Make Custom Ceramic Texture Molds For Fused Glass Art, by bgartman

This tutorial was written by bgartman and found here.   Sometimes some posts disappear as time goes by and this is such a great tutorial that I didn't want to lose it!  
 

This tutorial will explain how I make custom ceramic texture molds to create fused glass art.
Items used in this tutorial:

1) Firing the clay, and glass:
Kiln: I use a Paragon Janus 23 multi-purpose kiln (capable of firing glass or ceramics with the flip of a switch!)
kiln shelves
kiln shelf wash: Hotline Primo Primer Kiln Shelf Wash
plastic lidded container to mix and store shelf wash in
paintbrush to paint shelf wash onto shelves & molds (I use inexpensive Chinese brushes that are often used for glazing ceramics as shown in the photo)

2) Clay: MCS Porcelain P'Clay Cone 6 available at Baileypottery.com
https://www.baileypottery.com/clay/tuckers-pclay.h...

3) Glass:
Bullseye coe90 glass available at Bullseyeglass.com and other retailers
glass marbles such as Panacea Marble Accents often available at craft stores such as JoAnn Fabrics & Michael's
recycled Glass such as wine bottles, window glass, etc.

4) Items for creating texture in clay:
leaves
clay carving tools
textured objects to press into the clay including commercial stamps, found objects, buttons, etc.

5) Items for rolling out the clay:
rolling pin
rubber rib for smoothing clay
two 1/4" or 3/8" thick strips of wood
plastic backed fabric drop cloth, or regular drop cloth
cornstarch- I keep mine in a sugar shaker to make it easy to powder the surface of my clay
paper towels

Step 1: 

1. Creating the Clay Texture Mold

I've chosen a cone 6 porcelain paper clay as my ceramic medium for making texture molds because it has a very smooth surface that captures texture in great detail. The clay dries quickly, and creates lightweight molds, which is great for loading fused glass projects into the kiln and also great for storing your molds once they've been bisque fired. Most companies ship clay in 25lb blocks with a 50lb minimum. Please note that paper clays are prone to mold if not used quickly, which doesn't affect the quality of your ceramic piece, but may cause problems for people who are sensitive to mold. Most websites selling ceramic paper clay explain the pro's and con's of their products, along with firing instructions.
Decide what texture and design you're going to create. I've created wonderful texture molds from items found in my yard: lotus leaves, lily pad leaves, tree leaves. I've also hand-carved textures to create specific designs. Once you have your design in mind you're ready to start.

1. Work Surface:
Cover your work table with a drop cloth. I love using a plastic-backed fabric drop cloth because it protects my wooden work surface from the damp clay.

2. Clay:
Open your bag of clay. Use your wire tool to cut the amount of clay you need to roll out for your project. For instance, to create the large texture mold of of the lotus leaf takes a greater amount of clay than to create a small soap dish mold.

3. Rolling & smoothing the clay:
For most of my texture molds I roll the clay out to around 1/4" thick. If you're creating a deeply textured fused glass piece like a hand-carved pattern, you'll want to roll the clay to around 3/8" thick.
Follow basic clay techniques for rolling clay by using your rolling pin to work the clay slowly into a flat consistent thickness: Roll, flip the clay over, roll, flip the clay in a new direction, roll again until you have the desired thickness and size for your mold. I try to make mine molds 1/2" to 1" larger than the finished textured design in case the glass flows beyond my design in firing.
If you come across any bubbles in your clay surface while rolling the clay, poke them with a pencil tip or clay knife tip to make sure that they're gone before you proceed with smoothing and texturing the clay.
Take your rubber rib and smooth the surface of your clay, stroking across the entire surface of the clay with the rib horizontally, then vertically. Flip the clay over and do the same procedure again, smoothing the surface of the clay with the rubber rib by stroking across both horizontally and vertically until smooth. Now you should have a beautifully smooth piece of clay, ready to decorate with your textural design.

