[Vodkaman]

Everyone agrees that using the household oven is not a good idea. Commercial plaster operators use drying ovens. There is no reason why the small production/hobbyist cannot do the same. So I have introduced this thread so that we can brainstorm the problem and arrive at a workable solution.

I see the solution as a box, deep enough to mount a household bulb with sufficient air space around it. At the bulb end, a 2 inch dia hole. This is the air inlet. At the other end, a small 12v cooling fan (battery operated), as used for cooling computers. These fans move about 4 – 5 cubic feet per minute.

The plaster moulds would be mounted on wire racks, probably two deep, to occupy the space, thus increasing the airflow around them.

The box would be made of thin ply or chip board. It should be sealed because of the moisture and lined with aluminum foil, especially around the bulb. Long enough for your production needs. The required air gap around each cast is ½ inch. This figure will ensure a reasonable velocity of airflow. If the gap increases, the airflow slows. Redundant space could be packed out with wood or dummy boxes or even old castings. A removable lid for access.

The required temperature is 120°F, this should be easily achievable. I would suggest testing with a 40 watt bulb and measure the temperature. Adjust the wattage until a suitable temperature is obtained. The air inlet is positioned close to the bulb, this will help to prevent it from overheating in a confined space.

You could really get carried away with this design, with humidity sensors and temperature control, but that would be unnecessary complication. The best way to assess if the plaster is done is by weight. Weigh a new cast and weigh when dry. The percentage loss in weight will act a rough guide for future casts.

This box is not going to dry your casts in 30 minutes, but it will be faster than air drying. I would guess over night. The materials are cheap, everyone has an old computer lying around with a cooling fan inside. For someone who regularly produces plaster moulds, this box could be worth building, I hope someone tries it out.

[KcDano]

Good idea! Should be easy to build and produce good results.

[mjmmusser]

I throw my PoP molds in a 12 in. square cardboard box then set the top of my food dehydrator on it. Run in for 8 hours then pour.

[5BASSLIMIT]

Guys, How bout using a thermostat controlled heater that you would use in a incubator. I remember as a kid we had a box that we would put duck eggs in to keep them warm untill they hatched.

[Vodkaman]

It would work, but would take a lot longer without the airflow. The required temperature for ideal drying is 120°F . This temperature is little more than a hot room. The introduction of moving air keep the humidity at the PoP surface low and promote evaporation. All comercial ovens are based around an airflow.

[ensenada don]

An unused smoker might work.

[pirkfan]

This sounds a whole lot like the food dryer I built using plans from our local county extension agent. It used aluminum screens built by a local screen repair shop. They kept sets on hand just to fit the dryer.

[rossrods]

Hey Vodka, out in the field on construction sites when we couldnt get a microwave on the job we constructed a hot box, which was a wooded box made of plywood with a hinged lid on top, and took some 1" insultion foam board and glued it to the inside and on the outside of the foam applied aluminum foil so that the box would be lined to refelect heat, and installed a 100watt light bulb into a screw shell lamp holder, just the cheap plastic style thats in your attic, and plugged it into the nearest socket. We would put our food to be warmed up in around 9.00am and by 11.30am its ready to eat,

[Vodkaman]

Ross, good one. I've used a similar design when I used to do wine making. Heated by a 15w bulb and a thermostat to control the required tempreature.

I did not mention insulation, as the air will be in and out. But I think a lining of ALUMINIUM foil would not hurt any.

[mark poulson]

Couldn't you retrofit a large ice chest? It's already insulated, and the plastic ones are cheap.