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Separators - a comprehensive thread

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Hugo Gavarini
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Separators - a comprehensive thread

Postby Hugo Gavarini » Wed Mar 12, 2003 9:06 am

Separators-comprehensive thread

Hello friends,

I thought that a post on separators would be useful to me and to all whom, like me, are a bit confused about the substances which are considered as separators.

Despite my relatively long permanency in the warmglass arena, I remain doubtful with regard to this topic.

I know that Alumina is possibly the best separator, and that it may be mixtured with kaolin to avoid a loose powder coating. In fact, that compound seems to be the one used in commercial separators.

But, why if I use Hidrated Alumina instead, would I expect a calcining temperature where water will be released from the separator?.

Regarding Kaolin, it appears to remain stable up to 1400°F (760°C) when it starts to leave a haze on the glass, thus forcing to renew the separator. Would you agree?.

I read that Whiting, i.e. Calcium Carbonate or Limestone, decomposes at 1517°F (825°C), being that point a limit to the use of Whiting as mold or separator.

I read that Talc (Magnesium Silicate Hidroxide), is used as a separator below 1200°F (650°C) but I don’t know why. Is there a calcining temperature where water is released or what?.

I know that some fusers use even pumice powder as separators, with variable results according to the particular Vulcano Gods.

I would like to know more and deep on separators. Would someone know thermal properties of Alumina, Hidrated Alumina, Kaolin, Whiting, Talc and Pumice?. I am referring to melting or decomposition temperatures, decomposition products (for example, that products from Whiting I guess are Calcium Oxide and Carbon Dioxide), behaviour as separators, and the best way to use each one.

Is there other separator which I have neglected in this post?

Should you consider this post as a valuable theme, please feel free to rebuild it in a more useful dialog tool.

Thank you,
Hugo

Bert Weiss
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Postby Bert Weiss » Wed Mar 12, 2003 9:52 am

Hugo

My knowledge is practical not scientific. The alumina that I use is flour of alumina hydrate. The trick is to get the finest ground product that you can get. Since most suppliers only carry one type, you get what they get. I believe that Bullseye seperator is made with alumina hydrate that is very fine. That is one edge they have, being a manufacturer that can buy a particular grade.

Kaolin does indeed leave a haze on the second firing above 1400ºF

I have found that whiting works well for 1250º but not for fuse firings

Talc is used by people doing low fire slumps for the lighting and furniture trades.

For fuse firings on a kiln shelf, I prefer 80% alumina / 20% kaolin. Remove after every fuse firing. This formula wipes off with a paper towel.

For slump firings on Stainless steel molds I prefer 50/50. More kaolin makes it harder and it will last for many firings.

For dry powder that I coat blanket with and use to create textures, I mix alumina, diatomaceous earth, and plaster. I don't know the proportions. Too much plaster is not good.

I have never worked with Boron Nitride. It comes in formulas that will last at various temperatures. I would like to try some that is made for fuse firings some day.

Bert[/quote]

Tony Smith
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Postby Tony Smith » Wed Mar 12, 2003 11:30 am

Mica can be sifted onto the shelf and used as a separator as well. My understanding is that potters use it. I have used it for full fuse on small pieces and it works very well, but it also leaves a mother-of-pearl sheen on the surface of the glass as some of the mica fuses into the glass surface... not a bad thing if that is what you are looking for. :?

The big problem is that ithe mica moves with the air currents and ends up everywhere if you aren't really careful.

Tony
The tightrope between being strange and being creative is too narrow to walk without occasionally landing on both sides..." Scott Berkun

Bert Weiss
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Postby Bert Weiss » Wed Mar 12, 2003 12:06 pm

Tony Smith wrote:Mica can be sifted onto the shelf and used as a separator as well. My understanding is that potters use it. I have used it for full fuse on small pieces and it works very well, but it also leaves a mother-of-pearl sheen on the surface of the glass as some of the mica fuses into the glass surface... not a bad thing if that is what you are looking for. :?

The big problem is that ithe mica moves with the air currents and ends up everywhere if you aren't really careful.

Tony


Tony

Is there a cheap source of Mica relative to pearlex?

Bert

Tony Smith
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Postby Tony Smith » Wed Mar 12, 2003 12:25 pm

The non-colored mica powder can be purchased in bulk. I'll check with Patty Gray to see where the potters get it. I know the colored micas can be purchased in bulk from Sepp Leaf in New York.