4. Texture the clay:
Sprinkle the surface of the clay lightly with cornstarch to keep your tools and leaves from sticking. Keep in mind that you do NOT want to press or cut your design completely THROUGH the the clay. Be careful to leave at least 1/8" thickness of clay in the thinnest areas or your mold may be more prone to breaking. As you create your texture, the hollows/deeper impressions in your mold will be the raised areas on your glass surface, and the raised areas on your mold will be the hollows/impressions on your glass surface.
A) If you're pressing leaves into the surface, arrange the leaves on the surface into the pattern you desire, then roll over the surface with even pressure with a rolling pin. I then like to take my fingers and press the leaves more deeply into the surface of the clay to make a deeper impression.
B) Add carved details, rubber stamps, press in objects as desired
C) It's a good idea to create a rim to contain the melted glass by slightly raising the edges of your clay from your table.

IMPORTANT MOLD DESIGN RULES:
-Make sure that your design does not include "under-cuts", or places where the surface of the clay mold juts out over carved hollowed-out areas. The glass will melt into these areas and get stuck.
-If you want to create a thicker piece of fused glass, you'll need to create a rim to contain the glass in your mold. If you do create a rim, be sure that it gently slopes OUTWARD so that the glass will release easily out of the mold.
-The smoother your mold, the smoother the glass. I like to make sure that all of the edges of my textured pattern feel smooth, and that there are no areas in my design that could create a jagged or sharp glass surface.
 
5. Dry your mold:
Follow the clay manufacturer's instructions. Paper clay is very forgiving, though all clay is prone to warping if dried to quickly. I like to leave my mold on my work table for a few hours covered loosely with a layer of paper towels. Once it is firmly leather hard I carefully move it to a kiln shelf in my garage and wait until the ceramic mold is completely bone dry. During the colder winter months I dry the molds indoors rather than in the garage.

 

Colour de Verre Cabbage Leaf Mold Tutorial

Colour de Verre has a lot of really nice molds for glass fusing.  One of our favorite molds is their cabbage leaf mold.  Click on the link below, found on the Colour de Verre website, to learn how to fill this mold with frit and fuse.  Use the leaves to create beautiful bowls and plates by layering multiple leaves.

Click here to view the Cabbage Leaf Mold tutorial.

Video showing how to make a plaster mold

This video isn't made for glass fusing, but it really shows how to make molds and if you use the correct glass mold making materials, you can easily create glass fusing molds this way! 

Click here to watch this mold making video.

Video for Creating a plaster mold for Pate De Verre

Hi readers, are you wondering how to make easy plaster molds for Pate De Verre?  Watch this YouTube video to see a very simple, yet effective way to quickly make your own plaster molds!  
This video was made by Bobby Wadey.   

Click here to watch the video!

Day of the Dead Sugar Skulls in Pâte de Verre VIDEO

 Day of the Dead Sugar Skulls in Pâte de Verre 

This is an excellent video to watch (and take notes on) for anyone who wants to make kiln glass frit casts with molds.  It lists all of the necessary materials needed to use and shows how to, in detail!   Made by Bullseye Glass Company.

Watch the video here!

Devitrification on glass when doing pot melts into small molds

I have been experimenting with pot melts into some small molds that I have, but I always seem to have devit on the top side!  I have been looking online for an answer to what I'm doing wrong, but as of yet I haven't been able to figure out why this is happening.  

I found this post here:

"Paradoxically, aperture pours (pot melts) and high fire slabs, which are often fired above 1600F and held there for long periods of time,  usually resist devitrification. This is because the glass is continuously moving, flowing, and presenting new surfaces during the period of time the temperature is very high."

I'm thinking that the artist above is making larger pot melts or has a better kiln schedule!

So I discovered so far that it doesn't matter what type of glass I'm using, I always end up with devitrification.  I changed my kiln schedule so that I would quickly heat up the kiln to a slightly higher temperature than my original kiln schedule, that way I wouldn't have to hold it there as long, yet I still ended up with devit.  So right now the only solution I know of is to use a lap sander on my pieces, or sandblast the devitrification off.  

I am planning on manually venting my kiln down to the annealing temperature next go around to see if it makes a difference. 

If anyone has any suggestions, please comment below!  Thanks

Repairing a cracked or broken glass mold

#1. Magic Mender - 4 oz. container is for sale on the Slumpy's website. Use Magic Mender to repair chipped or broken slump molds. Use magic Mender to fuse two molds together. Fix hairline cracks in molds. Just apply magic mender to area to be fixed and fire at 1700 degrees F. 

