Rutile Question

[Chantay]

I am about to order some supplies for making glazes.  I saw that you can purchase rutile or rutile light.  Can someone  tell me the difference? And what effect that would have on my glaze.  I thank in advance for help.

 

 

 

[bciskepottery]

http://www.glazefixer.com/postreview.aspx?PostID=202&PostTitle=RE:The%20Difference%20Between%20Light%20Rutile%20and%20Dark%20Rutile

 

http://digitalfire.com/4sight/material/rutile_1204.html

[RuthB]

The rutile question just came up at the studio today. A favorite glaze with rutile is pinholing. I haven't 

ordered any in a while. Has anyone recently ordered rutile that didn't pinhole?

 

Thanks,

 

Ruth

[Norm Stuart]

As bciskepottery points out, Dark Rutile can be made into Light Rutile by firing off the components which create gas.

 

Materials which off-gas near the top of your firing range, leaving pinholes, can be cured by adding a longer hold at the top temperature.

 

In contrast, ware which leaves more pinholes as the hold at the top temperature is extended is a reaction between the clay body and the glaze, or the clay body decomposing.

[Mark C.]

I use ceramic grade which is light rutile from what I read.

I buy it in 50# bags but it comes in all sizes by the #.

Mark

[Chantay]

Thanks for the info everyone, and quick too!!

[Babs]

I have a bucket of rutiile sand from a local mine which no longer operates. WOuld thi sbe no good for glazes requiring Rutile flour, or best used as a body additive?

[Babs]

The rutile I have has been washed and Sieved? It is sparkly black and runs through my fingers easily, looks purer than the above.

I'm goinn to add it to a slip and trial it in  a glaze.

[RuthB]

Norm, rutile got persnickety in the 90's with pinholes that didn't respond to the usual remedies. The long time

source became unavailable. There was a lot of discussion on Clayart at that time... conclusion was to find a rutile that didn't 

pinhole and buy and lifetime supply. Currently, rutile is blended from a number of sources Looking back through my personal archives I found a

suggestion to add or increase lithium. This glaze has petalite, so I'll try that also. Maybe you guys on the West Coast have the good stuff!

 

From Digital Fire;

This material can be inconsistent in the amount of iron and impurities producing variations in color and surface character, thus manufacturers will blend ores from different deposits (Ferro in the US blends various Australian materials in addition to material from Florida). For example, one major American supplier, TAM (now Ferro), relied on a high quality Sierra Leonian rutile deposit until 1995 when political problems in the country cut the supply. Since then no other substitute has provided the same quality. Considering that it is the metallic coloring impurities in rutile that are the subject of its variation and that the function of rutile in glazes is most often partly or mainly as a colorant, it is easy to see that visual consistency variations can be expected when using this material in ceramic glazes. Large users of rutile will often track batch numbers from the manufacturer and test when the number changes. If serious differences are detected another batch may be requested. Failing this the situation can sometimes be dealt with by adjusting the amount of rutile in the recipe or firing differently. In more serious situations adjusting the recipe and employing other materials like iron and titanium might be needed. In any case, it is important to understand the base glaze and the mechanisms by which rutile imparts the desired visual effect. Buying large amounts of a batch that works well is thus a good idea with a material like rutile.

[Norm Stuart]

Ruth  -  I definitely see a difference in rutile glazes every time we purchase a new bag. For a person who tries to control as many of the input variables as I can, I'm surprisingly undisturbed by this.  It's a natural product so I expect variation.  But rutile that continues to react with the glaze and off-gas, leaving pin-holes - that would grab my attention.

 

Was this problem actually occurring with calcined (light) rutile?  If so, my mind races trying to come up with a plausible reason for that to happen, unless it needed to be calcined to the same cone or higher cone as the glaze firing like ^6.

 

That must have been as annoying as buying red iron oxide from Laguna Clay and discovering it contains 15% barium sulfate and fires purple-brown.

 

Using calcinced materials I've only encountered reaction pinholing between fluorine containing frits like 3269 and 5301 and few clay bodies like Half and Half.  That didn't surprise me given how reactive fluorine is. 

 

In refineries, hydrogen fluoride is used as a powerful catalyst (~ flux) in alkylation units which raise the octane of gasoline while lowering its vaporization rate resulting in fewer emissions. The entire process area has HF detectors every few feet which activate high pressure water diffusers capturing any HF leaks into deep beds of granulated calcium carbonate.  http://www.eia.gov/todayinenergy/detail.cfm?id=9971  But by itself, neither 3269 and 5301 frit nor Lithhium fluoride lose weight after firing to cone 6, so breaking these strongly endothermic bonds take more than a cone 6 firing.  I much prefer lithium fluoride to Lithium Carbonate in part because it's more fine, but also provides two types of fluxing activity and better color.