Tony
The tightrope between being strange and being creative is too narrow to walk without occasionally landing on both sides..." Scott Berkun

Hugo Gavarini
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Postby Hugo Gavarini » Wed Mar 12, 2003 2:55 pm

Bert and Tony,

Thank you a lot. When I fired natural mica (Muscovite Mica), the one which is used in some appliances like old irons, I have found that my particular micas went through a calcining transformation around 1450°F (800°C). So, I wonder whether you have to first cure micas when used as a separator prior to a full fusing, to avoid bubbling from calcining.

It is easy to tell whether a mica is calcined or not. Natural mica is almost transparent, clear or light gray, while calcined is notably opaque and nicely colored, looking like gold, platinum or silver.

I remembered that some people use a silica fluor bed as a separator when fusing large sheets. Is this right?.
Hugo

Brian and Jenny Blanthorn
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Re: Separators - a comprehensive thread

Postby Brian and Jenny Blanthorn » Wed Mar 12, 2003 3:54 pm

Hugo Gavarini wrote:Separators-comprehensive thread

Hello friends,

I thought that a post on separators would be useful to me and to all whom, like me, are a bit confused about the substances which are considered as separators.

Despite my relatively long permanency in the warmglass arena, I remain doubtful with regard to this topic.

I know that Alumina is possibly the best separator, and that it may be mixtured with kaolin to avoid a loose powder coating. In fact, that compound seems to be the one used in commercial separators.

But, why if I use Hidrated Alumina instead, would I expect a calcining temperature where water will be released from the separator?.

Regarding Kaolin, it appears to remain stable up to 1400°F (760°C) when it starts to leave a haze on the glass, thus forcing to renew the separator. Would you agree?.

I read that Whiting, i.e. Calcium Carbonate or Limestone, decomposes at 1517°F (825°C), being that point a limit to the use of Whiting as mold or separator.

I read that Talc (Magnesium Silicate Hidroxide), is used as a separator below 1200°F (650°C) but I don’t know why. Is there a calcining temperature where water is released or what?.

I know that some fusers use even pumice powder as separators, with variable results according to the particular Vulcano Gods.

I would like to know more and deep on separators. Would someone know thermal properties of Alumina, Hidrated Alumina, Kaolin, Whiting, Talc and Pumice?. I am referring to melting or decomposition temperatures, decomposition products (for example, that products from Whiting I guess are Calcium Oxide and Carbon Dioxide), behaviour as separators, and the best way to use each one.

Is there other separator which I have neglected in this post?

Should you consider this post as a valuable theme, please feel free to rebuild it in a more useful dialog tool.

Thank you,


Yo Patagonia Boy

My mix is

50 /50 china clay ( kaolin ) / calcined alumina (realy fine)

U can run this in a ball mill 2 get finer

2 this mix I add

Bentonite enough so not settle fast

+ gum arabic ( enough so not B dusty )

Everyting apart from the alumina could give U problems

I always fire slow n vent till 700c

I never clean off just repaint where needed

Here is an old post


Dug this out 4 Ya

Calcium Carbonate Ca CO3 whiting

Calcium Oxide Ca O Lime

plaster of paris Ca O4 . 1/2 H2 O

O is oxigen

I am not shure if they behave the same 4 us

Not got a high temp 4 them as the gas part burns off

Just found melt temt for Ca O Which I guess it ends up as

2580 C - 4676 F

But I belived if U go high it melts

Well maybe I am wrong

While we R on this

Talk is Steatite also magnesium silicate + water 3Mg O . 4SiO2 . H2O

Havent got a melt temp 4 this but its a flux in ceramics I belive

I use it as a mould seporator I dont take it higher

Do UR own tests

Or

To B safe I would recomend a bat wash mix such as

China clay alumina

Shuch as Lovely Lanis Pink ( Bullseye Kiln Wash )

I Miss U Lani U out there ??

Take care when reading posts that U R gona go to the same temps

Wash Boy

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Brad Walker
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Postby Brad Walker » Wed Mar 12, 2003 3:57 pm

I'm currently running experiments with the Fusion Shield kiln shelves, which don't require ANY kilnwash. Early results are promising, but I want to do a few more tests. So far the only major drawback is that the shelves are expensive.

I'll report more when I'm finished with my testing.

Brian and Jenny Blanthorn
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Re: Separators - a comprehensive thread

Postby Brian and Jenny Blanthorn » Wed Mar 12, 2003 4:47 pm

Hugo Gavarini wrote:Separators-comprehensive thread

Hello friends,

I thought that a post on separators would be useful to me and to all whom, like me, are a bit confused about the substances which are considered as separators.

Despite my relatively long permanency in the warmglass arena, I remain doubtful with regard to this topic.

I know that Alumina is possibly the best separator, and that it may be mixtured with kaolin to avoid a loose powder coating. In fact, that compound seems to be the one used in commercial separators.