Helpful Hints for Magic Mender:

While the mender is still moist, the joint will be fairly delicate, so be careful when cleaning the mold. The Menders must be fired to become permanent. Keep unused portion in jar tightly closed. The mender has a long shelf life and will not spoil! After firing, the repaired area is stronger than the rest of the mold. If you clean well before firing you’ll never know the break was there.

How to fix hairline cracks:

Use a knife tool or dermal to open the crack. (You must get the mender deep into the crack for it to work, otherwise the crack will reappear.) Dip a brush in the mender and in some water so that you have a flowing consistency. Allow the mender to flow into the cracks, then let dry. If you need a second application, do so, then clean the mold and fire.

#2. You can also use a resin based cement that is used in kiln building called "Sairset". It should be available in all ceramic suppliers.  Make the edges to be joined wet. Spread some Sairset on the joint. Wipe all of it off the working surface with a wet cloth or sponge. Back up the repair with more Sairset on the back. Wash all tools used immediately or the Sairset will never come off. When dry, fire to about 800C. , then wash the mold and you are ready to go.

Tools needed to melt wine bottle and other glass

Occasionally someone will ask me how I melt my wine bottles and other art glass projects.  As crazy as this sounds, I have seen, from looking around online, that some people are actually trying to melt bottles in things like barbecue grills and fireplaces.  And of course that won't really work!  It may be possible to somewhat melt the glass but it will probably permanently stick to where ever it was melted and ruin things.  And that process is never precise.  So I found this information on WarmGlass.com with great information on how to really get started properly!  I hope this helps. 

Aside from the glass, the most important item you need is a kiln. Most kilns used are electric and are capable of reaching temperatures of around 1800 degrees Fahrenheit. Kilns are available in sizes ranging from less than a cubic foot to big enough to fill a room. Kilns made specifically for ceramics can be used, but it's better to have one that's specifically engineered for firing glass.

Your kiln must have the capability to accurately monitor and display the inside temperature. This is usually done with a pyrometer, a precise thermometer that is often coupled with a controller, a device that helps manage the firing of the kiln. A controller can greatly simplify the task of precisely directing and monitoring the temperature changes inside the kiln. You can get by without a controller if you're willing to keep a closer eye on the kiln, but a pyrometer that can accurately measure the temperature inside the kiln is essential.

In addition to the kiln, you need a shelf to set the glass on and (if you want to slump) a mold to help shape the glass. Shelves are generally made of clay or a lightweight refractory material, while molds can be made of clay, stainless steel, or various kinds of cements and plaster mixtures. The key is that both the shelf and the mold can withstand heating up to a temperature of 1700 degrees Fahrenheit or so and then cooling back to room temperature.

You'll also need some sort of glass separator to keep the glass from sticking to the kiln shelf and the mold. The separator can be a special kind of paper that glass won't stick to at high temperatures (called fiber paper) or it can be an emulsion that you apply to the shelf, then allow to dry (commonly called a shelf primer or kiln wash). Without this separator, glass will stick to the shelf or mold when it gets hot and your piece of artwork will be ruined.  

  

That's it. If you have some glass, a kiln, a shelf or mold, and something to keep the glass from sticking, you have the basic ingredients to begin fusing and slumping. Add some tools to help cut and the glass and a few essential pieces of safety equipment, and you're ready to begin.

Bullseye box casting tutorial

To view the original article and pictures follow this link Bullseye Glass Tips Sheet 5.

This Tip Sheet will introduce you to ways to create a reverse relief cast 
glass object with the optical clarity of a furnace casting, using plaster silica 
design elements in an open face mold assembled from vermiculite board and 
other refractory materials. In this process, there will be less waste than with 
traditional kilncasting processes and the majority of the mold will be reusable. 
The molds themselves will be of uniform thickness, allowing for even heating and 
cooling. Furthermore, the molds will not fail at casting temperature, which is 
among the most common concerns in kilncasting and one of the reasons that there 
is such a boggling array of mold recipes in use. The results are typically much 
cleaner and more predictable than kilncasting in most of the traditional methods, 
and the process is extremely easy to repeat for the purposes of making editions or 
production work.


