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Member Since 28 Jun 2010
Offline Last Active Yesterday, 09:45 PM

Posts I've Made

In Topic: Converting Electric To Gas

Yesterday, 07:29 PM


In Topic: Shortage Because Of The Weather Up North

Yesterday, 07:16 PM

This sounds like a wonderful opportunity for an industrious person with a truck and time on his/her hands . . . selling boxes of porcelain, stoneware, and e-ware at your neighborhood corner: Need a fix? I've got just what you're lookin' for.

In Topic: Decorating Slip

02 March 2015 - 07:45 PM

Adding oxides or stains to dry clay body and adding water makes a good slip. I also sieve my slips to make sure the oxides/stains are thoroughly mixed. For stains, I usually use a ratio of 10% stain to powdered clay body. For oxides, it will depend on the oxide -- especially the cobalts which are very strong and you only need a small amount.

You'll find a lot of good information at Vince Pitelka's website: http://iweb.tntech.e...ndouts-info.htm

In Topic: Adding Vent To Older Kiln...

02 March 2015 - 07:39 PM

I leave my vent running from start of the firing (bisque and glaze) and turn it off when the kiln has cooled and I'm ready to unload.

In Topic: Cobalt Wash

02 March 2015 - 07:31 PM

Cobalt wash
I’ve bought some Cobalt Oxide and want to use it to give a graduating colour on a mug.  Darker at the top, lighter at the bottom.  ^04 bisque and ^6 glaze fire.
I've spent ages researching, and have found loads of info, the but the following comment seems the most helpful.
“They must be applied over (not under) a glaze for successful results. Application of oxide washes under a glaze often results in areas of 'crawling,' in which the glaze pulls back to reveal the clay underneath. Chrome oxide and cobalt oxide are especially likely to cause galze crawling when applied under a glaze.” From here: http://seco.glendale...depainting.html. with no recipe or instructions given for making the “wash”.
I also found reference to adding a “flux” to the cobalt.

When you apply an oxide wash on bisque, the oxide usually dries like a fine powder on the surface of the bisque (and smudges quite nicely). When you apply glaze over that oxide dust, the oxide acts the same as any type of dust or dirt that prevents the glaze from adhering . . . so the glaze tends to crawl because of the dirty surface. Applying just an oxide/water wash to greenware does not help as much as the bisque temperature is not high enough to melt/fuse the oxide to the clay body -- which is why oxides tend to remain powdery after bisque. Adding the flux to the oxide wash lowers the melting point so the wash adheres during a bisque firing. Lessons learned from experiences with RIO.

Cobalt is a strong colorant . . . so getting variations is going to be hard without adding something to the cobalt to soften the color. Maybe try some combinations of cobalt and rutile or cobalt and tin oxide/zircopax, etc.

Unless you are wedded to using cobalt, it might be easier to get gradients by using a series of blue mason stains or equivalent stains to get the progression you are looking for.