Microwave kilns

[nigeljohnson73]

Apologies for mentioning them, but I have one and I love it, I just wish I could produce what I'm after from it If I had the money, I'd have a proper kiln, but I'm working on that. Anyhow I'm struggling with my experimentation and I'm hoping you guys can help.

I'm trying to make some rune pendants that glow in the dark, if I do it right (using 3 x 2mm layers), I may be able to have a background that also has a glow effect as well. Attached are firings 82 through 86 which have finally managed to encase all the glow powder, but I'm suffering with bubbles, which I'm assuming means I need to turn the wattage down on the micorwave and fire longer and slower. If I outline my process can anyone help out streamlining where possible, or provide any constructive feedback

I have 2mm and 3mm opal glass for the bottom layer. If I use 2mm I can paint a "starfield" on that and get a second 2mm layer of clear with the rune on, and a 2mm clear cover. If I use the 3mm base, I effectively have only the one background to draw in and a 3mm clear top.

I use some glow powder that is so fine it will not bear any weight, so I mix it with powder frit (clear) and mix in some glastec glue so it's a toothpaste consistency then use this to make my image. I use a colour pusher to shape until it's stiff/dry enough to hold it's shape then I put it on a radiator to dry, then clean off the mess.

I then need to put a dam around the image so I can get a think edge of glass so that the rune doesn't start poking out the sides. I use 2mm clear and I'm cutting 2mm or 3mm wide strips (depending on what I need to get it to about 6mm total thickness) but I'm struggling to glue this effectively - glastec takes forever to hold. I've heard I can use superglue (cyanoacrylate based), but from what I've seen it's fogs the glass before it goes in the kiln, does this come off?

I then fill the space with fine frit (plus a bit to account for the air space), use hairspray to hold so I can get it in the kiln and then fire.

All of the setup taks about 1.5 hours. can anyone think of any suggestions to speed this up, or suggestions on glass glue that sets quick but burns off well, or anything at all I can do to get better results.

Thanks in advance.

[Valerie Adams]

I'm a bit confused as to exactly what you're trying to do, and I don't use a microwave kiln, but here goes.

Part of your bubble problem is the fine frit; it's trapping tiny air bubbles. I'm not sure why you're using it instead of just capping your image with a solid piece of glass.
And yes, the foggy blur you see from applying superglue will burn out in the kiln. I don't use glue very often but either cheap non-aerosol hairspray or superglue are my choice when I need something.

For the pieces in the photo, I'd likely 'paint' the image onto the opal base layer and then just cap with a single layer of clear.

[nigeljohnson73]

Thanks for the feedback. I did start capping it with clear glass but I had mixed results from even bigger air bubbles or powder pushing out the sides. The powder stands about 1-2mm off the surface, so creates cavities. If you look at the bright red pendant on the far right of the image, the bit in the middle for example, will trap air, even if the cap were to melt pretty evenly.

I could ensure that I never have a gap like that, but even the arrow symbols are producing air bubbles like this.

I think this evening will be retrying with the cap at a lower wattage (slower heating) fine and medium frits at the lower wattage as well.

I think I also read that I can almost slump by putting coarse or medium frit in the corners as this will slow the sagging giving the centre more time to heat and sag?

[Valerie Adams]

Using chads around the outside edges of a cap allows air to escape but these pieces appear too tiny to use that technique.

I don't know what the powder is that you're using to make your images (is that the glow in the dark aspect?). Could you fire your powdered imagery first so it flattens and then cap the pieces with clear? Or perhaps you could Dremel out a channel in your design, then fill it with the powder and cap.

[nigeljohnson73]

Ah, chads, yes, I think that's the use of frit in the corners I read somewhere.

I did think of making the designs so that they don't have a pocket for air, however even with the arrows for example, bubbles still formed. Maybe a combo approach to lift the cap higher on one side so the air comes out of the pocket, or fills along the lines.

I also tried full firing the base and the rune first, but then the glow powder floats out and will blow off. It is a powder by glow-tec that has a tiny particle size and is basically immiscible so does not mix well with anything for long. I did tack fuse the base and rune as well, I think that was worse overall as the glass frit then turned solid and I seemed to have more air trapped - probably psychological more than factual.

I also thought about making glass clay with the glow powder and powder frit mix. This way I think I can make a very thin sausage and make the rune, then press the cap on to flatten the rune out a lot more. Hmm... That may be a project for the long weekend.

