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stains and oxides used to make coloured clay

updated tue 22 sep 98

 

David Hewitt on mon 21 sep 98

Do others have the same experience with body stains as detailed below?
I make a range of agateware pots in different colours. I use a porcelain
clay which gives the white colour. I mix 1Kg of the porcelain clay at a
time with a colouring oxide or body stain. Cobalt oxide for blue, chrome
oxide for green, B126 Tan Brown for brown, Blythe Strong Red for pink,
Sun Yellow for yellow. Around 70% to 80% of any agate piece that I make
is the white porcelain and the rest two other colours. The white with
the colours are 'assembled' before throwing. Ideally the white and the
coloured clay should have the same moisture content to avoid throwing
problems. The coloured clay when mixed is kept in plastic bags, but I
find that those using body stains as distinct from plain oxides become
harder (dry out more) with time, even though very well covered in
plastic. If I do not use all the coloured clay I have mixed, with Tan
Brown body stain for example, within a three week period it is likely
that I will have to soften it by adding some moisture before it can be
used for throwing when mixed with the other colours.
Does anyone else have a similar experience please? Also can anyone give
me an explanation as to why this should be so? What chemically /
physically is the difference between the plain oxide and a body stain
(presumably fritted) that should give rise to this?
For fuller details of how I make agateware you can, if you wish, look at
my web site and go to 'Pottery Techniques'. (incidently in view of the
recent thread on HTML, this site has been written using HoTMetalPro 3.0.
I find it quite easy to use, but make no recommendation as I have not
tried others).
David
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP6 1DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Own Web site http://www.dhpot.demon.co.uk
IMC Web site http://digitalfire.com/education/people/hewitt.htm