solvent 50 works in zippos so i guess that would work but i guess you would also need to work in a chem lab too :-D
I bought my wife one of these a while back, and she loves it.
The thing that causes the combustion is a catalyst, and just like the ones in car exhausts nowadays a catalyst can be 'poisoned'.
Normally a catalyst takes part only temporarily in a chemical reaction, and so it isn't consumed. However some things can react permanently with a catalyst and then its performance may be very much impaired, or it may cease to perform altogether. Impurities in the fuel may poison the catalyst. That's one reason we have unleaded fuel now, the lead would destroy the catalytic converters in cars. Lead is quite commonly found as an impurity in petrochemicals. Zippo are quite clear that using any fuel other than their own will void their warranty, I imagine that their source for the fuel has guaranteed a low lead content, amongst other things, in the fuel.
I wouldn't worry much about using other lighter fuels, but I don't know what their manufacturers specify about their products and I think it's still a risk; but using things like industrial solvents and panel wipes is probably asking for trouble. Using such things in a stove, out in the open air, is one thing, but in these hand warmers it's something entirely different. Not only are you risking the catalyst but your body is likely to be in close contact with the combustion products and you've no idea what they might contain. Yes, lighter fuel is expensive, but I reckon at UK prices it's about 20 pence for a 12 hour fill and I'm prepared to pay that so I don't get it in the neck from her indoors if she's outdoors and her hand warmer packs up.