Origins of the Method
This method of kilncasting developed as an outgrowth of an artist exchange project
in our Research & Education department with Mexican artist Rafael Cauduro. Cauduro 
had originally come to the factory to work in methods known as Painting With Light, 
but quickly became intrigued with kilncasting processes and began to make large-scale 
cast glass sculptures using traditional “monolithic” or one-piece refractory molds. 
The fabrication, handling, and technical challenges posed by making and firing 
these molds ultimately led the R&E team, assisted by Ray Ahlgren,* to begin researching 
other ways of building the molds. After the conclusion of the project, this research 
continued. TipSheet 5 will lead you through the processes that were subsequently 
developed.


Where you are going:  The finished piece
The end result will be a solid block of glass with relief imagery in the back of the 
piece that when viewed through the flat front creates a nearly holographic image. 
The top surface of the piece will be glossy and smooth. If carefully planned and 
executed, the top perimeter will have a soft, bullnosed edge. Occasionally, some 
cold work may be necessary or may be a tremendous advantage in the finished work. 
The finished block will measure about 19.5 x 19.5 x 4cm. These dimensions may be 
enlarged by adapting the general guidelines and adjusting the firing schedule.



Materials Needed
Glass: Because clarity is essential to creating a reverse-relief casting, we recommend 
using any of Bullseye’s 1800 series casting tints in billet form. Because they have 
smoother surfaces and less surface area by weight than other forms of glass, billets 
will trap less air than frit, powders, or sheet glass, and therefore create fewer bubbles
in the final piece. Billets are preferable not only for the clarity they produce 
in the finished casting, but also because they are easy to handle, cut, and load into the 
mold. The 1800 series glasses are formulated to gradually transition in color saturation 
as they go from thick to thin, making them ideal for this and other casting processes.
Other materials:
• Clay and tools for modeling design elements
• Metric scale
• Metric ruler
• Bullseye Hydrogel N (8242), or similar moldmaking material
• Mixing containers
• Bucket of water for initial clean-up
• Bucket of water for rinse
• Bullseye Vermiculite Board (8240)
• Stainless steel (deck) screws
• Bullseye Investment (Plaster-Silica) (8244), or similar refractory investment material 
• Fiber paper (7036)
• Vaseline/petroleum jelly
• Murphy Oil Soap
• 946 ml Ziploc food storage box, or equivalent
• Garbage can with liner
• Self-lubricating glass cutter
• Hammer




Notes on Metric measurements
For the sake of simplicity, all units of measure in this TipSheet are Metric. 
The decimal format of the metric system and its direct and simple translation from 
length to volume to weight in water makes it a superior system for laboratory work.
in the metric system: 1 cubic centimeter (cm3) of water = 1 milliliter (ml) of water = 
1 gram (g) of water.  If the interior of an empty box measures 20 x 20 x 2.5 cm, 
then this interior has a volume of 1000 cm3. 1000 cm3 of water is equal to 
1000 ml of water, which is equal to 1000 g of water. Bullseye glass is 2.5 times denser 
than water, so it would take 2,500 grams of Bullseye glass to fill this same volume.

Making a mold for multiple copies of a model
preparing a model using clay or a found object:
Prepare a model no larger than 5 x 5 x 3 cm using either water- or oil-based clay. 
This model will be used to make the design elements that will create the reverse 
relief imagery in the final casting. Water-based clay is usually softer than oil-based
clay, can be modeled very quickly, and can be reused and recycled. However, it 
will dry out over time and will shrink as it does so. Oilbased clay is usually firmer,
does not dry out, holds fine detail very well, is reusable, and releases very easily 
from most mold materials such as alginate, rubber, and silicone. Found objects 
may need to be coated with a release, such as Vaseline or Murphy Oil Soap.



For this particular process, the model itself should have minimal undercuts. 
Undercuts on found objects can be filled in with clay. The very bottom portion of 
these design elements will end up being submerged in investment material to 
hold them in place in the final casting process, so plan accordingly.




Preparing to pour a mold:
Place the model into a box with a minimum of 15 mm
of space all around it; a 10.5 x 10.5 x 9 cm flexible plastic food storage box (Ziploc)
with a slight draft to the sides works well. The box serves as a coddle system, or 
a set of dams, into which you will pour the alginate to make the mold. Use something 
like petroleum jelly to secure the model to the bottom of the box to keep it from 
moving or floating once you have poured in the mold material.


Types of flexible mold material 
for casting multiple copies:
Hydrogel N mold compound is a type of alginate that is fairly easy to mix and sets in 
5-10 minutes. It is somewhat weak with a short working life and will dry out 
and shrink over a couple of days, but if kept in a sealed container and treated carefully, 
it will usually last a few weeks.

