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#110978 What Clay To Use To Make Waterfall For Cat And How To Use Clay?

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.

#110977 Mixed My A First Batch Of Glaze

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


#110226 Relay / Magnetic Contactor Question

Posted by PeterH on 17 July 2016 - 06:03 PM

A long shot, but a firm called "Kilns and Furnaces" exists in the UK.




Might be worth a query.

#109823 Rare Earth Oxides

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.

#109563 Ian Currie Test Tiles Forums?

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.

#109525 Mocha Diffusion

Posted by PeterH on 28 June 2016 - 08:33 AM

That was my problem too, the few times I tried.


Just looked up a few utube videos on mocha diffusion, it's a surprise just how fast they seem to work

(assuming that the videos are uncut and in real-time).


Less than 30secs from bucket to completion on this one


Usability seems to stop after 10secs on this one



I'm truly uncertain how deflocculating the slip will effect things "chemically", but given the mildly acidic

nature of most mocha teas I suspect that soda ash will. Also deflocculation means that you have more

"clay" for a given viscosity, which might effect the drying time of the slip.


One of Robin's slips is given in:


Various slip recipes are good, the most important ingredient being a high
percentage of ball clay.  A basic recipe which will fit most bodies and
which can easily be colored with stains or various oxides would be;  
I have taught this process all over the world and you can use any ball clay,
any feldspar, any kaolin and any 200 mesh silica, flint or quartz.  They will
all work. This slip is good on most clay bodies from cone 04 to 12,  in any
atmosphere. The thickness should be like double cream, or room temperature
10 W 30 motor oil. A liquified porcelain clay slip will not usually work well
since a porcelain body usually contains a maximum of 50% plastic clay material,
the remainder being non-plastic fluxes and fillers such as feldspars and silica.




PS if only for for the humour:


Peter Linford on thu 22 jul 99
Hi Martin,
I too used to mix up disgusting fluids till one day washing brushes
discovered that a mix of oxide and washing up liquid works just as well and
the brushes are really easy to clean.
hope this will help
Peter in Wakefield, Yorkshire.



#108147 Weight Difference Between Commercial Plates And Handmade Plates

Posted by PeterH on 04 June 2016 - 01:25 PM

A Digitalfire article provides an interesting footnote to John's comments on 'Modulus of Rupture'.


The MOR of two bodies was measured unglazed and with five versions of a Butter Matte glaze.

porcelain unglazed=9122 glazed from=5597 to=3811

stoneware unglazed=3955 glazed from=8135 to=3930



#107690 Longterm Glaze Issues | Sometimes Runny, Sometimes Breaks The Pots

Posted by PeterH on 28 May 2016 - 09:07 AM

All this seems to be drifting well away from the interests of the original poster, and might be better placed in a separate thread.

IMHO it's very speculative silicate-melt theory. 


>So all you have to do is look at the first ionization energy for each element to determine how quickly it will lose its first orbital atom.

[I assume that is a typo for 'how easily an atom loses its first electron'.]


Absolutely true, but to take an example: the sodium atoms in the nepheline syenite became sodium ions before they

were incorporated into the nepheline syenite crystal (after all it is an ionic crystal). That's probably millions of years ago.


>We call it the melt temp in glaze, but in reality it is when it loses it first atom (donor/ reductant/oxidation).

[I assume that is a typo for 'when the atom loses its first electron'.]


Err, I don't think so. The sodium in the nepheline syenite starts out as Na+ and stays like that through any melting process.

I would suggest that most atoms in a glaze don't change their level of ionisation from that in the raw ingredients.

[There are obviously a few exceptions, mostly involving transition metals.]

  • Min likes this

#107064 Has Anyone Actually Made Pavers?

Posted by PeterH on 17 May 2016 - 10:37 AM

FYI this was recently posted on Clayart, it seems relevant to sculptures, not certain about pavers.


There's excellent information on claybodies for outdoor hard-freeze environments in Val Cushing's handbook. He gets pretty technical in terms of figuring how suitable a particular claybody might be, but the basics make sense. It did surprise me when I found out about this, because initially seemed counterintuitive. You don't want to use a highfire claybody unless it is 0% absorption, which is hard to achieve. The problem with most highfire bodies is that there is still some absorption, and over time the water absorbs, and then in a hard freeze it can't get out and the piece cracks or spalls. That's the same reason it's so dangerous to refire a piece that has been in regular daily use in contact with water. The moisture has impacted into the piece and can't escape in the firing, and the piece can explode with enough force to destroy everything else in the kiln and even the kiln itself. I have seen this happen.

