Jump to content


PeterH

Member Since 28 Apr 2013
Offline Last Active Today, 07:43 PM
-----

Posts I've Made

In Topic: Adding Stains To Terra Sigililata

Today, 05:12 PM

From a lost digitalfire entry captured by clayart at:

http://www.potters.o...ubject49916.htm

 

Vince Pitelka

I always like to work with pure clay terra sigs, because they give the best
shine. It is of course natural that others will want more color, but unless you
can ball-mill the mixture the shine will be reduced. At U-Mass we experimented
with both oxides and mason stains and got good results by ball-milling the
thickened evaporated terra sig and colorants for a day or so. I have used both
oxides and mason stains without ball-milling, and the shine is reduced
slightly, but the results are still satisfactory. [My emphasis.]

 


In Topic: Adding Stains To Terra Sigililata

Today, 06:33 AM

A word of warning, inspired by a post of Tyler's that seems to have gone.

 

From: http://claystore.alf...nd engobes).pdf

 

Cautionary note:

Many metal oxides are not food safe in slips (because slips lack the glassy structure found in glazes)
 
If its not safe in the raw state, chances are it won’t be safe in a fired slip either

 

The low-fire nature of terra-sig only emphasises the message.

 

PS A beautiful example of terra-sig used in non-functional smoke-resist raku.

I believe the terra-sig has added iron oxide, and was milled.

http://www.duncanros...mage_id=2&cat=2

 

For what it's worth you can buy very fine (~1μm) iron oxide as artists pigment -- at a price.

http://www.kremer-pi...ized-48289.html

Look for local distributor and/or check payment options. Years back I bought something

from them, and had to pay via my bank (with currency currency fee).
 


In Topic: Clear Glaze For Iron Oxide Stain

Today, 06:07 AM

If you are going to do some test tiles, you might try a soda wash on one to see how it looks.

http://community.cer...?hl=+soda +wash

 

 

Motivation.

 

This is using soda wash as a proxy for a  glaze that doesn't dissolve iron (e.g. Ca-free? [1]).

 

[1] Geysbeek, Red Glazes at high temperatures

Transactions of the American Ceramic Society, v1, pp 62-65 (1899)

Which is on pages 68-71 of the scanned copy at:

https://ia600302.us....actio01amer.pdf

 

A transparent version of these c8 gazes might be brought down c6 by adding boron.

But how do you get a calcium-free insoluble source of boron (without making your own frit)?


In Topic: Adding Stains To Terra Sigililata

Yesterday, 03:50 PM

In the UK, Mason stains aren't so easy to get

 

Scarva seem to offer them.
http://www.scarva.co...tains/c-43.aspx

 


In Topic: Paper Clay - I'm New To This...

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