Mica @ high temps

[Paul Tarlow]

I've noticed that micas disappear at high temps (1500F +).

Where do they go?

Do they burn off (can mica burn -- thought it was quartz)?

Do they dissolve into the glass?

Do they slip through a temporal distortion?

Inquiring minds want to know.

Thanks,
Paul

[Ron Coleman]

They sink into the glass and start to pick up a gloss. Once coverd with a thin layer of glass they go flat and lose the iridescent look.

Ron

[jennk]

Hello! I just registered and am new to fusing and slumping. I have found that when covered with a piece of clear, the green Pearl Ex retains its color but the other colors all go to white. I'm using an old ceramic kiln (from my brother who is a potter) but this is the only problem I've had. The bronze mica powder seems to retain its color whether it's covered or not, but does turn a very nice gold. Haven't had much luck with the other colors.

I just wanted to say also that I've been reading this board for many months now and have enjoyed the pictures and the topics, and have picked up many great hints. Now I'm registered and hope to be able to add my 2 cents' worth every now and then.

[Jerry]

And one more post from the Outpost in Maine. Avery told me that once the mica was set in the glass and cooled it could be fired to higher temps and it would hang around. Doesn't make sense but anyone who can do what she does with an air brush shouldn't be taken too lighty.

Jerry

[Jerry]

And one more post from the Outpost in Maine. Avery told me that once the mica was set in the glass and cooled it could be fired to higher temps and it would hang around. Doesn't make sense but anyone who can do what she does with an air brush shouldn't be taken too lighty.

Jerry

[Paul Tarlow]

And one more post from the Outpost in Maine. Avery told me that once the mica was set in the glass and cooled it could be fired to higher temps and it would hang around. Doesn't make sense but anyone who can do what she does with an air brush shouldn't be taken too lighty.

Jerry

I guess there is a distinction here between "set in" and "set on". I did several test pieces (different glass/mica combos fire to 1350F) and then tried to use them as components in a higher temp firing (1550F) and the mica has completely vanished.

[Cynthia]

guess there is a distinction here between "set in" and "set on"...

I think you may have just hit the nail on the head. Here's my understanding of mica.

If you could look at the particles of the mica powder you would see little plates or discs. When fired high they tip up on their sides and sink into the surface of the glass, so you lose the surface reflective qualities of the mica. At lower temps they adhere to the glass in a parallel or horizontal orientation to the glass, so retains it's reflective properties. Fact or fiction? Don't really know but this is what info I was given.

Also...Pearlex is not formulated to survive firing temps or even be used in this kind of way so many of the colors can burn out. Carefree Lusters by Thompson enamel are specifically formulated for (I forget the terminology, but...) high temp firing and therefore maintain their vibrant colors. Carefree Lusters do hold their color at fusing temps, but can get dull looking because they aren't laying on the surface of the glass, but rather are beginning to sink into the glass. Try firing at 1450 with a hold and see if that keeps if from burning out or looking dull.

Also, if you cap the mica it gives a different effect than laying it on the surface. That is a different topic though, so nevermind.

[PDXBarbara]

Now I'm registered and hope to be able to add my 2 cents' worth every now and then.

Perfect!...because $.02 is the top-tier membership fee around here! Welcome.
Barbara

[Avery Anderson]

Sorry Jerry....I think you misunderstood what I was saying or I was talking too fast and tripped over my words. Micas will sink deeper into the glass with each subsequent firing. My temp for the first fusing is around 1380 with a 10 minute hold. At this point, the micas can still be scraped or scarred, so you have to treat them kindly. However, after the next firing - usually around 1400 - they are very stable. It is difficult to scratch them...I've tried with a key. At this point they would hold up for back splash tiles, architectural eliments, etc. If you go above 1450, you will burn them out for sure and be left with a glazed appearance. I only use Thompson Carefree Lusters.....they are more reliable than PearlEx and some of the others on the market. The interference colors are more difficult to work with and can burn out faster than the heavy metallics....i.e., copper, russet and gold. Once fired to the tack fuse, you can definitely cap them with clear.

Incidentally, Thompson has expanded their mica selection...they now have 14 colors.

Avery

[Jerry]

Avery,
I stand corrected; thank you for straightening things out.

I've fired Mica onto transparent System 96 red at about 1400 successfully and then slumped into a mold around 1350. The results were good enough that all of it sold this summer. But I've not tried fusing uncapped. In previous projects I've encased the mica and gone to ridiculous temps with little fade, but that's probably the luck of the dumb.

Thanks again,
Jerry

[Cynthia]

... In previous projects I've encased the mica and gone to ridiculous temps with little fade, but that's probably the luck of the dumb.

Thanks again,
Jerry

I don't think it's the luck of the dumb. I cap or encase mica pretty much exclusively. The Lusters hold up to even high temp firings without fading or dulling when encased (exception are the interference colors, they can look a bit clumpy and color results seem to be iffy when encased). The problems I encounter when encasing are that the mica can calcine and that causes outgassing that can create bubbling. I have not had this happen with the Lusters, but have had it happen with Pearlex.

I don't have any knowlege as to why the colors hold up better when encased or capped vs being applied to the surface at higher temps, but in my universe that is the case, so am not suprised that you are getting the same results.

[Cheryl Wade]

Hi. I've seen quite a few postings here about micas but, I'm sorry to say, I don't know what they are. Are they same as lustres? And do I mean the same thing by lustres as you? I know lustres as liquid colours including metallics for firing. Is mica metal, how is it packaged - powder or what and how do you apply it? Where can you get it? Are there any sites with pictures showing its effect? So many questions but it sounds like areally good product.
Thanks in advance
Cheryl

[Ron Coleman]

Hi. I've seen quite a few postings here about micas but, I'm sorry to say, I don't know what they are. Are they same as lustres? And do I mean the same thing by lustres as you? I know lustres as liquid colours including metallics for firing. Is mica metal, how is it packaged - powder or what and how do you apply it? Where can you get it? Are there any sites with pictures showing its effect? So many questions but it sounds like areally good product.
Thanks in advance
Cheryl

There is a difference between micas and lusters. Mica is a mineral, sometimes used in lamp shades and wood stove windows because it can be split into thin layers and will not melt at high temperatures.

The mica powders used for glass fusing are finely ground and coated with a microscopic layer of titanium dioxide, The result is an iridescent and reflective coating. Many colors are available. Many products use the mica powders as color agents, makeup (eyeshadow), lipstick (iridescent type) and many paints and plastics.

A sample of one of my pieces done with mica powders

http://www.warmglass.org/gallery/GalColeman2.htm

This piece was done on black Byllseye Glass.

I'm not sure where in Wales you might get mica powders, but for starters you might look where they sell craft supplies. One brand that may be available is Pearl Ex. Pearl Ex powders are sold by Jacquard Products. I know some people have even found them in Australia, so check around.

http://www.jacquardproducts.com/products/pearlex/

One word about Pearl Ex colors, they all do not fire true to color in the kiln. Sure bets are silvers, gold, copper and any of the interference colors (blue, red, green).

One US source for mica powders is Thompson Enamels, they sell Carefree Lusters mica powders (not the same as the liquid lusters)

http://thompsonenamel.com/products/supp ... rials4.htm

All the micas look their best on dark glass. Many posts in the archives about this topic too.

Ron