Norm, rutile got persnickety in the 90's with pinholes that didn't respond to the usual remedies. The long time

source became unavailable. There was a lot of discussion on Clayart at that time... conclusion was to find a rutile that didn't 

pinhole and buy and lifetime supply. Currently, rutile is blended from a number of sources Looking back through my personal archives I found a

suggestion to add or increase lithium. This glaze has petalite, so I'll try that also. Maybe you guys on the West Coast have the good stuff!

 

From Digital Fire;

Large users of rutile will often track batch numbers from the manufacturer and test when the number changes. If serious differences are detected another batch may be requested.

 

Buying large amounts of a batch that works well is thus a good idea with a material like rutile.

[RuthB]

Norm, This is the group studio where I teach some classes that's having the problem with rutile. So pardon the slightly second hand information. 

I believe they are using light rutile, but I will check. How high can rutile be calcined? ^10?  And should this be done in oxidation or reduction?

 

I've not used Lithium fluoride, but am getting intrigued by the material. I've had negative experiences with lithium carbonate crystallizing in the bucket

over rather short periods of time. These crystals seem to prefer their own company and refuse to rejoin the rest of the crowd in the glaze no matter what. I dropped

a perfectly nice ^9 clear from the data base because of this. Does lithium fluoride play well with others in the bucket and at ^10? From what I read, escaping fluorine gas would not be 

a good thing for a glaze. Perhaps I should stick with Petalite for my lithium doses. 

 

Thanks,

 

Ruth

[Norm Stuart]

Ruth  -  You can burn most carbonates, and organics off by ^04, which is why it's used for a bisque firing.  Our new bag of Pioneer Talc was a dark grey from carbon.  This caused off-gassing problems from the carbon burning out. 

 

I put that bag of talc into a large ceramic bowl and fired to ^014, with a one hour hold to let enough oxygen penetrate the talc fully.  After the firing, the dark grey talc was now a slightly pink white powder - from the iron in the talc which doesn't burn-off.  It's often cheaper to buy uncalcined materials, but they just create either more problems or more work, so I'd rather buy materials which have already been processed.

 

Combining Lithium and Fluorine is reportedly the second highest exothermic chemical reaction there is.  This means you need that same enormous amount of energy to break them apart - which you just won't achieve in your kiln.  Place 30 grams on some clay previously fired to cone 6 and fire to ^6. After firing the Lithium Fluoride still weighs 30 grams. 

 

The only downside to Lithium Fluoride is it costs $32 a pound in five pound quantity instead of $11.93 for Fine Lithium Fluoride. 

http://www.axner.com/lithium-fluoride.aspx

http://www.axner.com/lithium-carbonate-fine.aspx

 

These are some samples of Pete Pinnell's Weathered Bronze Green each made with 1% of these lithium fluxes:

1.)  Lithium Fluoride;

2.)  Lithium Carbonate; 

3.)  Spodumene.

 

For my taste the choice is clear - and notice the lack of pinholes in the lithium fluoride version which doesn't off-gas.  The Lithium Fluoride glaze doesn't flow  more, but it look more like a glaze than an engobe.

 

 

If you slow-ccol as slow as we do, 50 degrees F per hour between 1,800 and 1,500 - this is one of the glazes I need to add 20% Ferro Frit  3269 to maintain the look.  Without a slow-cool and without the extra 3269 frit these look the same.

 

Spodumene makes a wonderful flux for making flame-proof low-expansion clay bodies, but I don't like the look it creates in glazes.  I have some petalite but haven't tried this as it contains 4.9% Lithium Oxide compared with 8% for Spodumene.

 

Norm, This is the group studio where I teach some classes that's having the problem with rutile. So pardon the slightly second hand information. 

I believe they are using light rutile, but I will check. How high can rutile be calcined? ^10?  And should this be done in oxidation or reduction?

 

I've not used Lithium fluoride, but am getting intrigued by the material. I've had negative experiences with lithium carbonate crystallizing in the bucket

over rather short periods of time. These crystals seem to prefer their own company and refuse to rejoin the rest of the crowd in the glaze no matter what. I dropped

a perfectly nice ^9 clear from the data base because of this. Does lithium fluoride play well with others in the bucket and at ^10? From what I read, escaping fluorine gas would not be 

a good thing for a glaze. Perhaps I should stick with Petalite for my lithium doses. 

 

Thanks,

 

Ruth