel. With a few exceptions the Eta Solo will likely be at the top of that list.
Long Term Observations
Where the plastic insulation around the igniter is broken away
I'm not sure what caused the plastic to break, but I can only assume it was from getting banged around inside my pack. I don't recall dropping the stove or otherwise abusing it. In fact, I feel like I've been pretty kind and gentle to it. As soon as I figure out what I can wrap around the exposed pin to insulate it that also won't burn when the stove is running, I'll fix it at home. My initial inclinations were to try electrical tape or a piece of a straw, though I fear both might melt when the stove is on. Perhaps I can find some higher temperature shrink tubing or try a duct tape repair. In the meantime, however, I can always light it by hand or hold the stove in such a way as to get it to work.
The Primus Eta Solo Stove has been a fantastic piece of kit for me. It boils water really fast which is nice when I'm in need of my morning coffee, and means that I'm eating my noodles while my hiking pals are still trying to figure out where they packed their wind screens. Because I generally transfer the hot water into a freezer bag for my actual cooking, I don't really have anything to report in regards to clean-up. It's just water, or sometimes coffee-flavored water in there, so I wipe it out, drop in the burner and fuel canister, snap on the lid, and go. I now normally leave the cables for hanging the pot at home, as well as the fuel canister support legs. I don't really ever use the pot stands and heat shield, so those have been relegated to the spare parts bin as well, except for future trips with large groups where it would make sense to boil large pots of soup or something.
I would like to thank Primus and BackpackGearTest.org for the opportunity to test the Eta Solo stove.
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