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barb9000

applying iron oxide to greenware

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Hi - new member and fairly new to ceramics - I am wondering if it is possible to use black iron oxide on greenware as a wash, without wiping away, and to bisque fire pieces this way. If so, how thin of a wash must I use?

 

Thank you

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The general answer is Yes. But I advise you to add a flux, maybe Frit 3124, 3110 to help . As to how much/thin to apply there are some questions: Which iron oxide are you using? What color clay are you using? What cone do you expect to fire? Higher temp will burn more of it out.

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You can use iron oxide easier as a wash on bisque if you are trying to accent texture.

The iron stays in the crevices after sponging over the surface. Using it at the greenware

stage would wash away the texture. Not sure what your goal is.

 

Marcia

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You can use iron oxide easier as a wash on bisque if you are trying to accent texture.

The iron stays in the crevices after sponging over the surface. Using it at the greenware

stage would wash away the texture. Not sure what your goal is.

 

Marcia

 

 

Marcia, I have sprayed iron oxide on heavily textured buff colored clays, and then lightly sanded them with a scruff pad to bring up the high areas. I spray because I do not want to soften the greenware texture with the brushing. This works well for a lot of things especially when using a light body underneath. Now I am trying the same thing with a darker body under, and a white slip over top.

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What the big difference with RIO. And. BIO. My RIO washes usually turn out black.

 

 

Red iron(III) oxide - Fe2O3

Black iron(II) oxide - FeO

 

At high temperatures, Fe2O3 starts to break down so O and F take off and you are left with the FeO

In oxidation, this is how you get those cool "oil spots" happening on the glaze where Fe2O3 is converting and free O drags F to the surface and leaves it there.

Someone can probably get you more detailed description of the process.

curt and mousey like this

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The general answer is Yes. But I advise you to add a flux, maybe Frit 3124, 3110 to help . As to how much/thin to apply there are some questions: Which iron oxide are you using? What color clay are you using? What cone do you expect to fire? Higher temp will burn more of it out.

Chris, why do you add flux and why frit? I thought iron oxide was a flux in itself. Would you use it whether it was greenware or bisk?

thanks david

 

 

 

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The general answer is Yes. But I advise you to add a flux, maybe Frit 3124, 3110 to help . As to how much/thin to apply there are some questions: Which iron oxide are you using? What color clay are you using? What cone do you expect to fire? Higher temp will burn more of it out.

 

Chris, why do you add flux and why frit? I thought iron oxide was a flux in itself. Would you use it whether it was greenware or bisk?

thanks david

 

 

 

 

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The general answer is Yes. But I advise you to add a flux, maybe Frit 3124, 3110 to help . As to how much/thin to apply there are some questions: Which iron oxide are you using? What color clay are you using? What cone do you expect to fire? Higher temp will burn more of it out.

 

 

hi Chris what happens if i do not use a flux or a frit to the oxide to my work and would it make a different if i was applying it to a bisque or green ware work????

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i am not a technical person, just one who goes by experience. you seem to have an underlying lack of knowledge about the whole process if you originally thought something would explode if you covered it in a wash. a wash as i define it is simply wet oxide you apply by some means to a pot whether green or bisque. the oxide alone will become dust if you handle it after the application. these people trying to help you are suggesting some way of preventing that dusting off of the pot and the color staying more firmly fixed in place.

 

what is it you are trying to do? if you can formulate the question you may get better answers.

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You can use iron oxide easier as a wash on bisque if you are trying to accent texture.

The iron stays in the crevices after sponging over the surface. Using it at the greenware

stage would wash away the texture. Not sure what your goal is.

 

Marcia

 

 

This is how, I've always used oxides. It's a great effect.

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I am using oxides (usually copper oxide/carbonate) to highlight some parts of my pots, by masking where I don't want this, and spraying the oxide solution lightly with an airbrush. I'm aiming for a subtle 'blush' within the transparent glaze. A few questions to help me perfect the process! I particularly want to avoid the oxides moving on to areas I want to remain white, and want a subtle effect overall.

 

- does it make any difference whether the oxide is under or over the transparent glaze?

- if it's under, can I fire it on, to prevent it moving when covered by the glaze?

- If so, what is the lowest temperature that will achieve this?

- alternatively, could I add the oxide to some of the transparent glaze (instead of using in wash form), spray or brush this, remove masking and spray over the whole piece - would the oxide still break through?

 

Any advice would be most welcome. Thank you.

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I've been using copper carb in a way that might answer some of your questions.  I mix the copper carb with a white terra sig just because its a handy way to stick the stuff, copper carb seems to wipe off a lot easier than RIO and mang.diox.  I apply this mix to a textured bisqued piece, then wipe it off the areas I want the base clay color to show then put my transparent over and glaze fire. This gives a nice green with a wide range of light and dark areas.  Adding the copper carb to the glaze directly gives a much more uniform look, less textured, so its not what I want.  It makes a nice green glaze if that's what you want though.  Some of the carb burns out so I don't worry about getting it all off.  Applying over the glaze seems to be a bit more irregular on what burns out. As I'm looking to emphasize the texture, this works much better.  A thicker layer of glaze = more movement of the color.  Sometimes I'll re-bisque to lock the copper carb on before glazing, sometimes not.  Its a time and patience thing!

 

post-14098-0-29155300-1387446351_thumb.jpg

 

Here I wiped almost all the copper carb off the raised surface and used a semi-transparent satin white over the copper carb. then went back in and added more carb on the lip of the pot.  

post-14098-0-29155300-1387446351_thumb.jpg

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Thanks Maryjane - that will be another series of tests for me

 

Texture isn't the thing with the particular pieces in question, but I do also do textured bowls, so I can store this up for the future!

 

Attached is a picture of one bisqued bowl which I have airbrushed with copper carbonate (was awaiting for advice before deciding whether to do a 2nd bisque before glazing!) so you can see what I'm on about and another finished piece with the effect I'm after (I made this way back and can't remember how I went about it!)

No idea why my photos turn round when attached - perhaps it's an ipad thing!post-13648-0-91808300-1387448180_thumb.jpgpost-13648-0-61199900-1387448197_thumb.jpg

post-13648-0-91808300-1387448180_thumb.jpg

post-13648-0-61199900-1387448197_thumb.jpg

Sallyd, Joe_L and ShellS like this

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I normally sponge or brush my glaze on, but I bet if you're spraying you'll be fine just going with the one bisque.  With brushing though, the copper carb was lifting, which is why I started using a terra sig base and often do the second bisque. You're just going to have to do some tests to see what the glaze/copper carb combination do.  

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Thanks for all the info, just one question not yet answered for me.

If I spray oxide on to bisque and want to refire to fix it before glazing - what temperature will fix it?

In the future I think I'll spray on to greenware, but currently I have a few pieces already bisqued & don't want the oxide to move at all.

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I don't think you need to add frit to an oxide you're using as a wash.

Firing it on a bisque to set it for glazing seems an extra step and will, yes keep it in place during the glazing process but not during the glaze firing, this would depend on the nature of hte glaze. Some people merely spray a starch or soft drink onto the area to set it before glazing without the extra firing.

On white bodies I prefer to put the oxide ono greenware as onto a bisque seems to colour the clay body.

But if scouring any dry clay use appropriate safety measures.

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 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:

teabowl_mordor_by_j_knez-d6glwvp.jpg

 

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:

jar_owl_small_brown_by_j_knez-d63em23.jp

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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.

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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!

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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.....

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