firing a new mold

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Paul Schulz
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firing a new mold

Post by Paul Schulz »

hi guys i have some new ceramics mold up to 340 mm wide that i need to pre fire, but not sure about the firing rate and time . one program says a rate of 50c per hour to 800c ,,that's 16 hours ,,is this right ?? many thanks paul
rosanna gusler
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Re: firing a new mold

Post by rosanna gusler »

need more info. are you firing green ceramics? if not i see no need to prefire. just kilnwash and use. r.
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lorimendenhall
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Re: firing a new mold

Post by lorimendenhall »

I've never pre-fired a mold BUT I just got a new one and the instructions say:

"pre-firing is recommended for molds larger than 30cm. this process strengthens the inner structures and makes the mold less susceptible to thermal shock." the directions are to go like you say below, 50 degrees C (122F) to 800 degrees C (1472F). no hold. let cool down at room temp. yes, that sounds like it would 16 hours to get to the temp but then it would take quite a few hours to cool back down to room temp.
rosanna gusler
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Re: firing a new mold

Post by rosanna gusler »

What manufacturer recommends That? It makes no sense to me. R.
artist, owner of wanchese art studio, marine finisher
lorimendenhall
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Re: firing a new mold

Post by lorimendenhall »

this mold is manufactured by Creative Ceramics and I think it was a Bullseye branded item.
rosanna gusler
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Re: firing a new mold

Post by rosanna gusler »

huh. if the mold has been bisque fired. (those have) then it has been fired to above 1472. i can see no reason why doing like they said would do anything to the ceramic 'interior structures' or whatever. i just see no science behind that statement. cynthia m, you got a clue i am missing? r.
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Glass Fever
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Re: firing a new mold

Post by Glass Fever »

rosanna gusler wrote:huh. if the mold has been bisque fired. (those have) then it has been fired to above 1472. i can see no reason why doing like they said would do anything to the ceramic 'interior structures' or whatever. i just see no science behind that statement. cynthia m, you got a clue i am missing? r.
As a sometimes potter I agree with Rosanna. Firing an already bisqued mold to basically bisque temperature will do nothing to the internal structure. I have never prefired any of my Bullseye or other purchased molds.
Paul Schulz
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Re: firing a new mold

Post by Paul Schulz »

mmmm seems i have opened Pandora's box ,,the moulds are from creative ceramics and 15 " round or across. the instructions say to pre fire at a rate of 50c per hour to 800c ,time 960 minutes ,,the trouble with this program is that my kiln controller will not handle that as it is just too slow,,,,,,so to pre fire or not to pre fire
Brock
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Re: firing a new mold

Post by Brock »

Not. I never have and had a lot of those molds.
Laurie Spray
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Re: firing a new mold

Post by Laurie Spray »

Makes you wonder what they are firing these slip cast molds to on their firing. There should be no need to fire it again. We bisque our thrown molds to 1900 and they last forever but they are a different clay body.
I would not prefire.
Laurie Spray

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