Playing in the sandbox

>, tack-fusing>Playing in the sandbox

cabsFun little project that’s worth investigating, one which started with my urgent need for about 600 glass cabochons.

I wanted to get as many cabs as possible out of scrap, so I began cutting up dozens of failed projects and refiring the pieces. Sometimes the results were spectacular, sometimes not…but my absolute favorites came from boxcasting experiments gone wrong.

I’d been experimenting with pate de verre boxmaking methods to get the look of PdV without all the just-under-the-surface bubbles, which make it difficult to carve into the glass without creating pinholes.

So I’d added inner and outer walls of clear sheet glass to the castings to act as a lens for the gorgeous patterns and to let me do some surface carving.

I’d gotten the idea from those sand/sugar painting things that were a big hit in the 80s, where you drip colored sand/sugar into a glass container, manipulate the layers with a stick and create all kinds of patterns. I’d used the same technique to pack my glass walls with frit tints.

The project failed for about seven reasons not worth talking about..but the theory was solid and some of the box walls were gorgeous. I decided to see if I could reproduce the gorgeous parts all by themselves.

The result is 4-5mm thick panel which resembles a potmelt or hot-raking project, or perhaps a pattern bar gone nuts (below). It’s easily cut with a standard glasscutter and breaking pliers, and it both accepts surface carving and incorporation into other projects without much fuss, just like potmelts.

But where potmelts and rakes show solid lines of smooth, fully-melted glass blending into each another, this method produces distinct, textured bands like colored sand paintings. It offers much more control over color and pattern than hot-rake or potmelt, lets a little frit go a very long way and, as long as you don’t go crazy with the heat, retains the cool textural look through multiple firings.

crystalspanelI’d done something a bit like this in 2003 or so, only simpler: I’d piled coarse frit onto a sheet of thin clear glass in patterns, smoothed it out and topped it with another thin clear sheet, then fired to a melty tackfuse. I’d coldworked the edges of the panel and slumped it into a simple plate shape. The result was extremely crystalline, very graphic and shiny…totally different look, as in this panel with shades of blue.

bargellic-6Using smaller frit allows you to get a lot more detail into the panel. If you’re patient (or masochistic) enough, you could probably use this method to create detailed portraits and landscapes, the way they do in the Middle East.

DISCLAIMER: I am NOT claiming to be the first one to do this. Like most glassmaking techniques, its inventor probably died 2000 years ago and I am at best one of many rediscoverers.

So…if you’re a fuser you probably already have everything you need to make one in your studio:


  • Long bamboo skewer, stick, pick, just so it’s longer than the glass you’ve cut
  • Superglue (or a hot melt glue, but the superglue holds better (I think))
  • Invisible (scotch) tape, the cloudy kind–it burns out in the kiln
  • Kilnshelf about two inches bigger on all sides than the panel you’re making
  • bargellic10-4Kiln weights (mullite bricks, stainless steel bowl full of sand, whatever)
  • A jeweler’s scoop if you can find one, or a thin plastic spoon


  • Two sheets of clear or crystal clear thin glass (mine are usually around 8×10 inches). Cut one sheet about a quarter inch shorter in one direction.
  • Enough 1/4-inch strips of 3mm glass to fit all the way around the perimeter of the bigger of your two glass sheets (any color works because you’ll be cutting this off)
  • Frit–powder, fine and medium frit

The type and transparency of the frit strongly influences your result. So if you want (ab0ve)

  1. Strong, sharp graphic lines: Layer high-contrast dark powders (opaque or transparent) with pale opal powders.
  2. Soft, glowing pastel bands: Use mediumbargellicstrip-4– to light-colored transparent powders.
  3. Sparkling, effervescent areas: Build up larger layers of fine transparent frit in pale/clear shades. They tend to trap lots of small bubbles, which reflect light and look glittery .
  4. Blended, very organic and watercolory lines: Use darker, fine transparent frit against a paler color, such as the aventurine green against the spring green . The outlying chunks tend to blend in with the surrounding frit, and the effect is enhanced if you put this layer between medium-to-pale opaque powders.
  5. Scattered small, glowing windows. Put down a layer of darkish opaque powder, followed a layer of much lighter transparent frit in a medium size, followed by another layer of the opaque powder, then tap the mix sharply on your worktable. The powder will sift into the medium frit, outlining its grains.
  6. “Pebbles.” Medium frit in an opaque color gives a pebbly, irregular edge to the color band. If you add a layer of powder in a strongly contrasting color on other side, the powder will sift in to outline the “pebbles.”
  7. Dark outlines. Place any size frit next to a color it reacts with (sulfur glasses such as yellows against a copper glass like turquoise, for example) and you’ll get a fine dark line between them, almost like a cartoon.

bargellic10-3Step 1: Make the “sandbox” envelope
bargellic-emptyboxClean your glass pieces thoroughly, let them dry, then set the longest sheet on your worktable, with what will be the inside of your envelope facing up. Cut a 1/4 inch 3mm strip to fit across one of the shorter sides–this becomes the bottom of your envelope. Butt it up exactly across the bottom and superglue it in place.

