John Rodgers on thu 30 dec 04
Pam,
Back when I was making all the molds for my shop in Alaska, new molds
were put on racks that allowed the air to circulate completely around
them. We would set the thermostat in the room at 80 degrees, and then
turn on several oscillating fans to circulate the air. We never put the
fans to blow directly on the molds. That warm circulating air would dry
small molds in a week, and larger molds in 10 days to two weeks. It
would take longer at cooler temperatures.
Molds should be completely dry before use. Complete dryness may be
determined fairly closely by touch. Any coolness indicates the mold is
not completely dry. Often times I would wait a few more days just to be
sure.
First time use of a mold sometimes results in stuck greenware. Seems the
mold needs to absorb some chemicals from the clay to cure the mold
surface for best performance. So be prepared to make a piece or to
before the mold performs well.
Regards,
John Rodgers
Chelsea, AL
pam wrote:
>I made some plaster molds a couple of days ago, and I am wondering how long
>they should age/cure before I attempt to use them for their maiden voyage?
>
>I made plaster bats last summer, when it was very humid, and they took 2
>weeks before they worked well. (I at first thought I had made them wrong,
>wet clay just
>
>would not stick like it should). So, would a dry winter make these molds
>ready faster?
>
>Pam, enjoying a rare few warm days in December, which is why I went outside
>and made plaster molds the other day :-)
>
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>
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>
>
>
>
pam on thu 30 dec 04
I made some plaster molds a couple of days ago, and I am wondering how long
they should age/cure before I attempt to use them for their maiden voyage?
I made plaster bats last summer, when it was very humid, and they took 2
weeks before they worked well. (I at first thought I had made them wrong,
wet clay just
would not stick like it should). So, would a dry winter make these molds
ready faster?
Pam, enjoying a rare few warm days in December, which is why I went outside
and made plaster molds the other day :-)
Warren Heintz on thu 30 dec 04
As long as they are cool to the touch they have moisture in them,sometimes difficult to tell during the winter. I have put them in my kitchen oven,after having sat out a day or two, to dry them out,much to the aggravation of my better half,but it does make short order of the drying.
pam wrote:I made some plaster molds a couple of days ago, and I am wondering how long
they should age/cure before I attempt to use them for their maiden voyage?
I made plaster bats last summer, when it was very humid, and they took 2
weeks before they worked well. (I at first thought I had made them wrong,
wet clay just
would not stick like it should). So, would a dry winter make these molds
ready faster?
Pam, enjoying a rare few warm days in December, which is why I went outside
and made plaster molds the other day :-)
______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
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pam on fri 31 dec 04
Well drat, after 4 days, they are still colder than my cat's heart, so I
guess they are not ready yet. Thanks for the pointers, I will just have to
be patient!
Pam, were we had another wonderful warm day here in KC, but the weatherman
warns that trouble is a commin'
Eleanora Eden on fri 31 dec 04
Hi Pam and all,
I use the put-it-to-my-cheek test. If it feels cold at all it is not
ready yet.
I like to make molds when the wood stove is being used. I put the
molds near enough to warm them but not near enough to warp them.
Otherwise I put them in a sunny window.
To dry between uses all my molds are on a wall rack made of 1" used
drainpipe, same as the big ware rack. Air on all sides they are
ready to re-use in afew days.
Without a heat source mine take about 2 weeks to be ready to go also.
Eleanora
>I made some plaster molds a couple of days ago, and I am wondering how long
>they should age/cure before I attempt to use them for their maiden voyage?
>
>I made plaster bats last summer, when it was very humid, and they took 2
>weeks before they worked well. (I at first thought I had made them wrong,
>wet clay just
>
>would not stick like it should). So, would a dry winter make these molds
>ready faster?
>
>Pam, enjoying a rare few warm days in December, which is why I went outside
>and made plaster molds the other day :-)
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
Ama Menec on wed 5 jan 05
Hi Pam,
I'm able to use my moulds next day after casting them, but this may be
because I use Herculite Plaster and not Potters Plaster. I use this because
I press mould, not slip cast. Occasionally I have used them within a few
hours but mostly I leave them overnight and they're ready to clean up and
then use later that day...and I'm in damp Devon! Good luck with your
project.
Ama, Totnes, Devon, UK.
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John Jensen on wed 5 jan 05
My experience, and the books I've read suggest a week of slow drying.
Fairly massive molds might benefit from two weeks drying time.
John Jensen, Mudbug Pottery
John Jensen@mudbugpottery.com
http://www.toadhouse.com www://www.mudbugpottery.com
Subject: Re: Speaking of plaster, how long should new molds cure?
Hi Pam,
I'm able to use my moulds next day after casting them, but this may be
because I use Herculite Plaster and not Potters Plaster. I use this because
I press mould, not slip cast. Occasionally I have used them within a few
hours but mostly I leave them overnight and they're ready to clean up and
then use later that day...and I'm in damp Devon! Good luck with your
project.
Ama, Totnes, Devon, UK.
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