Anonymous wrote:We live in a (to put it mildly) risk-averse society!

Insurance and lawyer run society... Insurance wants only to insure companies that can't be sued... lawyers are looking for new things to sue for. Or something like that.

Note: not all insurance companies and not all lawyers

I have noticed that too, Annie, when there is less than a quarter left in the canister. However, I have not connected it with the idea that the fuel has become weaker. The glass matting-like stuff in the alcohol canister appears to have a strong wick-effect and thus spreads the fuel around in this material. As the canisters is nearing empty, the wick material will naturally turn drier and the stove will burn with less intensity.
I might be wrong, but this is my conclusion about it.

It takes a real fool to produce a run-away alcohol fire in that stove. Still, I have a fire blanket at hand, in addition to my 5-litre cans of water.

Arne

PS: In the specs for the Origo, it says that a canister takes 1.2l alcohol. With my 1l-bottles, it is natural to only fill with one litre. This lets me sail Ingeborg on her ear without fearing fuel spill, even if my stove is not gimballed.

This is a logical explanation, Arne. Using David's method of measuring the alcohol content, it would be interesting to try testing the fuel now and then for it's alcohol content.I have a feeling the alcohol will evapourate faster than the water, but it would be fun to test that. Certainly a wee dram (or fine Norwegian akvavit!) is best sampled shortly after pouring, whether diluted or not...

Oh the fun I'm going to have with my new stove :)  

Frankly, I don’t buy that explanation. ‘Cleaning alcohol’ is probably just some alcohol-water mix. Alcohol and water will not split in a tank (unlike milk and cream in un-treaded milk).
I can only think of two ways that the alcohol in the canister gets weaker over time.

• 1.      The (unpadded) canister of alcohol attracts moist from the air, which dilutes it.
• 2.      The (unpadded) canister lets alcohol evaporate. If the alcohol is more volatile than the water, the water may not evaporate as fast, and then the alcohol contents will drop.

In any case, I think this is most likely to happen if the stove is sitting idle for some time between use.
My armchair, amateur guess is that this (diluting) process, suggested in case #1 or #2, will happen just as well with the pure 96% alcohol.

Still, I will keep this note in mind. Next time one of my burners run empty, I will dry the canister over low heat before filling it. I will also weigh the canister on my digital scales before and after the drying process.
Too bad I have no ways of actually measuring the strength of the alcohol.

Btw...
The reason why I think that the 80% alcohol is better on the Origo, is that this burner has limitations on the air-fuel mix. At full power there is simply not enough oxygen around to keep the flame blue (=full combustion). This means that some of the alcohol is only half-burnt, and the un-burnt part is soot. By reducing the strength of spirit to 80%, there will be fewer alcohol molecules searching for oxygen to react with, so this is like reducing the power setting. Maybe that would be just as good  -  reduce the power setting a little. This automatically leads to a leaner, and thus cleaner burn of the Origo, just because of the way that burner has been built.

Arne

PS: I can imagine that Annie Hill does not have problems with the burners getting weaker, since she uses her stove all the time

Compass24 never responded to our emails about the fire onboard from their shoddy Origo3000 copy last year, but they obviously took on our feedback and the product description (this is not small-print, it's the main info!) now makes it quite clear that it is unsuitable inside or on a boat, and a fire is your fault for not following the instructions to the letter:

Please observe the following instructions when operating the spirit cooker: -Don't operate the alcohol cooker unattended and never in closed rooms. -Make sure that the cooker cannot tip over and is placed on a fireproof base. -Make sure that the cooker has enough space on all sides, as the cooking pot deflects the flame and heat to the side. -Make sure that the stainless steel springs under the burner pots are high enough so that the burner pot is flush with the lid. -Check your camping cooker before each use for visible damage or other defects that could lead to malfunction. -Children should only stay near the cooker during operation under supervision. -Have fire extinguishing materials ready. A fire blanket or small fire extinguisher is best suited for this purpose. -Read the operating instructions and make sure that you operate your cooker in accordance with the manufacturer's instructions.