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You should not do anything to annoy your neighbors or cause a fire hazard. The timeyou need to reduce the kerosene depends on how hot you make it. I have only done it quite slowly at lowish temperatures (150C or so) for several hours. You do not want it to boil. It will smell less at lower temperatures, but will still be noticable.
If your ferrofluid floats, that indicates it has too much hydrocarbon (kerosene) vehicle relative to the iron oxide. You must reduce it. You will have to find a well ventilated place to do this; do you have a balcony? The kerosene fraction that volatilizes is not all thattoxic, but nothing you want in indoor air space where people can breathe it. Some third party suppliers of EFH1 cut it with additional kerosene, which is sleazy, and may be the source of your problem.
How have you cleaned the 'new glass'? I recommend cleaning with a harsh alkaline cleanser, heating in an oven, and soaking in vinegar. Just because glass is new does not mean it is well prepared..
The vinegar bottle is just soft soda lime glass, but the display at the museum was boro-silicate. Both types haveworked well for years.
The EFH1 from Ferrotec is the gold standard; the stuff from other sources is sometimes diluted with excess kerosene. Cooking the ferrofluid reduces the amount of light molecular weight components of the kerosene, which I think contribute to staining. I recommend cooking down to get a fairly viscous ferrorluid; you will probably lose 20% of the original ferrofluid. I don't have quanititative data, partly because what I did worked so well. Let me know your results.
Really Beautiful Swimming FerrofluidsView Instructable »