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Topic: Quick answer on how long to bake please  (Read 1244 times)
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pookieb
« on: September 29, 2007 09:11:14 AM »

I am making horns that are about 1 1/2" tall and 1 1/4" wide.  That figures out to like an hour and a half for the thickest part, right?  Should I bake that long?  They're about to go in the oven and I have to leave at 2pm so please answer quick!  Thanks!!

Oh and it's black sculpeyIII, if that helps.
« Last Edit: September 29, 2007 09:11:50 AM by pookieb - Reason: added info » THIS ROCKS   Logged

Diane B.
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GlassAttic --polymer clay "encyclopedia"


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« Reply #1 on: September 29, 2007 10:10:04 AM »

First, if the horns are solid clay, that's a little bit of a problem... the thickest solid clay that's recommended for polymer clay items is 1 1/4".  The main problem is that items thicker than that can crack when baking (and of course, they'll take a lot longer to cure). 
Generally, for polymer things that will end up thick, an "armature" of some kind is used inside or underneath the clay to avoid having solid clay that thick (armatures and cores like tightly-scrunched aluminum foil, etc.).

So, I'm guessing that you'll need to bake the horns for at least an hour... even that long may not fully cure the innermost parts, but if you don't need the horns to last forever that won't be a problem (...what would eventually happen is that the inner parts would start dissolving the fully baked clay of the outer parts and make the outer parts sticky).

Baking the Sculpey brand that long would definitely darken it a lot, but presumably that won't be an issue since you're using black clay.  It still won't "burn" till the temp gets a lot higher.
(other brands don't darken as quickly as the Sculpeys... the least affected is Kato Polyclay, followed by FimoClassic, Premo, FimoSoft, and Cernit in no particular order).

I would definitely recommend that you use an accurate oven thermometer when baking the horns, and also buffer the temp around the horns by using some kind of "enclosed baking" method -- both to hopefully avoid any cracking and to just the keep the temp always-below 275.
The easiest way is just to bury the horns in a pile of baking soda or cornstarch (on top a cookie sheet or a glass baking dish, etc, for support), or you can put them in a lidded box or other things (there's more info on that on this page about doing that, and baking polymer clay in general:
http://www.glassattic.com/polymer/baking.htm
...click on Enclosed Baking...)

Re the cracking, I'd also try to cool the baked horns slowly (in the oven if possible).



Good luck!

Diane B.
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POLYMER CLAY "ENCYCLOPEDIA" 
http://glassattic.com/polymer/contents.htm
few of my photos
http://s96.photobucket.com/albums/l163/DianeBB
(had to move them from YahooPhotos, so many now without captions)
pookieb
« Reply #2 on: September 29, 2007 08:15:16 PM »

Thanks diane!  I went ahead and baked for an hour just on a pan with some parchment.  When I pulled them out I let them cool completely before i even looked at them crooked.  I plan on covering them with future floor polish and (maybe) rebaking.  I was wondering what your thoughts on that are.  I have looked at the site under the sealing section but there's of course no definitive answer.
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Diane B.
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« Reply #3 on: September 30, 2007 10:17:45 AM »

Glad to hear they didn't crack!

Quote
I plan on covering them with future floor polish and (maybe) rebaking.  I was wondering what your thoughts on that are.  I have looked at the site under the sealing section but there's of course no definitive answer.

The general advice for rebaking a polymer item with Future (or Varathane) on it, is to bake at no more than 250 for only 5-10 minutes.  That just makdes the acrylic feel "harder" and less slightly-tacky if it was (usually from humidity, or incomplete "drying" --which can actually take a week or so).


HTH,

Diane B.
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POLYMER CLAY "ENCYCLOPEDIA" 
http://glassattic.com/polymer/contents.htm
few of my photos
http://s96.photobucket.com/albums/l163/DianeBB
(had to move them from YahooPhotos, so many now without captions)
pookieb
« Reply #4 on: September 30, 2007 07:47:01 PM »

So it doesn't make the piece stronger to bake it like people have said?
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Diane B.
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« Reply #5 on: October 01, 2007 02:07:24 PM »

Quote
So it doesn't make the piece stronger to bake it like people have said?

That depends on which thing you're talking about.

Longer baking does make polymer clay stronger, but clear acrylics can't usually take longer baking, or quite as much heat as polymer clays generally use... if baked too long or hot, those can yellow (the ones without a UV protectant) or they can bubble, etc.  That's why re-baking (baking the finish on previously cured clay) is usually done at a slightly lower temperature and for less time.


Diane B.
« Last Edit: October 01, 2007 02:08:15 PM by Diane B. » THIS ROCKS   Logged

POLYMER CLAY "ENCYCLOPEDIA" 
http://glassattic.com/polymer/contents.htm
few of my photos
http://s96.photobucket.com/albums/l163/DianeBB
(had to move them from YahooPhotos, so many now without captions)
pookieb
« Reply #6 on: October 01, 2007 08:40:30 PM »

Thanks for everything, Diane!  You are the PC Encyclopedia.
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Diane B.
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GlassAttic --polymer clay "encyclopedia"


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« Reply #7 on: October 02, 2007 09:35:13 AM »

Actually, I should have added that you might have been confused because baking an acrylic finish will make it (that is, the finish) "harder," but that's not the same as baking longer to make the clay harder or stronger--except i perhaps right on its surface.


HTH,

Diane B.
THIS ROCKS   Logged

POLYMER CLAY "ENCYCLOPEDIA" 
http://glassattic.com/polymer/contents.htm
few of my photos
http://s96.photobucket.com/albums/l163/DianeBB
(had to move them from YahooPhotos, so many now without captions)
pookieb
« Reply #8 on: October 03, 2007 08:46:12 AM »

That's what I meant...baking the acrylic finish makes it harder.  I'm just letting it air dry though.  Trying to avoid noxious fumes today.
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