Working with Metal Inclusions

I recently ordered some glass online and received a free gift of some gold metal butterfly inclusions. I have not worked with inclusions before. I decided to experiment. This is what I did.

  • Cleaned the thin metal butterfly with alcohol.
  • Cleaned a piece of white opal glass to use as the base.
  • Placed the butterfly in the center of the base glass.
  • Capped with a piece of cleaned clear glass.

Then I full fused using this schedule:

  • 500 degrees/hr to 300 - hold for 5 minutes
  • 800 degrees/hr to 1465 - hold for 10 minutes
  • AFAP to 950 - hold for 30 minutes
  • 175 degrees/hr to 800 - hold for 10 minutes
  • Cool to room temperature

Result - The butterfly is dull and discolored in some spots - shiny in a few spots. There is a large bubble at the head of the butterfly, a smaller bubble at the tail, and a small bubble at the side of each wing.

So what did I do wrong? How can I avoid the bubbles and get the butterfly to stay shiny (or at least uniform in color)? Did I fire too hot? Too fast?

All feedback/suggestions are welcome!

Thanks, Barb

Your firing schedule is too

Your firing schedule is too fast unless it is a very small piece.  You should also include a "bubble squeeze" with inclusions.  This is usually done at about 1100 with a hold that depends on the size of the piece.

Keeping the metal shiny can be done by several methods......either coating with boric acid paste, coating with unique clear paint, etc.


Bubble Squeeze - when?

At what point in the firing schedule do you do a bubble squeeze? My piece was very small - a 1 inch circle - which I fired with several other jewelry pieces using my "normal" jewelry firing schedule. So should I fire pieces with inclusions separately and more slowly or was that schedule too fast for even the 1 inch piece?

Inclusions require more care

Inclusions require more care in firing - they expand and contract at radically different rates.

The soak at 300F is strange to me, It does not seem to do anything.  Instead use your initial ramp rate up to 650C or so with a soak of say 20 mins, since it is small.  Your rate of 800F (ca 400C) is liable to promote bubble formation, as it gets the surface of the glass hot very quickly and the bottom glass is still relatively cold.  Slow down.  Keeping a bright surface on brass is difficult.  In addition to the suggestions already made, you could coat the metal in clear powder - compatible with the glass you are using of course.

Stephen Richard

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Hate to be contrarian here,

Hate to be contrarian here, but I doubt that what you  have is gold. I don't think anyone would give out gold pieces for free unless they were decals.

If they are decals, the first thing you need to do is remove the top tissue. I have seen students leave the tissue on without realizing it.

Firing schedule for decal firing is the same as fewelry schedule except vent the kiln to 1000°F



Barry Kaiser

Web Site

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Not Gold or Decals

No the butterflies are not gold - just gold-colored. I believe they are brass - definitely metal and not decals.

And thanks for the tip about the tissue on the decals. I didn't realize it until someone else mentioned it a couple of days ago. I didn't know the top layer was supposed to come off, but I can't say that I've fired with it still on because all of my decals have turned out just fine. So do some decals come without the tissue on them or have I just been lucky?


Soak at 300F

My kiln (a Skutt Hot Start Pro) has several pre-programmed schedules. All of them start with the soak at 300F so I assumed that step is unique to the smooth operation of this particular kiln. So I just include that segment in any of the programs I write - I figure it can't hurt anything...

Thanks for the input!


Manufacturers' schedules


Go to the website for the glass you are using.  They all have suggested schedules.  They will be better than one that is trying to cope with all the possibilities.  These schedules are better places to start, as they know their glass better than anyone else.

Stephen Richard

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