REUSABLE MOLDS FOR GLASS CASTING - Rio...

Many of our newer designs look best when cast very thin. These designs included:

• All our leaves, e.g. Oak Leaves and Acorns, Tropical Leaves, Assorted Small Leaves, and Leaves (3)

• All our flowers, e.g. Dog-wood, Rose, Blossoms, Small Mixed Blossoms 1 and 2, and Lotus

• Honey Bees, Small Dragon-flies, Small Butterflies

• Lily Pad and Frog

A complete list of designs to which this applies is in “Fill Weights at a Glance.” This document is located in Colour de Verre’s Project Ideas section.

Just how do you go about getting a thin, light weight casting?

First some background: There is a force called “surface tension.” Sur-face tension causes any liquid to “bead up.” (An everyday example is the way rain drops bead up on a car’s hood.) If glass is hot enough, it will bead up, pull away from the mold’s edges, and thicken.

Here are the secrets to thin cast-ings with fine details:

✓Use the Thin Fire fill weighs that can be found in “Fill Weights at a Glance.” This lower fill weight is usually about two-thirds to half the fill weight shown on the packaging. One can add more or less frit to cus-tomize the casting size.

✓Use fine frit. It requires less heat work to conform the smaller particles to the mold’s surface.

✓Use lower temperatures. These accompanying schedules are designed to barely fuse the frit particles together, but before the glass becomes fluid. At the low end of the temperature range, the piece will have a matte, “sugar fire” finish. At the high end; a glass-like finish.

Every kiln is different and firing schedules can be affected by glass thickness, number of pieces in the firing, number of kiln shelves, whether the kiln has top and/or side elements, and even glass color. However, here are two firing schedules – one for COE 90 and one for COE 96 – that can serve as starting points for thin, fully fused, finely detailed castings.

Many of these molds have built-in slumpers to add “life” to the final piece. A slumping schedule is also included.

REUSABLE MOLDS FOR GLASS CASTING

Tips for Thin CastingsAs people become more experi-enced with our molds, they start wanting thinner and more deli-cate castings. Let us pass along these hints and advice to achieve that goal.

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AvailabilityColour de Verre molds are available at fine glass retailers and many online merchants including our online store, www.colourdeverre.com.

COE 90 Firing Schedule

Seg 1! 300˚F/hour to 1375-1400˚F, Hold 10 minutes

Seg 2! AFAP (As Fast As Pos-sible) to 960˚F no vent-ing. Hold 30 minutes

Seg 3! Off, cool kiln, no vent-ing

COE 96 Firing ScheduleSeg 1! 300˚F/hour to 1350-

1375˚F, Hold 10 minutesSeg 2! AFAP (As Fast As Possi-

ble) to 960˚F no vent-ing. Hold 30 minutes


Slumping Schedule

Seg 1! 300˚F/hour to 1225-1250˚F, Hold 5 minutes

Seg 2! AFAP (As Fast As Pos-sible) to 960˚F no vent-ing. Hold 30 minutes


May 2009

Given the finished piece, one might think of this as too complex a project for a beginner. Actually, this project can be completed by people new to glass casting. The trick is to approach the project as four “mini projects”:

• Create a collection of ginkgo castings. Make more than you expect to use so that you can ex-periment with various layouts.

• Fuse two pieces of sheet glass together to create the panel.

• Tack the cast leaves to the panel.

• Slump the panel using a shallow form.

Create the Ginkgo LeavesBefore each firing, clean your molds with a stiff nylon brush to remove any old kiln wash. (This can be skipped if the molds are brand new.)

Give each mold cavity four thin, even coats of Hotline Primo Primer. Each gingko mold has six mold cavities built in, but since there are three on each side, only three ginkgo leaves can be cast per firing. It is not necessary to prime mold cavities that won’t be filled.

Hotline Primo™ primer is the only conventional primer we rec-ommend because it doesn’t ob-scure the mold’s fine detail and is easy to remove after firing. Use a soft brush to apply the primer and a hair dryer to completely dry each coat before applying the next. The mold should be completely dry before filling.

If you prefer, you can use boron nitride aerosol primer. (We used this for our project) We recom-mend ZYP exclusively. You can read more about this in Advanced Priming with Boron Nitride Aerosol which can be found in our web-site’s Project Ideas section.

The ginkgo leaves are cast from a combination of fine Moss Green and fine Yellow frit. To create vis-ual interest, three different frit combinations are used.

Combination #1:30% fine Moss Green70% fine Yellow




Ginkgo PlateThis low, shallow plate is a great accent for a dining room table.

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Tools✓Ginkgo Leaves mold✓Small and Large artist’s brush✓Small containers for mixing frit✓Digital scale

✓Assorted kitchen measuring spoons

Supplies✓Hotline Primo Primer or ZYP✓Fine Moss Green and Yellow frit✓Moss Green Frit and Stringer on

Clear; Clear and White Streaky sheet glass

✓Powder Black frit.

Combine the two frit colors in lid-ded containers and shake to com-bine. (Empty frit jars work per-fectly.) Whenever mixing frits, it is highly advisable to wear a dust mask.

As mentioned above, each mold has six casting cavities, three on each side. The fill weights for Side A, the side with the “Ginkgo Leaves” text are 9, 9, and 9 grams. the fill weights for Side B, the side with the copyright text, are 15, 7, and 14.

To accentuate the subtle veining, sprinkle ¼ to ½ gram (a pinch) of black frit into each cavity. Hold the mold in place with one hand and use the other to tap the mold. This will cause the black powder to set-ting into the mold’s shallow groves. Using the fill weights mentioned above, evenly fill the ginkgo leaves. Lightly tap the mold to level the frit and transfer the mold to the kiln. Fire the molds according the Component Casting Schedule. (See “Tips for Thin Casting” in the project section of Colour de Verre’s website.)

