Quoted from vid1900:I leave them sealed in glass jars.
At some point in the future, someone may figure out how to filter the liquid, and nothing flows better than those old toxic lamps.
Mechanical filtration alone will not fix the cloudy liquid (because the cloudiness is due to emulsification of the “lava” in the solution, rather than suspended solid particulates), so de-emulsification is required, which is a complex process that requires specialized (expensive) thin-film polymer-based micro-membranes and is probably out of the scope of the majority of hobbyists.
Original 1960’s lava formulation consisted of paraffin wax+mineral oil+carbon tetrachloride; the CCl4 is the key ingredient that modifies the wax’s buoyancy in water to just the right degree to endow it with its unique floating characteristics. Problem is, CCl4 is carcinogenic, mutagenic (causes birth-defects), and significantly toxic to liver, nervous system, and bone marrow, and was therefore highly regulated starting in the early 70’s.
The replacement formula is a “trade secret”, but it simply doesn’t seem to work as well; the lava flow is good, but it tends to emulsify a lot more readily and is much slower to clear (if it does so at all). I recall a case study in the 90s where someone ingested the contents of a late-80s lamp (alcoholic looking for a substitute for booze) and suffered acute kidney failure; I don’t remember all the specifics, but they determined that the contents included chlorinated paraffin, mineral oil, kerosene, and low molecular weight polyethylene glycol, and concluded that the PEG was likely responsible for the toxic effects (he needed dialysis for a time but recovered).
The black ferrofluid-based lamps shouldn’t be too toxic. Typical ferrofluid consists of magnetite nanoparticles coated in surfactant (often oleic acid, soy lecithin, or citric acid) and suspended in water or kerosene and isn’t terribly toxic if ingested, however it will irritate skin and eyes and permanently stain most surfaces.