Little Boxes

I seem to have moved one more step forward on the ongoing path toward better sintering. I was thinking about the analogy of “twins in the womb” and how to extend it to apply it to pieces in the firing box. If twins in the womb steal nutrition from each other, could that be what happens to pieces in the box? If each of them had its own separate space, would they not manage better somehow?

I usually avoid placing a small piece next to a big one, since in my experience, the small ones do not sinter properly. This seems a bit counter-intuitive, since I would expect smaller pieces to sinter better. However, statistically this is the case, and it may be because the heat flows towards the bigger and heavier pieces. So theoretically, if we surround each piece with an insulator such as fiber paper, the heat may not be able to flow from one area in the box to another.

I made a small box from fiber paper for every piece I wanted to fire in a single batch. I filled the kiln with more pieces than I usually do – each in its own little box – and included small, big, and hollow forms of copper and bronze. I used my regular firing schedule for Quick-fire Copper and Bronze, and all sintered beautifully.

Here is how to make the box:

Use fiber paper, ⅛” thick (cheap, and available from glass fusing supply stores). Cut a square.

Cut squares at all 4 corners, each about 2″ square.

Fold the wall upwards and staple.


Make boxes of varying sizes for different-sized pieces.

Fill half of each box with carbon.

Place the pieces in the boxes and fill the boxes to the top with carbon.

Fit as many boxes as you can in the kiln, avoiding the center. (Or could it be that with this method, there is no need to avoid the center of the kiln? I tried it once, and it worked!)

I have fired three times so far in the same boxes, and both the paper and the staples are still intact.

Here is another option: use the fiber board box that I described in my last blog posting.

Cut strips of the same fiber paper, about 2″ wide, and use them as separators.

16 Responses to “Little Boxes”

  • marilyn mckay Says:

    Great Idea! Thanks

  • Tamara Culp Says:

    Now this is very interesting. The heat sink theory does seem to apply. I will try it next firing! I applaud your fertile and ever active mind, Hadar ;o}

  • Julia Rai Says:

    Hi Hadar,
    I’m really excited by this! I’ve had some trouble with sintering when I put lots of pieces in the carbon so I’m going to try this method. To be able to really pack the kiln with bronze and copper pieces will be much more cost effective.
    Thanks for sharing!

  • Michele Milana Says:

    Sure makes FINDING the little rascals a lot easier! I have to try this, thanks Hadar.

  • Virginia Vivier Says:

    I am experimenting with hollow spheres. I need to burn out the dried cork clay in a prefire. Can I fire them without using the little boxes when burning out the cork clay first? Or, would it be better to use the little boxes? I am having problems getting all the cork clay to burn out, leaving a rattling sound inside the sphere.

  • Hadar Jacobson Says:


    I would try to burn the cork clay inside the box. Give it up to 1 hour at 1100F before continuing to the firing temperature.

  • Kristi Bowman Says:

    Can you use Fiberglass fabric? It seems very much like some of what you had at our class. I picked up a swatch at Tap plastics to test. She said it could withstand high heat but when I said 1500+ she said she didn’t know about that.

  • Hadar Jacobson Says:


    I tried it. Doesn’t hold so well. Finally I decided to use it as a kiln liner, and one day (probably after firing steel) it disappeared, and there were glass residues on the kiln floor.

  • Annette Holbert Says:

    what is the idea behind avoiding the center of the kiln.

  • Hadar Jacobson Says:


    The temperature at the center of the kiln is lower than closer to the fingering elements. So, unless you kiln is very small, pieces in the center may not sinter well.

  • Sherry Bleiweiss Says:

    I am new to this but am very inspired by all that is possible! Thanks..There just aren’t enough hours.
    Sherry B

  • Melody Pierson Says:

    Hi Hadar,

    Can we also use different size fibre blanket boxes?

    They must be raised a bit for space between the box and the bottom of the oven…?

    Melody P

  • Hadar Jacobson Says:


    Yes, and yes.

  • Phoebe Says:

    hmmmmm, speaking of counterintuitive, you’ve said you’ve moved away from stainless steel containers because they are poor conductors of heat. Yet the fiber blankets/sheets are used as insulation to conduct as little heat as possible. Is it possible that steel is a problem because it conducts, or retains, heat too well? I can see how the steel containers were first chosen, as traditionally kiln work involved working with glass, and ceramic or steel forms are the most commonly used, mainly because of their ability to withstand the high temps. Coming from a glass background, that’s the first thing I would think of to use in a kiln, so maybe it was just habit rather than research that picked the steel containers in the first place.

  • stephanie Says:

    CAn I fire more than one piece per little box?

  • Hadar Jacobson Says:

    Stephanie, there is hardly any room for more then one piece, unless they are very small.