RTV Rubber (Room Temperature Vulcanizing) is activated at room temperature but can have long set times and often takes 24 hours to cure into a very durable, very strong material.
For the sake of expediency, we have used Hydrogel N to illustrate this TipSheet.

Mixing hydrogel N mold compound:
Measure box/coddle system—including 1.5 cm above the model in the calculation. 
For our specific box and model, this is 10.5 x 10.5 x 4.5 cm, which equals 496 
cubic cm, which means that it will take 496 grams of water to fill the box to the 
appropriate level. The manufacturer of Hydrogel N mold compound recommends 

mixing it 3 parts water to 1 part Hydrogel N by weight and adding the mold 
compound to the water, but we have had good success mixing it 4 parts water to 1 
part Hydrogel N by weight and adding the water to the Hydrogel. For our project, 
then, we will need 496 grams of water and 124 grams of Hydrogel. We have 
had the best success mixing this with a spatula in a bowl using a folding, not a beating 
motion, to avoid creating bubbles in the mix. Work in a well-ventilated area and 
wear a NIOSH-approved respirator whenever working with powdered materials 
or dusts.


Pouring the hydrogel:
Be certain that you are working on a flat and level surface. Pour to one side of the object
in a flowing motion to keep air from getting trapped on the surface of the model. 
Vibrate the worktable so that the air bubbles don’t get stuck to the model.


Cleanup:
Using water immediately makes a mess. Allow remaining Hydrogel to dry in the
container and then immerse in bucket of water for initial clean up. Once cured, it is 
possible to peel the Hydrogel out as a skin. Never pour into a sink.

Removing the mold from the coddle box:
Turn the coddle box upside down on the work table and squeeze and push the flexible 
walls to let air into the sides until the mold drops out. Turn the mold over 
again and squeeze it and push carefully to force the clay model out. You now have a 
flexible mold for pouring multiple copies of your model in another material.



Making design elements out of refractory mold material
Many different refractory mold (or “investment”) materials and recipes exist. In our 
factory Research & Education department, we use a simple mixture of 50% #1 Casting 
Plaster and 50% silica flour (295 mesh) mixed by weight.


Measuring mold material:
Measure the original model and overestimate its size; it is better to discard some 
inexpensive investment than to run out and have to quickly mix more. Our model is 
roughly 5 x 5 x 5 cm = 125 cubic cm. Referring to the Investment Ratio chart on page 8, 
we can add together the amounts of material needed for voids of 100, 20, and 5 
cubic centimeters to get the proper quantities of water and investment required for 
our 125 cubic centimeter void. This means that we will need 79.99 grams of water 
and 139.98 grams of investment. Weigh these materials in clean, dry buckets. Remember 
to work in a well-ventilated area and wear a NIOSH-approved respirator whenever 
working with powdered materials.


Mixing investment material:
Steadily sift all of the required investment into the water. An island of dry material 
will begin to form once you have sifted most of the material into the water. Allow 
the investment to fully hydrate/become saturated. If left alone, the investment can 
sit for quite some time. Once the mixture is saturated, dip your hand in and 
break up any chunks. Feel the consistency. You want a creamy texture. Mix the 
investment by hand for 3–5 minutes or with an electric mixer/drill for 1–2 minutes. 
This will cause the plaster to begin to work so that it will subsequently set.


Pouring the mixed investment into the mold:
Be certain that you are working on a flat and level surface. If you have a lot of fine detail,
begin by brushing some investment mix into the details in the mold, which will 
break the surface tension so the mix can go into the details. Aim for one place in 
the mold and pour in a flowing motion to avoid creating bubbles. Once 
you have finished pouring, vibrate the work surface to make certain that no air is 
trapped within the details of the mold.

Cleanup:
Clean investment mixing buckets right away. Old plaster in mixing buckets, on hands
and/or on tools will cause subsequent batches of investment to set before 
you have a chance to pour them. It is good to use black
or colored buckets so that you can easily spot old plaster in them. Never pour
investment into a normal sink as this will clog your pipes. Pour excess investment into 

a garbage can that has a liner in it. From there, have two buckets of water to use in your 
cleaning operation: one bucket for cleaning and scrubbing the mixing buckets and one 
bucket for rinsing them. When these buckets become too filled with waste investment to 
continue using them, allow them to settle, then pour off the excess water and dispose 
of the waste investment in garbage bags.

