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applying iron oxide to greenware

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#21 Rebel_Rocker


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Posted 30 July 2014 - 06:13 PM

 Not sure what temp it takes to 'fix' the oxide.


 Main problem with brushing it on is that it can be 'spotty'. That can be good or bad. One time I wanted it heavy so I put it on greenware, bisqued and then reapplied on the bisque. It did come out heavier than usual (on bisque only). My intent was a very metallic no glaze finish.


 This was just applied haevily to bisque:



Putting it on greenware helps it fix some, but it can still be rubbed off. So the temp required for a full fix is higher than cone 6.


 This was put on bisque then rubbed off with sponge just to highlight:


#22 Celia UK

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Posted 31 July 2014 - 02:08 AM

Thanks Babs and Rebel Rocker - helpful suggestions all round! I've gone for 1000oC re-bisque this time as I know it's worked in the past. Good tip on spray starch Babs, I'll get some in in case I need to do this sometime in the future! Happy potting everyone.

#23 Babs


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Posted 31 July 2014 - 04:44 AM

When it's not so pressing, have a try at a few ways.

Good luck.


#24 weeble


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Posted 31 July 2014 - 03:43 PM

I've tried RIO, manganese dioxide, and copper carb on greenware.  They all brush off pretty easily after a cone 05 bisque without something to fix them. The terra sigillata is a very fine slip, and it acts to fix the oxides so they DON'T brush off at bisque, so you can brush glaze over very easily.  The copper carb was brushing off bisque very easily too, so I usually use the copper carb/terra sig mix on bisque as well as green.  RIO and manganese dioxide however you can simply apply to bisque and rub it back with a sponge, it sticks well enough to get fun effects!


HMMMMmmm, wait, its been ages since I started using the sigs with stuff on greenware, so maybe it was something else I was doing that was giving me fits. I just know I started using the sig and things started working!  It might have been the Mason stains that I was trying to use on the greenware that were the problem, I normally use RIO and manganese straight, but only on bisqued stuff, and the copper carb was NOT behaving as well on the bisque.  Mason stain with the sig works wonderful on greenware though.


Sigh, ok, disregard that first part, I'm a tad burnt out trying to get ready for a show!

Maryjane Carlson

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#25 Celia UK

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Posted 31 July 2014 - 04:44 PM

That's really surprising Maryjane - applied to bisque and refired to cone 06 these are all fixed on my white earthenware. I had to scrub a textured area really hard with sand paper then a stiff brush, this morning, to remove just a little manganese dioxide where it was heavier than I wanted. I can then dip without any contaminating the bucket of glaze. I wonder why there's a difference between applying it to greenware and bisque? Perhaps some of the chemists out there have the answer.
I had a call this morning from a local professional potter working with earthenware who said cone 016 (750 oC) would be high enough for refiring copper carbonate on bisque, but I haven't tried this and another time I'll be applying it to greenware.
Curiouser and curiouser.....

#26 Pots by Char

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Posted 01 August 2014 - 12:34 PM

I apply dry greenware for a soft subtle color...bisque fire then glaze with a clear glaze and glaze fire.  I found if I applied to the bisque and applied glaze over it.  The glaze seemed to wash out the oxide somewhat, and since this is a subtle effect anyhow it left it pretty washed out indeed.  So now I do the oxides on  the greenware and the bisque firing sets the subtle coloring into the clay.  I do not wipe them off though, Just gently brush on the oxide and it settles darker in the cracks and crevices of the pieces quite naturally..leaving the smooth areas much lighter.

#27 Mayapur



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Posted 31 October 2015 - 12:58 AM

I was hoping that I could use the red iron oxide mixed with only water on greenware to just add simple decoration to planters that I am firing to 1080 Celcius. Thought that it would melt onto the pot like a glaze. Is there a way to do this, or do I need to mix it with clear glaze for it to stick?

#28 Celia UK

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Posted 31 October 2015 - 08:32 AM

My experience says it will 'stick' with firing to 1080oC, but I don't know if the colour would last indefinitely. For copper and cobalt oxides, if you want the greens and blues they definitely need a glaze on top. If you're just after black it may be ok without. An underglaze of the final colour you're after will do the job without glazing over. These contain the flux and some clay, so they do bond to the surface. Someone here will be able to advise I'm sure.

#29 High Bridge Pottery

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Posted 31 October 2015 - 08:58 AM

I think the general consensus when using raw oxides to paint on is to mix them 50/50 with a frit. Adding some clay would help stop it dusting off the pot before fired if that becomes an issue.


This will still not be glassy/glossy but will have the metallic sheen. Over cone6 you can just use it 'as is' I think.

One physical test is worth a thousand expert opinions.


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#30 MatthewV



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Posted 13 November 2015 - 01:03 AM

An iron oxide decoration fired to 1080°C would show for many years on a planter. Think about this: the pink-red color of planters is also coming from iron.

Cobalt and copper would last for awhile.


I personally apply oxides on leather hard pieces and bisqueware. Time consuming patterns get a second bisque. I almost always put glazes over (transparent but not clear usually). I don't work on greenware-- too fragile and too absorbant.

I mix my oxides with china clay. So I am really using an oxide laden slip. This help reduce globs from blistering and generally makes brushed application easier.

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#31 OldUberGoober



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Posted 13 November 2015 - 11:39 AM

Consensus among the potters I hang with is to add some fine white clay (EPK is usually handy) to the oxide wash for C10, and I've had good results at C6.  it does settle quickly, as I'm sure frit would, but I just realized I've never flocculated it, and that will be the subject of tonight's experiment.  Epsom salts is our friend!


BTW, Iron Chromate seems to yield a nice chocolate brown, less red than the various iron oxides.

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