WarmGlass.com

Hello everyone! I'm a long-time lurker! I've found the advice on this forum invaluable, and thank you all for sharing your knowledge. My Mother was a glass artist all her life (along with paint: acrylic, oil, and watercolors) and while she gave me lessons, I never really did much on my own. When she passed, I got all of her tools and equipment and glass, and the glass bug bit! I now have a studio in my home (a whole room!) and I'm truly enjoying myself.

I've been doing mainly stained glass, with some smaller fused/slumped items in my Evenheat Studio 8. I just bought my first "big boy" kiln, a Jen-Ken 15/6, and started fusing and slumping larger items with much success...

Until yesterday! I tried my first pot melt. The results... Not so pretty. I bought a ceramic 8 inch minimelt bowl and casting ring. I used an online calculator and used 5 ounces System 96 Cathedral yellow waterglass and 5 ounces System 96 Cathedral blue waterglass - both scrap I had in my studio. I cleaned both well.
I used Hotline Hi-Fire shelf primer on both the casting ring (inside and bottom lip) and the kiln shelf, 5 coats. Fully cured in oven at 500f for an hour.
I cut both colors into quarter-sized pieces, and placed the blue to one side of the bowl, and yellow on the other.

Here is my firing schedule:
Ramp 600/Target 1700/Soak 90
Ramp 9999/Target 1540/Soak 30
Ramp 9999/Target 960/Soak 60
Ramp 50/Target 800/Soak 0
Ramp 100/Target 700/Soak 0
Ramp 200/Target 100/Soak 0

When the kiln was at 86 degrees, and the room temp was around 80 I opened the kiln. The bowl had a glaze of blue and yellow where the glass was. I read that would happen. I lifted the bowl...

First... Ugly. The circle was flat, but the glass in the ring was just over 3/4 blue, with the remaining yellow and blobby. I went to lift the ring off. It resisted just a very little, then came off... And the glass circle looked to be shattered! The whole thing had broken into many pieces. Not only that, but 1/8 inch of the inside of the ring, almost half the diameter, had chipped off and bonded to the glass! I tried picking the pieces off of the kiln shelf - slight resistance, and a little kiln wash was on the bottom of the pieces.

So please tell me, what did I do wrong??

a few things

1700 is just too hot. It will always cause problems with kiln wash sticking. Since we use Bullseye shelf wash I just do not know how Primo works under these conditions. I always sand down the shelf and kiln wash fresh before every melt. No need to dry the shelf.....by the time the glass drips it is dry.

If the ring you used is stainless steel.. (?)..I would suggest always using 1/8" fiber paper on the inside of it. That gives a buffer for the expansion difference between the glass and the steel. I never kiln wash the steel.

Not knowing the thickness of the melt I always anneal longer at the anneal temp.....usually 3 hours then cool slowly as you did.

The ugly factor.......You will just have to test with different color combos till you get something that rings your chimes.......I like to add white in the mix on almost every melt. It makes the colors swirl and stand out.

so why did it shatter?.....probably the fact that it stuck to your ring.

A personal opinion on using white in a melt. Stay away from Bullseye 013. It seems to change COE at the higher temps and then stress cracks start to show up. This does not apply to Eryc as he is using System 96.

Laurie Spray wrote:a few things 1700 is just too hot. It will always cause problems with kiln wash sticking.

Thanks! What temperature would you suggest?

Laurie Spray wrote: If the ring you used is stainless steel..

Nope, I used a ceramic ring. Would a stainless ring work better? How come?

Laurie Spray wrote: Not knowing the thickness of the melt I always anneal longer at the anneal temp.....usually 3 hours then cool slowly as you did.

Noted, thank you!

Laurie Spray wrote:The ugly factor.......You will just have to test with different color combos till you get something that rings your chimes.......I like to add white in the mix on almost every melt. It makes the colors swirl and stand out.

Also noted, again thanks! I have been reading - it seems like dark colors should be used VERY sparingly. I'll have to remember that.

Mark Wright wrote:A personal opinion on using white in a melt. Stay away from Bullseye 013. It seems to change COE at the higher temps and then stress cracks start to show up. This does not apply to Eryc as he is using System 96.

Thanks, I'll add that to my notes in case I ever do use Bullseye.

The recommendation that you line the ring with fibre paper remains valid whether stainless or ceramic.
It is probable that your high top temperature was too great for the kiln wash. The crazing that you have is typical of glass sticking to the shelf. Bullseye kiln wash seems to perform better than some at higher temperatures.
I generally use 900ºC for my top temperature (only 25C below yours)

Stephen Richard wrote:The recommendation that you line the ring with fibre paper remains valid whether stainless or ceramic.
It is probable that your high top temperature was too great for the kiln wash. The crazing that you have is typical of glass sticking to the shelf. Bullseye kiln wash seems to perform better than some at higher temperatures.
I generally use 900ºC for my top temperature (only 25C below yours)

That would make sense - the glass is moving as the temp drops, but the bottom of the glass isn't able to move, just the top so - cracks! Do you think I should try again using the same kiln wash (so I don't have to buy more) BUT using the lower temp? The shelf itself wasn't damaged. And I'll line the ring with Papyrus I have.

I wonder if Spectrum's Papyrus shelf paper on the shelf would work??

Also , it would be good if you are aware of potential reaction of colors which react when fired next to each other. Spectrum as well as BE.

I do mesh melts [not pot melts] at 1700, but stay there only few minutes, as by then most of the glass had already dripped.

Following an advice of one of the Guru's here, I put fiber paper [3 m'm, not thin fire] to collect the melt, I feel its safer.
I would recomend to you to read Steve Immerman's tutorial at clearwaterglass.com - you will find good explanations there..

good luck,

Havi

Havi wrote: Steve Immerman's tutorial at clearwaterglass.com - you will find good explanations there..

Lots of good info there, thank you!

No.....you need 1/8th inch to line the ring. You could try your P. shelf paper on the shelf, put a clear blank onto it and drip onto that......but it is to flimsy for the walls and too thin to give you the pad......