I know nothing about oil expellers, but my first thought was a heat gun. Mine has two settings and different size nozzles for the end do you can concentrate the heat.

I was about to say heat gun, and now I see Justin's already suggested it. The one I worked with in college had a flat plate on top so I could put it down while it was still on. This was handy because I was melting crayons on to a sculpture and then smoothing them out, which really took to hands. ~Molly

A mantle of hot water should do the trick. It doesn't smell, conducts heat well and has a built-in temperature limit as long as you don't pressurize it. Take e.g. a used tin can, make two holes in the sides so you can stick the expeller through it. Seal the holes with silicone. Pour in boiling water and start expelling. Replace the hot water when it cools down too much.

Alternatively, try a small propane, butane or natural gas burner. Those burn without smoke or smell but quite hot. Don't put any flames too close to the paint, though. Unless it's an enamel (glass), the paint (using an organic binder) will burn at some point. But if the expeller gets that hot, the oil will also get too hot and pyrolyse.

Good ideas, everybody! That should give us a lot of ideas to work with. I'm actually most intrigued by Roland's boiling water suggestion, although it does sound the hardest to implement the first time.

Can you put the expeller on top of the stove? Metal-to-metal contact and airflow would then heat it up. It might get too hot, though.

Pre-heating the oilseeds in e.g. a frying pan on top of the stove might make expelling easier. The vicosity of the oil will decrease markedly as the temperature increases.

Mark's been researching, and someone extracts coconut oil by heating up the coconut lightly, then passing it through a juicer. I like that idea the best so far!

(Actually, maybe with preheating, you could send it through the expeller with no heat added? That's probably what you were saying....)

Heating the seeds is probably not nearly sufficient. to heat up the expeller. The specific heat of organics is higher than that of iron, but there is a lot more iron in the expeller than oilseeds!

But pre-heating the seeds would reduce the amount of heat that you need to add to the expeller. But on second thought, it is probably more effort than it is worth.

Clamping the metal base of the expeller to the hot stove might do the trick, though. Iron conducts heat very well. Much better than air or water.

Amazon has a 200 Watt magnetic heater which may be a bit too much: http://www.amazon.com/Kats-1153-Handi-Heat-Magnetic-Heater/dp/B000BOABS6

This link shows the Piteba with an oil pan heater: http://advancedsurvivalguide.com/2011/11/04/piteba-oil-press-pumpkin-seed-trial/

Electrical heaters: http://www.honeywon.com

Engine pad heaters: http://www.engineheaters.co.uk/

Selfadhesive heatermat,50W 100x150mm: http://uk.rs-online.com/web/p/products/0245613/

Touch-Safe Heater 50 to 150 W: http://www.omega.co.uk/ppt/pptsc.asp?ref=CS060_Series&Nav=

Good luck!

Cheers, John

Roland and John --- Good ideas! I suspect you'll hear more about Mark's next round of trials next week.

@John's comments are dead on. In industry, we typically use a steam jacket or other large-scale heat source for this, but using an engine pad heater attached to a lamp dimmer will give you an adjustable electric heat source. If you have a hot water or steam source (ie set up a kettle and hot plate/oil burner as a thermosiphon heater) you can wind copper tubing around the housing. Remember that the oil is carrying away heat as it leaves the expeller, so you'll need more heat than intuition would suggest - it's likely that a pipe heater won't do the trick.

If you felt adventurous, you could delve into winding the housing itself for induction heating, but that's not for the faint of heart.

If the only problem was the soldering iron's plastic melting, why not try a similar setup with a clothes iron?

I was thinking that if the original heat source was that small oil lamp, then you might want to consider steam or double boiler type heat.

Could you combine the boiling water idea with a rocket stove somehow? I suppose flames near oil is maybe something you would want to avoid. It would turn it into an outdoor activity, but heating it with small sticks as fuel seems like a good idea in any situation.

You could wind a nichrome wire around it. Tack it on with some silicone sealant/adhesive and perhaps insulate it for added efficiency. Should be run on a 12V DC source (depending on the length and heat needed).