Now cut the side pieces, to fit all the way to the other end of the sheet, and superglue those down, too. Finally, cut a fourth piece of 3mm strip that fits between the side pieces. Set it aside for now.

Apply more superglue to the tops of your 3mm pieces and lay the second piece on top, making sure the bottom pieces are aligned (this will make the “top” of the envelope about a quarter inch shorter on one side, below). Press the pieces together firmly to make sure the superglue sets.

You should now have a very thin box of glass, an envelope, with the long sides 3mm apart, and one side of the top a bit shorter than the other.

The superglue is probably enough to hold things together, but if it doesn’t and one of the sides gives way, you’ll have frit all over the place.

For safety’s sake I like to run a strip of tape across the bottom of the envelope and about two inches up the sides to prevent leaks. Then I add another band of tape around the top, about an inch from the edge, just to strengthen things while I’m filling.

I remove the tape when the envelope is filled, sealed and ready for the kiln. But if I forget and leave it on, this kind of tape will burn off without a trace.

Filling the envelope
bargellic-jewelerscoopStart by picking your colors–frit is notorious for looking pastel in the jar but turning out dark, dark, dark after firing, so I usually just grab up the catalog and choose my colors that way.

I tend to stick to mostly monochromatic or analogous palettes with maybe one or two surprises, but really, anything goes. I generally choose 10-12 jars for an 8×10 inch envelope, about 60-70 percent powder and the rest fine and medium frit. You may have to pick the bigger chunks out of medium frit to ensure it will slide easily down the envelope.

It’s helpful to assemble ALL the frit on my worktable before starting. Since I photograph all my glassmaking processes, I also snap a photo of the fritjar stack before I start. That way if I can’t quite remember what went where, I can refer to the photo.

Now, I just open all the jars of frit and start scooping and filling with abandon. You can accidentally spill/drip/drop frit into the wrong jar, contaminating the colors, although (thank the kiln gods) I haven’t done it yet.

It might be smarter to tip out enough frit for the project into individual, labeled paper cups; that way if you make a mistake you haven’t lost the whole jar.

bargellic-driftI fill the envelope using a jeweler’s scoop, essentially a small, flat shovel that scoops up tiny gemstones. It’s exactly the right shape for sticking frit down a 3mm opening. If you don’t have one, you can also use a cheap, thin-edged plastic spoon, or make your own scoop out of sheet metal.

(Just FYI, the jeweler’s scoop is also one of the best tools I’ve seen for applying fine lines of frit or powder to just about anything)

Now, holding the glass envelope in one hand with the short edge facing toward you, scoop up your first frit color. Tilt the envelope about 30 degrees, and rest the scoop on the longer edge of the envelope in back, making sure the shorter edge is just slightly INSIDE the envelope.

(This is why one edge is shorter than the other–it forms a natural ledge for running your scoop back and forth, and also makes it very easy to redirect any stray frit that falls down the front back up and into the envelope.)

Tap the scoop lightly to start the flow, then just slide the scoop, inside the envelope frame, from one end of the envelope to the other. Sliding produces enough vibration in the scoop to slip the frit off and into the envelope. Let it fall a little way down into the sides, to make room for a second run if you need it.

bargellic-3Once you’ve dumped in as much frit as you need, stand the envelope up on its base and tap it gently against the worksurface.

The frit should slide easily to the bottom and settle into place. Now scoop up your second frit color, and repeat the process.

You can fill up the layers in straight, even lines all the way across or lay them down with hills and valleys. Each new layer settles into the crevices left by previous layers.

You can also disrupt the layers and make new patterns using your skewer. Insert it into the envelope and slide it down into the frit layers. Push straight down and you’ll move the top layers of glass into the bottom, creating fine outlines.

bargellic-4Move the skewer from side to side, and you’ll open “canyons” in your layers that will be filled in as you add more frit (above, right). Rock the skewer around a center point, and the powder will move into swirls (left).

Just remember than anytime you push into the powder, or pull the skewer up out of the powder, it will pull a trail of a different color behind. If you are working with reactive colors (i.e., a copper glass with a sulfur glass), your powder trails can start to look like handwriting.

Optionally, you can insert a piece of 3mm glass into the envelope and tamp down the frit. This can be helpful in reducing bubbles, and you can also use it to make shapes. Occasionally tap the assembly against the worktable, which will also help settle the frit and minimize bubbles.

Prepping for the kiln
Keep filling the envelope until the frit is very slightly below the shortest side. Tap it a few times against the table to settle the frit, then slip the cap (that 3mm piece you cut to fit inside the top of the sheets) into the envelope. Push it down a bit (not too hard, or you might break through).

bargellic10When the cap is seated, drip some superglue into either side and let it seal up. Remove the tape, and clean the outside of the panel (both sides) thoroughly. (There’s frequently a bit of powder on the outside; you can’t see it, but it WILL show up in the firing.)

bargellicSet the panel in the kiln, on a clean, smooth kilnshelf, and make sure there’s at least a couple of inches around it. Center your piece of well-kilnwashed kilnshelf over the panel (it should overhang the piece by a couple inches on both sides) and set it on top.

