Time-sensitive question: Rutile wash + colored slip

[Meredith Walker]

I'm still in the learning stage re using rutile.

First question: Can two bowls that have a cobalt oxide-colored slip plus an added rutile wash be stacked rim to rim in a bisque fire? 

The effect I wanted from the rutile was drips / runs of the cobalt slip. The bowls are Little Loafers clay (white); when they were soft leather-hard I put them on the wheel and brushed on the slip, starting from the rim and spiraling to the bottom. Then with another brush I applied the rutile wash over it. I'm going to bisque fire them today about 1 p.m., hence the time-sensitive part. 

Second question: What's a good formula for adding rutile to a batch of colored slip? And should I add powdered rutile, or rutile wash?

Thanks very much for help.

[Norm Stuart]

Both rutile and cobalt oxide/carbonate are very refractory and will not melt in a bisque - but other ingredients you add to the slip might.

Granular rutile fired to cone 6 doesn't change much in most glazes, remaining as the same brown spots they looked like when you add them to the glaze.

Granular rutile or ilmenite added to clay results in the speckled brown spots similar to those seen in fired Laguna Speckled Buff clay.  Unfired that clay is an odd pink color.

The only way to know what things will look like in advance is to fire test tiles.  Test tiles are a very underused tool.  When you refer to a rutile "wash", what does this mean to you other than rutile and water?

[Meredith Walker]

Hi, Norm - thanks for your reply. To me a rutile wash is rutile + water. But actually I bought a small bottle of Mayco rutile wash to experiement with, and I don't know what else is in there. I take it from your question that if I'm making my own using powdered rutile, there would be other materials included.

The slip I used is just the clay body + water.

I could have safely gone ahead with firing the bowls rim to rim, I know now, and sort of thought that at the time. But I'm (over)cautious when I do something in ceramics I haven't done before -- need to get over that, I think! Anyway, I took out the top bowl, and started my bisque a few hours ago. Oh, and of course yes, to test tiles. ;)

Thanks again.

[Norm Stuart]

I've been using a 20 year old bag of Dark Rutile for glazes which always created nice strands, as in the Honey glaze below.

Once we began using a newly purchased bag of calcined Light Rutile, we've created glazes which are uniformly opacified rather than strands.  I've been able to recreate so of the strand behaviour by reducing the amount of rutile by about 2/3 - but the artistic result is negligible when compared to our old bag of rutile.  Most annoying.

We'll purchase a bag of Dark Rutile, but I don't have high expectations for recreating the original look.  It appears that all Rutile in North America is sold by the TAM subsidiary of the Ferro Corp, consisting of a blend of Australian and American Rutile.

Rutile is being produced by Sierra Leone, likely the source of our very old bag, but I can't find a place which sells it.  Does anyone  have any ideas?

Honey Glaze, made with very old Rutile and a new bag of Light Rutile

[Nadine Mercader]

The rutile supply I have gives the strands you like. I believe it came from US Pigment.

[Norm Stuart]

Thanks so much Nadine, I'll give Sayed Abbas a call.  He does sell best quality material.