Jonathan Kaplan on thu 12 apr 01
on 4/11/01 8:11 PM, Burton Isenstein at bisens@ARTIC.EDU wrote:
> I am looking for a slip casting recipe for white earthenware. We
> already use a red earthenware casting body that we fire to bisque 04
> and glaze 06.
> I need a body that works in the same temperature range and is
> compatable with commercial underglazes and glazes. I use Darvan as
> defloc and would like to do the same. Is 50 OM4/50 talc adequate?
> Would Darvan percentage be the same for my redart formula as white
> earthenware? Please e mail response directly. Thanks a bunch!
Basically, you are on the right track, with some modifications.
However, I would not use OM 4 as it is one of the dirtiest ball clays out
there and has relatively poor deflocculation abilities.
Rather use FC 340 from Old Hickory Clay Co (Fast Cast 340) that has been
specifically been designed for casting purposes.
As Red Art has a quite fine particle size, you may want to add some
Velvacast to the mix. Keep the ratio of plastic materials to non-plastic
materials at 50/50 and you can arrive at some excellent casting bodies. The
talc at 50% may need to be slightly lessened as the Red Art is quite an
active flux also. You could fill in the balance with Pyrophyllite for
instance:
Red Art 15
VelvaCast 10
FC-340 25
Talc 35
Pyrophyllite 15
total 100
and then add a VERY small % of barium (READ VERY SMALL) like 1/4% to
counteract the scumming of the red clays but not enought barium to
neutralize the organics in the slip that would render the gelling useless.
I would suggest that you also use Darvan 811 which is a sodium polyacrylate
better suited for use with iron bearing slips.
Post me off the list if you have any further questions.
Jonathan
--
Jonathan Kaplan
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
infor@ceramicdesigngroup.net www.ceramicdesigngroup.net
(use PO BOX for all USPS correspondence)
Plant Location
1280 13th Street
Steamboat Springs CO 80487
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