[Lynn Perry]

Nigel, I have some of the glow powder, too, and played with it a little. One thing I did discover is that the equipment used to produce the frit left a lot of metal contamination. I was able to remove the debris with a strong magnet.

[nigeljohnson73]

Soooooooo confused!!!!!

Right so I started with damming the pendant and incorporating the small bubbles into the design - fizzy runes were born. I also tried pieces of 3mm glass as chads but nearly every single time regardless of fine/mediun frit of chaded caps, a large air bubble formed somewhere that spoilt the pendant. (representative samples are the top row in the attached image)

Rather disheartened I gave up to work on a separate idea - fizzy heart in a tear drop. Using exactly the same glass blanks as previously only cut in half, the same powder for the icon, the same damming method, the same over height of medium frit... and not one single inappropriate air bubble. This was the case regardless of heart size or firing time. (middles row is every one I did) Also, some of these are 2mm backs with 2mm dams some are 3mm backs with 2mm dams.

reheartened ( ) I thought it was all about the shape of the rune, so I used the same heart shape and size, but guess what - a single big bloody bubble nearly every time of 5 attempts (again, a mix of 2mm and 3mm backs, 2mm dams and medium frit) I even made sure that in every time there was a piece of frit in the heart gap bit.... WHAT GIVES!!!!

Can anyone explain what's going on? My sanity hangs in the balance.

[JestersBaubles]

reheartened ( ) I thought it was all about the shape of the rune, so I used the same heart shape and size, but guess what - a single big bloody bubble nearly every time of 5 attempts (again, a mix of 2mm and 3mm backs, 2mm dams and medium frit) I even made sure that in every time there was a piece of frit in the heart gap bit.... WHAT GIVES!!!!

Can anyone explain what's going on? My sanity hangs in the balance.

Think about it...

Your hearts are all one solid design that sits on the glass. The runes, however, are multiple lines. The multiple lines are creating areas that trap air. For instance, look at your ohm symbol (OK, I'm sure it's not an ohm, but I play with dataloggers all day... I don't cast runes ). The bubble is trapped inside the upper arc of the ohm.

I am not familiar with glow powder, but this web site indicates it is prone to causing bubbles:

http://www.sundanceglass.com/glow-glass-powder-info.htm

Dana W.

[nigeljohnson73]

hi Dana, thanks for posting.

The capturing of air I had thought about, I'd hoped that I could let the cap melt onto the design, but in the case of the leo starsign/ohm symbol it has a double loop so I would only be able to use frit here I guess. I did think I could use a chad to drape the cap over the design right to left, but it didn't work.

If you mix the glow powder 2:1 with powder frit, I've noticed there is very little air popping out with the teardrop shapes. The problem is though that even when I go back to the rectangular cabochon the air pockets reappear, even though there is frit in there.

The only thing I can think of is that the surface tension of the glass handles differently with the pointier shape. A' level physics escapes me

[nigeljohnson73]

Sorry, I meant to clarify. If I use the heart shape on the teardrop shape, no bubbles, if I use exaclty the same heart shapes and sizes on the rectangular shape, I get large air pockets in the crease of the heart in about 2/3rds of the time.

[haleybach]

With the triangle shape the hearts look like they are closer to the edges. If so, this is making it easier (faster) for the air to escape.
That is my best guess.

A microwave kiln was my gateway kiln. They don't seem to like anything that involves frits or powders.

[nigeljohnson73]

I think I'm on to some things, thanks to all the feedback.

1) new bag of medium frit, less bubbles - I think because the bottom of the previous bag collects the powder and crap.
2) lower power on the microwave, about 350watts (I think) means 25 minutes before anything glows, but I'm thinking faux "bubble squeeze"
3) thicker part of the item closer to the wall seems to mean more even heat up - it's a fine line though.
4) ensuring there is enough space round the heart so a bit of frit can sit between it and the dam otherwise an air bubble will form, same with corners in the heart.
5) Medium frit likes to bounce a lot, and it ricochets a lot - Newton would be proud.
6) adding the glow powder and glass mix to the glue mean less air in the mix.
7) fine detail or lines with the icon seems to channel bubbles, anything blob like seems ok, hearts, stars etc.
don't be too clever, it's a microwave kiln

I think I will invest in a kiln, but I can only really afford one that doesn't have the multiple cycle controller, but it's a step up from the microwave in that I can fire multiple items at a time and it's a lot more controllable.

Thanks for all your feedback guys