Now weight the center of the kilnshelf–I add about 6-10 pounds of weight, primarily in the center. All that loose frit traps air; the weights help push the air to the edges and also compress the glass to about 4-5mm, making the panel easier to cut and fit onto a piece of thin base glass.

I use a pretty simple firing schedule with a big bubble squeeze to give trapped air plenty of time to move to panel edges.

  • 300dph to 1150F/593C, no hold (heat to the start of the bubble squeeze)
  • 50dph to 1240/671C, hold 60 minutes (bubble squeeze and hold)
  • 200dph to 1485F/807C, hold 45 minutes (process time)
  • AFAP to 900F/482C, hold 2 hours (the extra time is mostly because there’s a LOT of extra insulation on this glass, and I want to give it time to relax evenly)
  • 40dph to 700F/371C, turn off the kiln (let the kiln freefall to room temperature)

It’ll take awhile for the panel to completely cool (those kilnbricks are holding in heat), so I generally wait an hour or two after the controller tells me the inside of the kiln is at room temperature, before removing the panel from the kiln.

Clean the panel well, then cut it up as needed. You need a bit more pressure on the score line than with sheet glass–I keep an older glass cutter for this kind of stuff–and some patience when you’re applying the breaking pliers.

Center the pliers over the score exactly and squeeze very firmly, waiting a few secs (sometimes) for the score to start running. If it doesn’t break right away, switch to the opposite end and start squeezing there. The glass is flat and fairly solid, so I can make clean, square cuts down to about 3/8 inch, maybe 95 percent of the time.

bargellic-crosssection-6The cut is clean, and you can see how little actual frit you use in this method–it’s thinner than the thin clear sheet glass that forms the envelope.

bargelliccabs-2The surface of the panel retains the texture of the kilnshelf on both sides, so you’ll want to fire this a second time to smooth out the texture, gloss it up, and brighten the colors. If you’re planning to incorporate the panel (or pieces of it) into other work using a second firing, that’ll do it. If you want to make cabochons or slump the panel as-is, you’ll need a second full fuse firing, or a lot of coldworking.

The panel surface can scum up slightly, so while I’m not terribly fond of the “sprinkle with clear powder” method suggested by Bullseye and others for shining up a piece, it’s probably the fastest way to get a good gloss on the second firing.

(I don’t like covering scum/devit with clear powder because using too little powder will leave dots of scum behind that look worse than the original scum. Using too much introduces bubbles into the surface that cause their own haze and can also leave pinholes if you coldwork the surface. If you’ve got time (and the equipment), you’re much better off sandblasting and/or coldworking the scummed surfaces to about 400-grit. But I realize I’m in the minority in this opinion.)

If I’m making cabochons, I’ll do a final shaping with the coldworking equipment, up to 220 or 400-grit, and firepolish. That leaves me with a flawless surface and a nice, finished shape.

Postscript: Remember above where I said I wasn’t claiming to have invented anything? Good thing. My friend Bob Heath did some checking, and there is a guy named David Alcala who does indeed make full-blown pictures using this method. In fact, he appears to have started doing this with real sand, sandwiched between two pieces of window glass, then graduated to doing it with frit and tossing the result in the kiln.

So nope, I didn’t invent the idea of sandwiching frit beetween two sheets of clear glass, although there are significant differences between the way I’m doing it and what he’s doing. At best I’ve just streamlined the technique a bit for the kinds of work I like to do. Now that I think of it, it’s so obvious I’m surprised more people haven’t “invented” this. 😉 Thanks, Bob, for checking.



  1. Marilyn R November 30, 2015 at 11:37 am - Reply

    Can’t wait to try it
    Thanks for sharing it
    Yes, I did see some work on blogs of David Alcalas work and it was also glorious!

  2. Dana Boyko August 1, 2014 at 9:32 am - Reply

    Thank you so much for being so clear about this technique- it’s exactly what Ive been dreaming of!

    San Francisco Street Artist
    Since 2004

  3. bob proulx November 29, 2011 at 5:19 pm - Reply

    I always find myself coming back to your blog because of your great tutorials, thanks for being so willing to share.

  4. Kerry April 25, 2011 at 9:49 pm - Reply

    What an absolutely fascinating technique. I love looking at your tutorials, they are so clear and simple to follow. I originally come from the Mallee, a desert in area in Victoria Australia and I love the idea of incorporating the different sands and salts between glass

  5. Dee Janssen April 13, 2011 at 7:36 pm - Reply

    HMMMMMMMMMMMMM this starts some ideas formulating 😉

  6. Tony Smith April 11, 2011 at 12:51 pm - Reply

    Great tutorial and examples. Thanks Cynthia!


  7. chaniarts April 11, 2011 at 8:06 am - Reply

    this technique was used in the magless exchange about 5 years ago, but your writeup is far superior to that which was published previously for that.

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