Most of the architectural terracotta decorating the exterior of so many buildings in New England and across the Midwest was fired to low-midrange - around cone 2 or 3. The idea is to have enough porosity to allow the pressure of freezing water to escape, but enough mechanical strength to keep the pressure from fracturing the clay, and the right terracotta body fired to low-midrange does that. Regular lowfire bodies are of course very porous with inadequate mechanical strength, and we've all seen examples of lowfire pots, sculpture, or tiles left outdoors in hard-freeze climates, where the surface starts to spall off and eventually the piece just disintegrates.
- Vince

Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
[email protected]

#106897 Luster

Posted by PeterH on 14 May 2016 - 03:37 PM

I remember reading an article which emphasised the advantage of resist techniques for resinate lustres.

You spend most of your time and effort handling resists, and minimal time actually applying lustre.


... found it, the quote was:

This focus will be on the resist technique which I use so as to limit my exposure to lustre; 90% of

my time with lustre is spent in applying inert resist and only 10% in actually applying the lustre.



#102296 White Glaze

Posted by PeterH on 20 February 2016 - 07:16 AM

This is my first official time at making a glaze from scratch. Its a simple white glaze from a Lucie Rie recipe, fired to ^6 oxidation

I associate Lucie Rie with a time long before ^6 became popular. Are you sure that this glaze is intended for ^6?



Had a quick look and found this posting, suggesting a significantly higher firing temperature.

Also note the possibility of crawling when used on bisc.



Miri, I share your love for Lucie Rie's work. I have one recipe (copied long ago from a UK ceramics book but never used) attributed to her. Here is the text (verbatim with commentary) from the book:

Lucie Rie's White (oxidized, 1,250°C)

58 soda feldspar
14 china clay
10 zinc oxide
10 tin oxide
8 whiting
8 flint

This glaze is the famous glossy white glaze used on Lucie Rie's tableware, often stained brown with manganese and copper carbonate on the rims. It can be tried with less tin - 5 or even 2 percent - but is expensive to make, and inclined to crawl when used on biscuit ware, perhaps because of the high zinc content. Lucie Rie's pots, of course, are once fired, which avoids this problem.

#101784 Paper Clay - I'm New To This...

Posted by PeterH on 10 February 2016 - 05:50 PM

Do be warned, it stinks in a new and fascinating way after about 2 weeks when the fibre begins to rot. Make only as much as you need at a go. People will advise you to add a capful of bleach to prevent this, but it only delays the inevitable.


While Diesel's warning is true, all is not lost. Cannot find the original ref, but here

is my memory of it from a 2009 clayart posting.


Many years ago I read a letter in one of the ceramic mags from a potter who developed a

chronic farmer's lung condition, apparently from mould spores given off from "off" paperclay.

So it's not something you want to have around year-on-year.

His solution was very simple, just drying the paperclay into ingots (prob.in a plaster mould).
He reconstituted the nextday's clay in a bowl with a measured amount of water in it. The great

wicking you get from the paper fibre ensured that it was usable by the next day, maybe sooner.

Regards, Peter


#100564 Mishima: Incised Through Wax Resist Or Scraped?

Posted by PeterH on 24 January 2016 - 06:11 PM

If I'm not mistaken, CAD has an article about a ceramist who incises, bisques, and then inlays.  I couldn't find the article earlier, but I'm 99.9% positive it exists and that it's something from this site.


Rings a bell. The one I remember is:


#99756 What Kind Of Relays Do You Use In Electric Kilns?

Posted by PeterH on 15 January 2016 - 09:59 AM

So I have two lines one at +120v and one at -120v that swap about?

Location Newcastle Upon Tyne. England


neilestrick: All that said, kilns in England may be different.


Single-phase UK is [almost] invariably 240V [ish] neutral and live. Although 2-pole switches are a very good thing,

especially considering how close your hands get to the coils.


PS UK neural should be safe, but mis-wiring, wiring failures and unexpected funnies can prevent this.

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#99586 Spodumene

Posted by PeterH on 14 January 2016 - 07:47 AM

Passed on in case you have bubble-trouble with a high-spodumene glaze.



Some types of spodumene do contribute to the formation of bubbles in the

glaze slurry. You can wash spodumene before use to alleviate this issue

(mix it well in plenty of hot water, allow to settle overnight, pour off the water

the next day and dry it).