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speckled effect - questions


Mai
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Hi everyone! 

I'm new in the glazing area and I've a couple of questions :)

I'd like to create this (attached) style of colour (speckled effect) and according to my research I found several ways to get to that:

A. With Rutile 

B. With Ilmenite

C. With Iron oxide

D. With Manganese
 

My questions are:
 

1. Can I add any of these directly to the clay before throwing or do I need to add them to the glaze? (I read that Rutile and Ilmenite decant so you need to be mixing constantly)

2. In case I need/can add them to the glaze, can I do it to any white bought glaze (powder)? (I fire in low temperature)

3. What is the effects difference between these options? 

 

Oh! I almost forget, I also saw someone using steel wool (he fire it and use the dust of it to make this effect) Did anyone of you tried it before? Would it work in low temp (1000 Celcius)?

Thank you SO much!

Mai


 

IMG_22241-1024x768.jpg

Edited by Mai
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Hi Mai and welcome to the forum!

Your example looks like the maker used a glaze containing a speckling material rather than a speckled clay, you can see where there is a heavier concentration of speckles on the inside of the cup. This would happen if the glaze was thicker from dipping the pot and having a thicker glaze where it was poured out. My thought is the example cup has granular rutile added to an opaque white glaze.

Rutile contains up to 15% contaminants such as iron, tantalum, niobium, chromium and tin and is considered an impure form of titanium. Ilmenite has far more iron in it than rutile, approx 1/2 iron and 1/2 titanium. So ilmenite will give a darker speckle than granular rutile. What ever speckling material you use the amount of fines it contains will have an effect on the colour of the base glaze. Both iron and manganese are also going to effect the base colour of the glaze, some irons agglomerate more so than others giving larger speckles. If you find your speckling material has a lot of fines you could put it through a screen and just use the larger particles but this won't work with iron (because it agglomerates). (wear a P100 mask whenever working with dry materials and work outside if you don't have adequate ventilation)

To answer your questions, 

1 - You could do it either way but it's going to be far more cost and labour effective to add your chosen speckling material to the glaze rather than the clay.

2 - Have to try it and see. Start off with a weighed amount of glaze, if you use 100 grams of dry glaze add 0.3 grams of whatever speckling material you are testing. Mix it up then dip a test tile with an overlap so you can see what 1 vs 2 layers looks like. Now add another 0.3 grams of speckling material and repeat. Keep doing this until you have a total of 1.8 grams added to the test. It's not going to be super accurate since every time you dip a tile you are removing some of the glaze but it will get you in the ballpark.  

3 - See #1

Edited by Min
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I have tried to speckle clay with ilmenite and iron oxide, have never been able to notice with ilmenite. And iron oxide can work, but in reduction firing only.  Granular manganese is what speckled cone 6 bodies use in the clay, and it works very well.  Ilmenite in the glaze looks like your photo.

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Than you so much @Min & @liambesaw
Im going to play this week with Ilmenite, iron oxide and manganese and I'll let you know how it went :)

I was also recommended to play with ashes to get this kind of effects Ill send pics.

 

@Min, thank you so much for taking the time and giving such an extensive reply. It is really useful and motivating! I really appreciate it! :)

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It's not just any mask you need to wear when working with glaze chemicals, it needs to be one that is rated as P100 like this one. There is an article here by Monona Rossol explaining the differences between the different mask ratings and why masks are necessary. Dust particles from the materials used can hang around (unseen to us) for a few days, best to work outside wearing a mask to keep the dust out of your work area. Fumes from manganese when firing the kiln must be avoided, if your kiln has a vent make sure it's working well before firing glazes or claybodies containing it. If your kiln is outside then avoid the area it's in until the kiln has finished firing.

The speckle material you add to the glaze won't make a microwave safe cup not suitable for the microwave but by using earthenware it probably won't be suitable for using in it. Unless the glaze 100% seals the surface with no crazing, micro fissures or pits then moisture will inevitably get into the clay over time. When that moisture turns to steam in the microwave you can have problems.

Edited by Min
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So how do people get this effect on mugs, plates, etc. that you can actually use as china? Like this kind... 

Im trying to research (even asking people in Instagram) but it is really difficult to find any info about it :( 

Screenshot 2020-04-20 at 18.42.30.png

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look on the internet for each thing you want to know about.  there should be a great deal of info on each one.   you need to educate yourself at least on these basics.

your using the word "play" in connection with such a very dangerous occupation is scary.   please realize that many of us have worked with these materials for many years without problems because we have not PLAYED around.

 

Edited by oldlady
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Hi @oldlady, I've being trying to get info from the internet but for some reason Im not finding it very easy (that's why im asking it here ^^).

Im sorry if the word "Playing" came across as not taking it seriously, it was not my intention. By "playing" I mean enjoying while using these materials and seeing the different results.

 

If anyone could give me a hand with understanding if I can use these materials (Rutile, Ilmenite, Iron oxide and manganese) in mugs, plates, etc. I'd appreciate it :)

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1 hour ago, Mai said:

If anyone could give me a hand with understanding if I can use these materials (Rutile, Ilmenite, Iron oxide and manganese) in mugs, plates, etc. I'd appreciate it

Yes, you can use all of them but please do as @oldlady suggested and read up on them first. The biggest risk to you as a potter comes from silica, it's in the clay and the glazes and can cause silicosis. Good studio hygiene/cleaning can't be understated. Of the 4 materials you are specifically asking about start with reading up on manganese, here is one place to start. What is written about the fumes from the claybodies containing manganese also apply to glazes that contain it. You could look up all your materials and silicosis on that website and find a wealth of information. If you want a more technical article try this one

3 hours ago, Mai said:

Im not getting if all of them (Rutile, Ilmenite, Iron oxide and manganese) are toxic and not microwave friendly...

I'm sorry if I wasn't clear in my post above. It's not that these materials make a pot not microwave friendly, it's that earthenware isn't generally microwave friendly.

Edited by Min
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  • 1 year later...

I have used Standard Ceramics #112 for years for functional ware in the past. However, I decided to make some mortar and pestles as Christmas gifts one year. I decided not to make them with the 112 because they would be grinding, and possibly releasing the manganese into the herbs being ground. I switched to a sister body for this process as it was the same body without the manganese.  Something to think about.

 

 

best,

Pres

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