But, why if I use Hidrated Alumina instead, would I expect a calcining temperature where water will be released from the separator?.

Regarding Kaolin, it appears to remain stable up to 1400°F (760°C) when it starts to leave a haze on the glass, thus forcing to renew the separator. Would you agree?.

I read that Whiting, i.e. Calcium Carbonate or Limestone, decomposes at 1517°F (825°C), being that point a limit to the use of Whiting as mold or separator.

I read that Talc (Magnesium Silicate Hidroxide), is used as a separator below 1200°F (650°C) but I don’t know why. Is there a calcining temperature where water is released or what?.

I know that some fusers use even pumice powder as separators, with variable results according to the particular Vulcano Gods.

I would like to know more and deep on separators. Would someone know thermal properties of Alumina, Hidrated Alumina, Kaolin, Whiting, Talc and Pumice?. I am referring to melting or decomposition temperatures, decomposition products (for example, that products from Whiting I guess are Calcium Oxide and Carbon Dioxide), behaviour as separators, and the best way to use each one.

Is there other separator which I have neglected in this post?

Should you consider this post as a valuable theme, please feel free to rebuild it in a more useful dialog tool.

Thank you,


I am shure zircon has a realy high melt temp

Image
Image

Colin & Helen

Postby Colin & Helen » Wed Mar 12, 2003 6:34 pm

Zircon flour is used in face coats by some bronze casters..so why not glass?? the cost could be a factor?? ... around five times the price of alumna hyd..
Colin

dee
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Postby dee » Wed Mar 12, 2003 8:51 pm

brad - the fusion shelves - are they smooth? also what about bubbles on larger pieces?

D
Dee Janssen
Unicorn's Creations Studio
http://ucjewelry.com
dee@ucjewelry.com

Luiza
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Postby Luiza » Wed Mar 12, 2003 9:04 pm

Do you mean Zircon instead of Kaolin ? Just Zircon and water?
Are the results smooth?
Luiza

Brad Walker
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No Troubles with Bubbles

Postby Brad Walker » Wed Mar 12, 2003 9:04 pm

Dee wrote:brad - the fusion shelves - are they smooth? also what about bubbles on larger pieces?

D


Very smooth. No bubbles at all.

My understanding is that when they first introduced the shelves they did have troubles with bubbles, but they seem to have solved that problem.

I'm using a 12" square shelf, so don't have the ability to test for really large pieces. So far it's performed as well as I could hope for, but I want to do some more firings and use some different types of glass.

If I end up really liking the shelves, I may try to get set up as a distributor. There's certainly potential here.

dee
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Re: No Troubles with Bubbles

Postby dee » Wed Mar 12, 2003 9:54 pm

Brad Walker wrote:
Dee wrote:brad - the fusion shelves - are they smooth? also what about bubbles on larger pieces?

D


Very smooth. No bubbles at all.

My understanding is that when they first introduced the shelves they did have troubles with bubbles, but they seem to have solved that problem.

I'm using a 12" square shelf, so don't have the ability to test for really large pieces. So far it's performed as well as I could hope for, but I want to do some more firings and use some different types of glass.

If I end up really liking the shelves, I may try to get set up as a distributor. There's certainly potential here.


ok, talk to sara creekmore about them - she tried the early version, we've talked about them and that's why i had those 2 questions ;P i had seen their ad in the glass craftsmen magazine tho' i have noticed the last issue didn't have an ad from them

D
Dee Janssen
Unicorn's Creations Studio
http://ucjewelry.com
dee@ucjewelry.com

Sara
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Postby Sara » Wed Mar 12, 2003 10:09 pm

Aii Yii Yii, my first attempt at the board.

Brad, I received two 12"x12" squares last October or November. This was in the first phase of Fusion Shield's product. They arrived with crumpled corners and all scratched up. I have been promised new shelves on at least 3 occasions when I've phoned . . .so far with no results.

Good point, I can fuse without kilnwash!!! Bad points, so far very very POOR SERVICE and even though I've drilled holes all across the test shelves I still get huge bubbles. It does sound like you may have their newer prototypes. I hope they read this and send me the shelves I ordered :) There is great possibility and I personally believe if Customer Service improves they will be worth the monies:)

Warm glass regards,

Sara

Brad Walker
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Postby Brad Walker » Wed Mar 12, 2003 10:30 pm

Couldn't agree more, Sara.

There are a number of things about the company that worry me, starting with their discount structure to retailers (it's horrible), their sales materials (lots of mispellings and such), and the lead times to get the shelves (way too long).

