Safe postcure oven

Given the cold conditions we’ve had lately I very much would like a (post)cure oven (Still need to insulate my workspace to be able to get the temperature up to epoxy working temp, but that’s a different story). The thing that worries me (not to mention my wife) is that I will have to leave it on through the night or when at work. A few different ovens have been posted here, but none of them strike me as safe. Given that I’ve had to change the plug on a couple of electric room heaters because the cable started to melt, I worry. Does anyone have any suggestions for a way to build a relatively safe oven at relatively low cost with regards to materials, insulation and heatsource?

Well I've used underfloor insulaton eps sheets and two 250 watt heat lamps. Foam has not melted at all and seems to be safe. Easily gets to 40*C. But I don't leave home for long with it going.

Greenlight (Brian) did a thread almost a year ago…

El Cheapo Epoxy Postcure Box

Good for the backyarder.

If you are committed to not running a heat source (ie gas/wood burning or electric heaters) for several hours when you are out,  the only thing that can be done is to pre-heat it, then turn off your heat source before you leave the house.

Then there are two methods of maintaining the temp. for a long period without a heat source:

1)The coffin should be super insulated

2)Inside the insulated coffin you should have a lot of mass.  Heat transfer is a function of mass.  When a refrigerator is unplugged, it will loose its coolness quickly if it is empty, but when it is full it can maintain the temp for a long time.  At the bottom of a highly insulated coffin, I would throw in a bunch of scrap metal (iron based metal, like steel rebar).  100lbs of scrap steel(or bricks, but bricks will take up twice as much space as steel) heated to 60Celsius will probably maintain a good temp for a long time…if it is well insulated.  100lbs of scrap steel is 20% the size of a performance board.  You could probably put 500lbs of scrap steel (the same size as a performance board) and that would keep it warm 24hrs, easily.  Scrap steel is free at a lot steel yards or  $30/100lbs at Target:

http://www.target.com/gp/detail.html/191-7379764-3739619?asin=B000BB8Y92&AFID=Froogle_df&LNM=|B000BB8Y92&CPNG=sports&ref=tgt_adv_XSG10001

Heating up the steel and using heat diffusion to keep the box warm is roughly the same total amount of energy consumption as using a steady energy consumptive heat source.

I’m making one in my workshop at the moment and plan on using vivarium heat mats in the bottom and run them through a thermostat. Cheap to run and if they are safe enough to put in with your pets then thats good enough for me.

Hi,

interesting idea, like old-fashioned cooking with a cooking stone. However I have not ruled out electric heating, but I’d prefer a heat source with low effect (to prevent the cable from overheating) and low surface temperature. This pretty much rules out fan room heaters, hair dryers and heat bulbs. Since I want to use a heater with low effect, the insulation needs to be good, but ideally it should also be hard to ignite. That goes for the box itself too.

Been thinking about using a boot dryer rack like this as it has low surface temperature and can supposedly be covered completely without catching on fire, on the other hand it’s a bit pricey for something that gives off about as much heat as an oldfashioned lightbulb or two. Another alternative is wood floor heating system with thermostat which is pretty much ideal, but get’s real expensive real fast. As for the insulation, I’m thinking of using glass or rock wool rather than polystyrene based foam. As for the outer box, I don’t know but cardboard isn’t exactly fireproof?