Gaynor Reeve on fri 23 oct 98
Does anyone know of a thick slip that I can spread 'THICKLY' onto dry or
even biscuit fired pots.
Right now I'm trying
RECIPE 1 RECIPE 2
30 hyplas 50 hyplas
30 china clay 20 china clay
15 potash feldspar 20 potash feldspar
11 borax frit 10 filnt
But the slip is cracking and lifting off the dry pot. I've always painted
thin coloured slips onto my biscuit fired pots and slabs with success, but
now I want to introduce lots of texture to my pieces. Is this possible!!!!
I'm firing to 1180c
Any suggestions much appreciated
GAYNOR REEVE
Ceramic Artist
email: gaynor_reeve@geocities.com
http://www.geocities.com/SoHo/Cafe/9125
Donn Buchfinck on sat 24 oct 98
No
a thick slip is tough enough to apply to a wet pot or surface and keep it from
cracking.
I have seen someone mix a teaspoon of calgon into a cup of water and add that
to the slip make the slip real dry not a lot of water then add some of the
calgon, the defloculates it. Water in the slip is what makes it shrink, and
a thick slip will crack.
as with a clay body the trick is to understand the drying qualities of a clay,
in what I have seen in the drying of clay there are two shrinks that occur
between wet to bone dry, the plastic and the non-plastic, cracks occur in the
non-plastic stage. This is when the pot rips itself apart, and this is why we
put sand or grog into the clay to help lessen the non-plastic shrink.
I cannot see a thick slip going on a bone dry surface or a bisque ware, and if
someone has gotten it to work then I would really be interested in hearing
about it
Donn Buchfinck
Valeree Bennett on mon 26 oct 98
Try using slurry from your claybody (with colorants, if
desired, or just plain with underglazes, etc.on top) on
leather hard pieces--it usually doesn't have a problem
sticking, and I've always had luck with it. As for bisque,
I'm not sure it's possible...I've seen many nasty blowouts
due to thick slip on greenware as well as bisque.
Good luck
Valeree Bennett
vsbennet@bellsouth.net
Craig Martell on mon 26 oct 98
Hi:
You can make slips for bone dry and bisque pots by reducing the plastics in
the slip or by a combination of plastic(clay) reduction and using clays that
have lower plastic shrinkage rates. Kaolin would be a better choice than
ball clays for bisque slips because ball clays have a higher shrinkage rate
in the hydrated state. In porcelain or white slips you could also add some
very fine mesh molochite to cut the shrinkage and keep the spar and silica
within limits. You will probably be approaching an engobe when you find
something that works.
Porcelain slips are usually about 50% clay and 25% of spar and 25% silica.
Lower the kaolin content and raise the spar and silica accordingly, while
keeping the same proportion of spar and silica. At some point, you will
find a slip that will work. I can't give you a receipe because I don't know
what your claybody is like and it's best that you work this out to your own
satisfaction.
I regularly apply porcelain slips made from the same formula as my throwing
body to bisque pots. I spray the slip on and usually can get 1/16 to 1/8th
inch thick without any problems. I usually apply slips at the leather hard
stage but I'll succumb to afterthoughts once in a while and apply them to
bisque ware. A certain amount of moisture is lost from the slip during
spraying and I think that this helps avoid problems. I've trailed on thick
lines to bisque ware too and it's worked fine. I guess it just depends on
what you do and how you do it sometimes. I was told in school that you
shouldn't apply slip to dry and bisque pots. Good advice, but I would also
advocate breaking the rules. Try stuff and see what happens.
regards, Craig Martell in Oregon
Stephen Mills on mon 26 oct 98
In message , Gaynor Reeve writes
>----------------------------Original message----------------------------
>Does anyone know of a thick slip that I can spread 'THICKLY' onto dry or
>even biscuit fired pots.
>Right now I'm trying
>
> RECIPE 1 RECIPE 2
> 30 hyplas 50 hyplas
> 30 china clay 20 china clay
> 15 potash feldspar 20 potash feldspar
> 11 borax frit 10 filnt
>
>But the slip is cracking and lifting off the dry pot. I've always painted
>thin coloured slips onto my biscuit fired pots and slabs with success, but
>now I want to introduce lots of texture to my pieces. Is this possible!!!!
>I'm firing to 1180c
>
>Any suggestions much appreciated
>
>
>GAYNOR REEVE
>Ceramic Artist
>email: gaynor_reeve@geocities.com
>http://www.geocities.com/SoHo/Cafe/9125
>
Try these two, they are for use on biscuit ware/tiles. Measurements are
parts by weight, consequently they don't add up neatly to 100, but they
work.
Stoneware:
calcined china clay....50
hyplas 71 ball clay....50
potash feldspar........90
calcium borate fritt...10
(firm and dryish)
Earthenware:
ball clay .............15
china clay.............15
calcined china clay....20
calcium borate fritt...20
talc...................15
flint..................20
zirconium silicate.....5
Steve
Bath
UK
--
Steve Mills
Bath
UK
home e-mail: stevemills@mudslinger.demon.co.uk
work e-mail: stevemills@bathpotters.demon.co.uk
own website: http://www.mudslinger.demon.co.uk
BPS website: http://www.bathpotters.demon.co.uk
Ron Roy on mon 26 oct 98
Hi Gaynor,
Try deflocculating your slip. Deflocculated slips need much less water to
flow and therefore don't shrink as much. If that won't work sub some
calcined clay to cut shrinkage - and deflocculate. You can also add some
bentonite - this sounds contrary but - china clays are weak while drying -
you can get some higher modulus of rupture with ball clay and/or bentonite.
>----------------------------Original message----------------------------
>Does anyone know of a thick slip that I can spread 'THICKLY' onto dry or
>even biscuit fired pots.
>Right now I'm trying
>
> RECIPE 1 RECIPE 2
> 30 hyplas 50 hyplas
> 30 china clay 20 china clay
> 15 potash feldspar 20 potash feldspar
> 11 borax frit 10 filnt
>
>But the slip is cracking and lifting off the dry pot. I've always painted
>thin coloured slips onto my biscuit fired pots and slabs with success, but
>now I want to introduce lots of texture to my pieces. Is this possible!!!!
>I'm firing to 1180c
>
>Any suggestions much appreciated
>
>
>GAYNOR REEVE
>Ceramic Artist
>email: gaynor_reeve@geocities.com
>http://www.geocities.com/SoHo/Cafe/9125
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
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