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applying iron oxide to greenware


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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.

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  • 1 year later...

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?

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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.

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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.

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  • 2 weeks later...

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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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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  • 4 years later...

I have not yet found any clear glaze that could go over red iron oxide. Even zinc free clear glazes turn RIO white.  I have tried multiple suggestions for getting some shine or gloss on my iron oxide pieces so they don’t look so raw.  Ive asked many people if they know a flux or a frit that can be added to red iron oxide but have never gotten an answer that wasn’t speculative.  Someone commented in the above thread with suggestions of frit or flux, but later when someone else asked about this, he never replied.  I have tried using underglaze that looks similar to iron oxide, such as the mahogany colored Amaco underglaze but that doesn’t have the look I want and I don’t want it to be so shiny. Anybody out there have a solution?

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@Olinda Hi and welcome back!

Some of the reasons for the speculative answers are simply that you have to test things with the materials you have with your specific clay and your specific firing circumstances. Another reason is that a lot of things could work in a situation like this, and you may just have to pick one and try it. I know these answers can be maddening, so let’s try and narrow some things down.

I personally have had clear glazes crawl off an iron oxide wash cut only with water and no flux, I’ve had it turn green or various ugly/undesired things, but I’ve never had it go white. 
Can you give us an example of the look you’re going for and describe more precisely what you’ve tried? What temperature are you firing to and what clay are you using? Oxidation or reduction? What glazes have you tried? Are you mixing your own or using store bought? How thick have you put your wash on, and what fluxes or other things have you added to your mix?

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 @Olinda, are you looking to have the iron colour on a glazed piece or is it for non functional but you want a bit of shine to the iron?

20 hours ago, Olinda said:

I have tried multiple suggestions for getting some shine or gloss on my iron oxide pieces so they don’t look so raw.  Ive asked many people if they know a flux or a frit that can be added to red iron oxide but have never gotten an answer that wasn’t speculative.

If you're looking for something to add to the iron for a non glazed finish you can mix iron oxide with gerstley borate. I've used it up to cone 6 as 50 red iron oxide plus 50 gerstley borate. There is shine to it at this ratio. If you want it less shiny then decrease the gerstley borate, try it with 50 iron and 10 / 20 / 30 gerstley. (don't use the 50:50 version on the bottom of a pot, it's fluxed enough to stick to the kiln shelf)

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  • 1 month later...

 @Olinda,

Keep in mind that iron in your water supply produces stains on glazed porcelain (aka tubs, sinks, and showers) that are extremely difficult to remove without some chemical assistance.  

Try it and see what happens.  Adding a little sodium silicate to the iron oxide and water might help when the water evaporates; the sodium silicate becomes "water glass" which was used to seal flues on stoves  before more modern 'stuff' was marketed.  

LT 
 

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in reading this entire thread, i realized that the original post came from someone who was only on the forum for that one question and one day only.

that original ? was in 2013.   and the latest in 2020.  seems like a subject someone might write an article about for ceramics monthly.

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