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Drying a Mold Quickly: Home dehumidifier vs drying cabinet?


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#1 lemonade

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Posted 23 March 2013 - 03:20 PM

I'm making some plaster molds for slip casting and hoping to get them dry as soon as possible.

My school has a drying cabinet which consists of a space heater and one of those big square electric fans blowing into basically a steel filing cabinet. It's very homemade but seems to work well enough for everyone's molds.

At home I have a normal dehumidifier which can get the air down to below 30% humidity and outputs a bit of heat. I've had success drying paint overnight if I put the dehumidifier in a closet. Can I use the dehumidifier in combination with short spells in the oven at low temperature?

Which one of these is a better option for drying my molds? Are they even remotely comparable?

Thanks

#2 justanassembler

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Posted 23 March 2013 - 06:21 PM

I'm making some plaster molds for slip casting and hoping to get them dry as soon as possible.

My school has a drying cabinet which consists of a space heater and one of those big square electric fans blowing into basically a steel filing cabinet. It's very homemade but seems to work well enough for everyone's molds.

At home I have a normal dehumidifier which can get the air down to below 30% humidity and outputs a bit of heat. I've had success drying paint overnight if I put the dehumidifier in a closet. Can I use the dehumidifier in combination with short spells in the oven at low temperature?

Which one of these is a better option for drying my molds? Are they even remotely comparable?

Thanks

avoid your oven, its too easy to overheat and ruin your plaster.

#3 Denice

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Posted 23 March 2013 - 06:51 PM

I have used a oven when the humidity is so high I can't get a mold to dry, I had read an article that you can dry plaster in a oven at 180 degree oven. I usually leave the mold in the oven untill it's warm and then I take it out and let it cool and then put it back. How long you leave it depends in the size of it and the thickness of the plaster. You do need to careful and check on it often or you will ruin the plasters life expectancy. Denice

#4 Mark C.

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Posted 24 March 2013 - 06:40 PM

Back when I ran a slip casting business on the side of my regular pottery business we would never heat the new molds but would blow air over them while straped together tight. I favor the dehumidifier over heat.
You do not want them to dry them to fast or cook them with to much heat.
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#5 perkolator

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Posted 25 March 2013 - 12:36 PM

transpiration by use of warm air flow will be your quickest solution to getting them dried out. the dehumidifier might work if it blows a decent amount of air - i'm unfamiliar with them being from CA. usually, when our large classes make lots of molds, I usually set up an area with 1-2 space heaters and 1-2 box fans to warm up the air and get some circulation. molds get good airflow by propping them up on sticks or bricks. for smaller batches of molds, they go into an open-lid electric kiln set around 120* with the vent turned on. the fan method dries them out at least a 1-2 days faster from observation.

no matter what - if you use heat to dry the mold you don't want to go with too much or you can compromise the plaster's strength.

#6 MadMudder

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Posted 26 March 2013 - 10:43 PM

Put them in a 200 degree oven for a few hours and let them dry out.
200 degrees is not that hot.
They also dry really well on a dry sidewalk in the sunshine.
I make many molds and never have problems with the side walk or the oven. I try not to have the smooth molding side directly on any cement. Brace it up with 2x2s or something a piece of foam.
Slump and Hump molds are my favorite! They are kind of hard to find and The Big Ceramic Store has a bunch of them.

http://www.bigcerami...s/SlumpHump.htm

Sadly I found a couple more I may need....

MM
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#7 Diana Ferreira

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Posted 27 March 2013 - 12:15 PM

I have a little box (with air vents) and a fan heater that moves and blows warm air. It's got a thermostat, and will shut down if it gets too hot inside the box. Most molds (small and medium) dries overnight.

Plaster molds that fits into a microwave could be dried out in that. Defrost or low setting, about 10 minutes at a go. (My ex, a professional modeller and moldmaker) taught me that trick.
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#8 Essaily

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Posted 27 March 2013 - 09:36 PM

REcently I made a slab plaster for drying my scraps and discovered a Spanish sulptor who discovered a method of setting plaster in 5 minutes rather than 30 minutes. This was quite exciting idea and tried it and it worked just as he suggested.
Simply add 1% finely ground already set plaster into your mixture and it will quickly set. Adding more finely set plaster speeds up the setting time, though I'm not sure how it affects the drying off time. All the best with that!

#9 Diana Ferreira

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Posted 28 March 2013 - 03:31 PM

I am aware that particles of already set plaster will increase the setting time of plaster. For that reason it is important to clean your mixing bucket very well. I use a sieve when I cast to make a master. Lumps in the plaster will cause an uneven hardness in the setting plaster, and make it difficult to cut evenly. When making a mold (for casting clay) you also have to make sure that the plaster is evenly mixed, as lumpy areas might affect the absorption rate of the water from the clay. It can give uneven casting jobs. But I am sure that mixing in preset plaster can have applications in other things. I prefer to add luke warm water to my plaster.
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#10 perkolator

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Posted 01 April 2013 - 01:48 PM

Put them in a 200 degree oven for a few hours and let them dry out.
200 degrees is not that hot.
They also dry really well on a dry sidewalk in the sunshine.
I make many molds and never have problems with the side walk or the oven. I try not to have the smooth molding side directly on any cement. Brace it up with 2x2s or something a piece of foam.
Slump and Hump molds are my favorite! They are kind of hard to find and The Big Ceramic Store has a bunch of them.

http://www.bigcerami...s/SlumpHump.htm

Sadly I found a couple more I may need....

MM


200* is too high in a regular oven. it's too close to the boiling point of water (212*) especially since ovens don't have enough dexterity to hold specific (or low) temps. very good chance of blowing up your wet plaster mold in this type of situation.

as for setting up plaster faster, there are 3 ways -- already cured plaster added, warm/hot water, and lots of agitation.




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