If the castings “ball up” decrease either the hold time or target tem-perature. Given the differences between individual kilns, it may take one or two test firings to get perfect results in your particular kiln.

Creating the PanelCut a 10x10” (25x25cm) square from each piece of sheet glass. Protect the kiln shelf with primer or a piece of ThinFire™ shelf pa-

per. Stack the Moss Green frit and stringer glass on top of the white and clear streaky glass. Place the stack in the kiln and fire according to the Sheet Glass Fusing Schedule below.

Attaching the ElementsRemove the fused panel from the kiln and place on the workbench. Create a pleasing arrangement of ginkgo leaves on the fused panel. Use small dabs of white glue to temporarily hold the components in place. When dry, move the panel to a kiln shelf that has been protected with primer or a piece of ThinFire shelf paper. Fire the

piece according to the Tack Fuse Schedule.

Slumping the PanelPlace the panel into a primed slump mold. Slowly fire the piece according to the Slumping Sched-ule. It is important not to rush the firing as there is quite a bit of thickness variation.

VariationsThere are many combinations of sheet glass and frit color for which this technique produces beautiful results. One we found particularly pleasing was a 14” round disk cre-ated with Black Streamer Bits on


Component Casting Schedule*Segment Ramp Temperature Hold

1 300ºF/165ºC 1340-1360ºF/725-735ºC 30 minutes

2 AFAP 960ºF/515ºC 30 minutes. Off* Schedule for COE 96. For COE 90, increase casting temperature by 25ºF/15ºC. AFAP means

“As Fast As Possible”, no venting.

Sheet Glass Fusing Schedule*Segment Ramp Temperature Hold

1 250ºF/135ºC 1200ºF/650ºC 30 minutes


3 AFAP 960ºF/515ºC 60 minutes

4 100ºF/60ºC 700ºF/370ºC Off. No venting* Schedule for COE 96. For COE 90, increase casting temperature by 25ºF/15ºC. AFAP means


Clear sheet backed by an off-white or Almond sheet.

Ginkgo leaves were created using the following frit combinations:

Combination #1:30% fine Medium Amber70% fine Pale Amber



As before, a little black powder was sprinkled into the mold to ac-centuate the detail.

A “random” pattern was collaged and tack fused into place.

The tack fused disk was shaped using a shallow bowl slump form.


Tack Fuse Schedule*Segment Ramp Temperature Hold




4 50ºF/30ºC 800ºF/425ºC None



Slumping Schedule*Segment Ramp Temperature Hold



3 150ºF/85ºC 1250ºF/675ºC 10-20 minutes


4 50ºF/30ºC 800ºF/425ºC None



U s e H o t l i n e P r i m o Primer. We tested many kiln washes and primers

from a number manufactures. Only Hotline Primo Primer of-fered us the three properties that we required: thin, even coats that don’t obscure the design; consis-tent release; and fired primer can easily be removed with a stiff brush.

Mix the powder with water ac-cording to the label instructions. Apply four to five thin coats to the mold’s inside surface. Let each coat dry before applying the next. A hair dryer can be used to accel-erate the drying between coats. Keep the primer well stirred. The primer’s fine particles – the active components – settle out of the mixture rapidly. If the primer set-tles, the particles will start to cake on the container’s bottom. Use a

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stiff brush to stir the compacted particles off the bottom of the container and back into solution. It is not necessary to pre-fire the mold as long as the primer is dry.

After firing the mold, use any nylon kitchen brush or a toothbrush to remove all

traces of the primer from the mold. We strongly recommend wearing a dusk mask.

Always follow the firing schedule recommended on our website and packag-

ing. Colour de Verre molds are made from a specialized ceramic material. Like glass, this ceramic will crack or shatter if it is heated or cooled too fast.

Finished pieces will have much smoother edges if you use a small brush to

move the frit away from the top edge of the mold. This “trough” only has to be 1/8-inch wide and deep.

Use only crushed art glass or frits in Colour de Verre molds. The molds are not

designed for Pyrex glass, float glass, or crushed bottles. We don’t recommend firing Colour de Verre molds above 1500°F (815°C). At higher temperatures, the primer will start to fuse and becomes more difficult to remove.

If the finished piece doesn’t fall out of the mold, don’t panic. Turn

mold face-down and tap it against a hard surface cushioned with sev-eral layers of newsprint. If the

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piece still doesn’t fall out, the mold probably wasn’t properly primed.

Occasionally, a few glass spurs might be on edges of the finished pieces. These

are easily removed with a wet diamond block or grinder. Follow-ing hint #4 will minimize these.

Butterflies, dragonflies, flowers, and leaves can be given more life with a sec-

ond, slump firing. Some of our designs have a specially designed slumping surface on the reverse side.

A “sugar fire” yields won-derful results with Colour de Verre snowflakes. Fill

the mold to half of the recom-mended fill weight with fine frit. Fire to a “partial fuse” – about 1300°F (705°C). This technique can be used with any of our molds.

Don’t be afraid to experi-ment. Add CMC solution to your glass powders to

make a pate de verre paste. Mixed crush dichroic with your frits. Tack fuse finished pieces to slumped plates and platters. Mix shredded copper, silver, or gold foil into your frits. Embed smaller forms inside of larger, clear forms. The possi-bilities are endless.

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Tricks of the TradeWe want our customers to have a great experience and wonder-ful outcomes with our molds. Let us pass along these hints and advice.

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REUSABLE MOLDS FOR GLASS CASTING - Rio...

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