After investment has set up:
It usually takes 5-20 minutes for the investment to set. Lightly touch the surface of the 
investment to test its hardness. Once it has set, the plaster/silica design element can be 
removed in the same fashion that the clay model was. Immediately after setting, the 
design element will still be a little soft, which means that it can be easily modified 
with simple clay tools at this point. After the design element hardens, it can still be 
modified, but you may need to use power tools for the sake of speed.  Store the 
alginate/Hydrogel mold in a closed container for later use, being careful to keep 
it from drying out.





Building the box mold with vermiculite board

Vermiculite board:
Vermiculite has a bad reputation because it is often mined in the same places as 
asbestos, which can contaminate the vermiculite. Bullseye Vermiculite Board comes 
from a mine that is certified asbestos free. It is stronger, more durable, and less 
expensive than most fiberboard and can be cut and tooled like wood or particle board. 
Work in a well-ventilated area and wear a NIOSH-approved respirator whenever 
generating dusts.  If you want your finished piece to be level and square, it is 
important to cut the vermiculite boards accurately. Also, pre-drill and countersink 
screw holes so the board does not bloat or blow out when you screw it together. Use 
stainless steel screws to put the mold together as they will hold up to repeated firings 
without flaking. Do not use galvanized steel screws because upon firing, the galvanization 
will release toxic fumes and the screws will flake and cause contamination in your kiln.
Cut two long side boards at 25.5 x 9 x 2.5 cm, two short side boards at 20 x 9 x 2.5 cm, 
and one base board at 25.5 x 25.5 x 2.5 cm. Lay the boards out as an open box 
and pre-drill holes in the flat surface of the long side boards to connect them to the ends 
of the short side boards using a bit that has a diameter slightly smaller than the diameter 
of the stainless steel screws. Be sure to drill your holes on center to avoid blowing out the 
side of the board. Then screw the sidewalls together. Next, set the base board on top of the 
assembled side boards and pre-drill holes to join it to the sides, and then screw it together. 
Then take the entire box apart and fire the vermiculite board at a rate of 500°F (278°C) 
per hour to a temperature of 1580°F (860°C) or about 55°F (30°C) higher than the temperature 
at which you will cast the glass. Hold at that temperature for half an 
hour, and then crash cool the kiln.Once the boards are cool, take them out and 
reassemble the sides using the stainless steel screws. Cut a piece of 3 mm fiber paper at 
25.5 x 25.5 cm and set it on the base board, then set the assembled sides on top of the fiber 
paper, and screw the box together. Line the side walls with 3 mm fiber paper, making sure 
that it fits tightly, without bowing or leaving gaps in the corners.

Affixing design elements within the box
The design elements must be held firmly in place for the glass casting process. To hold 
them, a shallow layer (or “bed”) of investment is poured into the bottom of 
the box around the design elements.  Hydrate the plaster/silica design elements by soaking 
them in water until the bubbles quit rising (5-10 minutes). This helps to keep the
plaster/silica bed from sucking in around the design elements due to differences in 
humidity. Arrange design elements on the interior base of the box. Check once again to make 
certain that your work surface is flat and level.

example
Measure the inside of the box to determine the appropriate amount of investment
material needed. Our box is 19.5 x 19.5 cm, and we need enough investment to 
fill it about 0.5 cm deep. Thus, the investment needs to fill a void that is 190 cubic 
centimeters. Referring to our investment (plaster/silica) mixing table you will see 
that there is a batch listed for 200 cubic cm, which will be more than enough.
Mix the investment according to the previous directions and pour it quickly and
evenly. Avoid pouring the mix directly onto the design elements or the side walls. 
Vibrate the work surface to make the investment level out.Set aside the box mold 
for 24 hours to make sure that all of the plaster/silica components of the mold have 
cured to an adequate hardness. As with the design elements, you may choose to
modify the affixing layer of investment.


