Page 10 of this document might be relevant
Might be the kiln sitter manual at
I would wait for Neil's word on it, but I suspect that the sitter can switch more power than the kiln takes.
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Posted by PeterH on 01 December 2016 - 01:12 PM
Posted by PeterH on 10 November 2016 - 07:55 AM
This might be of relevance.
Added: Remembering the rather squat jar in the illustration, I was going to add that I would use a slimmer one.
Rereading the pdf, they say just that: A tall slender jar is best.
Posted by PeterH on 17 September 2016 - 05:25 AM
... as I was saying.
I cannot think of any obvious yellow pigment that might be involved, although I do feel that
iron might well be involved somewhere.
Looking at the differences between bar 4 and bar 5.
MgO down 1.-7 -> 0.55, Fe stable 0.17 -> 0.16, TiO2 up 0.03 -> 1.06
Which sort of argues for Ti involvement.
Well TiFe2O5 (pseudobrookite) is certainly yellow enough, as seen in "marbled terra sigillata"
... I would love to hear of any other slip or glaze that uses pseudobrookite as a colourant, and
the conditions under which it can be reliably produced.
It would be nice if the colourant was an Mg compound. Magnesium ferrite (MgFe2O4) is a potential
candidate, but I've usually seen it mentioned as a reddish brown colour:
- as an oil colour
- as an iron-red glaze
Although the colour is described as "presenting a yellow-orange color" here:
Anybody have any thoughts on candidate yellow pigments, and why it only appears in one of the test bars?
Added: This paper suggests that getting pseudobrookite to work as a yellow ceramic pigment isn't that easy,
with a tendency to produce browns.
Posted by PeterH on 06 September 2016 - 05:25 AM
Not intended as an answer, just adding to the discussion.
A vague memory of the term Tamman temperature lead me to this:
minimum cone for sintering cone 10 glazes
... which implies the idea of sintering may -- for some glazes at least -- not be the really great idea it sounds.
I have found that there is considerable difference in the way
different glazes act to sintering, Some harden up and stick well at
cone 04. Others want to fall off in sheets. Shinos did not work at
all and I decided to put them on at the kiln site.
I have had the same experience. I don't think 04 will
help. A sintered glaze can be more fragile than an unsintered
CMC is probably your best bet (maybe too late now.)
I does make a suggestion which you might prefer to adding gums to the glaze:
Subject got me wondering - could one spray the surface with a cheap fabric
spray starch to keep from damaging the glazed surface?
PS Do you have any bentonite in your glaze?
Posted by PeterH on 04 September 2016 - 07:00 AM
I'm unclear what range of colours you are trying to achieve. You might try asking a similar question on
a china-painting group as they would probably be more familiar with the problems of colour-mixing a
large range of colours "on demand" from a small palette.
AFAIK the people trying really hard to mix ceramic colours from a limited set of "primaries" are the
developers of colour printing systems (for producing transfers and even direct printing on clay). My
understanding is that they use a CMYK colour model. AFAIK such pigments are not generally/cheaply
If you are unfamiliar with cyan-magenta-yellow colour mixing, here is an example with oil paints:
Colours good for this sort of mixing are often called names like process-blue, process-red and process yellow.
Posted by PeterH on 03 September 2016 - 04:32 AM
You really can’t sub a feldspar (the minspar you used if I read your post correctly) and bentonite for the deflocculants that were called for. The soda ash with sodium silicate work together to deflocculate the casting slip.
As Min said.
(Also Digitalfire advises Do not put bentonite in the casting version of this body, the casting rate will slow down dramatically.)
The amazing differences in the property of slips with different level of flocculation can be seen in
a couple of John Britt videos:
... as these videos are not aimed at a slip-casting audience I would just take the message that
control of the state of [de]flocculation is important. Then I would re-read the article Min mentioned.
Here is another article which discusses deflocculating a slip (using a different deflocculant) which
highlights the problems of deflocculating just enough but not too much.
Go with Digitalfire's recipe as a starting point, and get both the density and viscosity in the right ball-park.
Then try glaze-tests again, as there is no guarantee that this will have fixed you problem .
If you still have shivering problems, there are [at least] two course of action you might try.
1) Tweaking Digitalfire's recipe, some possibilities are:
1a) Switching to a different ball-clay, or a mixture of ball-clays (I have no suggestions here).
1b) Invert Digitalfire's advice for crazing -- If crazing is a perennial problem, then use more talc
and less ball clay -- by using more ball-clay and less talc.
2) Start another thread asking for recipes for a cone 04 - 05 casting slip.
Posted by PeterH on 01 September 2016 - 07:20 AM
Do you have a ball-park figure for how much vinegar you are adding? (I'm interesting in working out
the final carbonate:acetate ratio).
Are you familiar with drop moulds, they might minimise surface disturbances when forming (fun to use too).
Posted by PeterH on 04 August 2016 - 09:32 PM
We bought a waterfall to encourage our diabetic cat to drink more water. A couple of lessons learned:
If you are in a hard-water area pre-boil the water or you will spend forever removing "tide-marks".
You will get hairs in the water that will finish up blocking the pumps filter (nasty to clean too). Much better
to enclose the pump in a fine-mesh plastic bag to catch the fur.
But it was a great success, and gave him a few extra months.
Posted by PeterH on 04 August 2016 - 09:25 PM
This makes my preferred specific gravity for this particular glaze 1.5?
Yes, you've got it. ... I admire your choice of example numbers to simplify the arithmetic.
PS You can always cheat and put (140-20)/(100-20) into google, it gives me (140 - 20) / (100 - 20) = 1.5
Posted by PeterH on 07 July 2016 - 03:04 PM
What kinds of places stock the lanthanides?
As a fellow UK resident, you might try asking http://www.ctmpotterssupplies.co.uk
I managed to get some cerium from them after it ceased to be in their catalogue. IIRC they
are associated with a company that sells more exotic stuff.
.... From their colouring oxides page
We are happy to supply companies with raw materials for other uses and, in fact, our parent
company specializes in metal compounds and rare earths such as cerium oxide, cobalt oxide,
cobalt carbonate, copper oxide, cuprous and cupric, copper carbonate, erbium oxide, iron chromite,
lithium carbonate powder and crystalline, manganese carbonate, manganese dioxide, neodymium
oxide, nickel oxide, praseodymium oxide, tin oxide, vanadium pentoxide etc and so we can usually
offer a good price for small and medium lots of these and many other materials; for larger lots we
will liaise with our parent company for you.
Edit: put quote in italics.
Posted by PeterH on 28 June 2016 - 04:11 PM
Don't know if this is of any interest/help but I remember an old J. Am. Ceramic Soc. article on silicon
carbide reduction. Among other methods they added SiC into a slip which they bisqued before
applying the glaze. Seems that the SiC only decomposed when it was wetted by the molten glaze.
It might be one way of getting uniform SiC action for all the sub-tiles on a full-tile, and using the same
glaze batches on several full-tiles with different SiC content in the slips.
... But harder to use dancing men, etc.
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