Drying Plaster Molds
Posted 22 November 2011 - 08:25 AM
Posted 22 November 2011 - 09:23 AM
Posted 22 November 2011 - 11:41 PM
Posted 26 November 2011 - 12:07 PM
I will try my best to remember to take some pics. I know I have promised this previously too :-(
Posted 17 March 2014 - 11:03 PM
I've been working with molds non-stop for about two months now at UF. The first mold I made (about 26 lb of plaster) took about two weeks to dry and be usable. Then was taught three methods of speeding up the process.
One is sun-drying. Obviously it's not great on a humid day, but if it's a hot, sunny day it can definitely make some progress. I recommend putting them in front of a brick wall (or some other dark surface) facing the sun because it makes for a toasty atmosphere.
The second is kiln-drying. Set the kiln to hold at around 115*F and keep the lid propped. You don't want the mold to go over 120*F or it will recalcine.
The thirds, which I have found most helpful is using a dry/hot box. The one we have is pretty shoddy at the moment because it doesn't get too warm, but the ventilation is good. That's the key to drying these things. Heat it good, but you need ventilation to carry the moister away from the plaster.
I imagine rigging some sort of fan-and-heat combo would do the trick alright as well.
**REMEMBER when fast-drying plaster molds be sure to stand them upright, so that it is standing on the smallest surface area. This allows air to get all around the mold and prevents warping.
Posted 17 March 2014 - 11:40 PM
When we had a slip business on the side and poured 50-80 molds a day we just put a box fan (2feet x2feet) and let it push air over them at room temp. on the draing tables.
I live is high humid place in winter and it worked fine. The average temps are in the 50-60s
No heat just air movement and lots of it. We poured a new batch of them every other day so every day we had dry ones
Posted 18 March 2014 - 12:19 PM
I cast a large piece of plaster that was later cut up and carved as an accessory to a costume. point is after 2 days sitting out, it seemed no dryer than 8 hrs after i poured it. (it was cool wet rainy fall days)
We have a good size dehydrator that we can set the temp on. I put it in the dehydrator, set at like 100 deg. 10 hrs later it was perfectly dry.
Posted 18 March 2014 - 02:25 PM
A good drying box is a simple cardboard box with a 100 watt light bulb hanging in it to create a little warmth, with a fan blowing air through it.
Kiln Repair Tech
L&L Kilns Distributor
Owner, Neil Estrick Gallery, LLC
Posted 18 March 2014 - 04:21 PM
Newbie, I made some molds and I got the same problem.
Mine are small : 20 cm x 8 cm x 5 cm.
To dry them, I put them under my radiators and it work.
Problem with owen is that you speed the process to evaporate the water, but at the same time, you're damaging the molecular structure of the plaster.
So I'll suggest, if it's very humid, to dry them in a closed room, with temperature 20°C + air dryier.
Posted 28 March 2014 - 07:42 AM
The literature I've read suggests that drying plaster over 150 degrees causes the plaster to decalcify. As such I dry plaster in the 120-130 degree range. (Most forced air heaters come in at this range.) Air movment is also important. Like air movement causes our skin to dry out it also causes a plaster mold to dry out, as well.
When I'm casting lots of molds, and need them dry sooner than later, I create a box form, with metal shelves or sheets of plexi, and put a little room heater at one end. (Creating a heated tunnel, as it were.) This gives me heat and it gives me air movment. I can have molds dry, in just a day to two, this way.
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