But the version of the product I'm trying does seem to be an improvement over the earlier one. The shelves are smooth, arrived in good shape, and are working well so far. I'm told that the earlier shelves had significant outgassing (the bubbles!), which I'm not seeing this time around.

Bottom line: the jury's still out, but so far I've been pleased with the results. I'll write again after I've had some more experience.

Hugo Gavarini
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Postby Hugo Gavarini » Wed Mar 12, 2003 11:03 pm

Colin wrote:Zircon flour is used in face coats by some bronze casters..so why not glass?? the cost could be a factor?? ... around five times the price of alumna hyd..
Colin



Hello!

I was looking into the matter and have found some information which I would like to share, for what it’s worth.


Hydrated Alumina – chemical formula Al2O3.3H20

When heated this product first loses its water of crystallization at 392°F (200°C) remaining almost pure alumina (Al2O3) which melting point is 3704°F (2040°C). I believe this is called Activated Alumina also, and that it is a very hygroscopic substance, turning back to hydrated alumina if exposed to moisture (when the kiln is kept opened at room temperature). Then, I guess that only hydrated alumina is the commonly commercial available product. We are actually alternating alumina to activated and hydrated forms when heating and cooling it in the kiln. So, beware alumina outgassing up to 392°F!.


Zircon (Zirconium Silicate) – chemical formula ZrSiO4 - Melting point 3992°F (2200°C)


Zirconia (Zirconium Dioxide) – chemical formula ZrO2 - Melting point 4892°F (2700°C)


I don’t know whether Zircon or Zirconia is the material suitable as separator, but I have found that both are used to make glass crucibles.

A note on Zirconium. It carries naturally occurring radioactive elements of the uranium and thorium series. Radiological hazard by inhalation of dust. Although low radiation level, consult MSDS!.
Hugo

Lauri Levanto
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Postby Lauri Levanto » Thu Mar 13, 2003 2:47 am

To add confusion,
when I make a mold for frit casting, the piece is first covered with a splash layer. If that layer is pure plaster, it cracks.
Now I am testing with a 50/50 mixture of kilnwash and
plaster. The first experiment worked fine.

As Hugo mentioned, when kaolin is heated over 760 C
it starts to bond, even to glass. So maybe a mixture
of plaster and aluminium oxide works better.
Have not tried it yet.

-lauri

Brian and Jenny Blanthorn
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Postby Brian and Jenny Blanthorn » Thu Mar 13, 2003 5:48 am

Hugo Gavarini wrote:
Colin wrote:Zircon flour is used in face coats by some bronze casters..so why not glass?? the cost could be a factor?? ... around five times the price of alumna hyd..
Colin



Hello!

I was looking into the matter and have found some information which I would like to share, for what it’s worth.


Hydrated Alumina – chemical formula Al2O3.3H20

When heated this product first loses its water of crystallization at 392°F (200°C) remaining almost pure alumina (Al2O3) which melting point is 3704°F (2040°C). I believe this is called Activated Alumina also, and that it is a very hygroscopic substance, turning back to hydrated alumina if exposed to moisture (when the kiln is kept opened at room temperature). Then, I guess that only hydrated alumina is the commonly commercial available product. We are actually alternating alumina to activated and hydrated forms when heating and cooling it in the kiln. So, beware alumina outgassing up to 392°F!.


Zircon (Zirconium Silicate) – chemical formula ZrSiO4 - Melting point 3992°F (2200°C)


Zirconia (Zirconium Dioxide) – chemical formula ZrO2 - Melting point 4892°F (2700°C)


I don’t know whether Zircon or Zirconia is the material suitable as separator, but I have found that both are used to make glass crucibles.

A note on Zirconium. It carries naturally occurring radioactive elements of the uranium and thorium series. Radiological hazard by inhalation of dust. Although low radiation level, consult MSDS!.


Another thing U could look at is titanium dioxide

Again very high melt temps

I do have some further ideas if U R on the quest 4 the elusive holly grail of

Mirror Wash tm

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charlie
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Postby charlie » Thu Mar 13, 2003 10:17 am

Sara wrote:Good point, I can fuse without kilnwash!!! Bad points, so far very very POOR SERVICE and even though I've drilled holes all across the test shelves I still get huge bubbles. It does sound like you may have their newer prototypes. I hope they read this and send me the shelves I ordered :) There is great possibility and I personally believe if Customer Service improves they will be worth the monies:)

Warm glass regards,

Sara


sara: have you tried sanding or milling them flat?

brad: is this a surface product that is fired onto the board during manufacturing, or is it a property of the material so would be through the board?

if the former, then i would suppose one can't sand or polish the board.


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