Selecting glass
You may select any form of Bullseye glass to fill the mold (billet, cullet, sheet, frit, etc.), 
but the form that you select will have a direct impact on the clarity of the 
casting. The smaller the form of the glass, the more air bubbles in the finished piece, 
the less optical clarity. Powders and fine frits will create so many air bubbles 
that even our Crystal Clear 1401 will appear milky white and opalescent when used 
at this 4 cm thickness.Because this is a reverse-relief casting and the intention is to see 
the imagery created by the design elements through the surface of the finished piece, using 
billets will give you the desired clarity.

Calculating glass to fill the mold:
Measure the inside of the box mold. Then figure out the cubic volume. Use a specific 
gravity of 2.5 for Bullseye glass to calculate how much glass will be needed to 
fill the mold to the desired thickness. (Bullseye glass is approximately 2.5 times 
heavier than water.) 


Our box mold:
19.5 x 19.5 x 4 cm (desired thickness of casting) = 1521 cm3
1521 x 2.5 = 3802.5 (grams of glass needed)
This does not account for the displacement of glass caused by the design elements.
If you would like to account for the displacement caused by the design elements or if you 
have an irregularly shaped mold, you can use rice for a more precise measurement. 
Fill your mold with rice to the desired thickness of the casting. Then remove the rice 
and decant it into a container. Level the rice, and then mark the level. Remove the rice 
from the container, and weigh the container. Then fill the container with water 
up to the former level of the rice, and weigh it again. Subtract the weight of the container 
to get the weight of the water. It will take 2.5 grams of Bullseye for every 
gram of water.Use a reliable scale to weigh out the amount of glass you will need.

Cutting the billet:
Use a self-lubricating glass cutter to score glass and about the same amount of pressure 
required to score 3 mm sheet glass. It is always easiest to break the score if it is made 
along the centerline of the piece of glass. In other words, cut the billet in half, then in 
half again, to get the appropriate sizes to fill the mold.


Find the score line and break with big running pliers. Or hold the billet in a gloved hand 
and use a hammer to open the score by tapping on the back of the glass underneath the score 
line. (This does not take a lot of force; a tap exactly under the score line will cause the 
score to open cleanly.) Hold the billet low and over the table so it does not fall on your 
foot. Remember to wear eye protection.

Loading the glass into the mold:
Clean and dry the glass thoroughly, making sure to remove stickers. Any glass that is 
going to be lower than the thickness of final piece can be against the mold wall, but 
be careful not to indent the fiber paper because it will create a bump on 
the finished glass piece. Stack the rest of the glass into the center of the mold.


Loading the mold into the kiln:
Make sure the kiln is level and make sure the mold is level. Set the box mold on kiln 
furniture/posts, establishing three points of contact at least 2.5 cm from the floor of the 
kiln. This will allow heat to circulate all around the mold. If you would like to
intentionally create a wedge shape, you may set up the mold on an angle; but make 
certain that you have enough glass to cover the design elements, and that you adjust your 

annealing schedule to accommodate for the thicker area in the casting. If, for example, 
you would like a wedge that is 5 cm on the bottom and 2.5 cm on top, you will want to 
support the end that will be thicker on 2.5 cm kiln furniture, and the end that will be thinner 
on 5 cm kiln furniture, and then calculate the glass as if you were casting a rectilinear 
volume with a thickness of 3.75 cm.

Firing the piece
Vent the kiln at least up to 1100°F (593°C) to make certain that all of the moisture has
escaped the kiln. Plan to be present when the kiln is at casting temperature, and visually 
inspect the piece to make sure the casting is going as planned. If unwanted bubbles 
are present on the surface or just below the surface of the piece, plan to extend the hold 
at casting temperature until the bubbles have burst and healed.  Firing schedules provided
are specific to the Paragon GL24AD kilns that we use in our factory Research & 
Education department. All kilns fire differently. You may need to adjust the firing 
schedule for your specific kiln and project.  After the entire firing cycle is complete, we 
recommend leaving the piece in the kiln at room temperature for at least a day before taking 
it out to divest it.


Cleaning the finished piece
Remove the piece from the kiln and disassemble the box mold. Remember to wear an 
approved mask while handling the fired fiber paper and investment materials. Watch 
out for any sharp points if the glass has clung to the side walls of the mold.
The investment can be removed from the glass with a variety of tools, such as dental 
instruments, wooden picks, nylon brushes, and wood carving tools. Wooden 
tools are ideal for carefully removing broad areas of investment, and metal tools should 
be used delicately to clean fine details. A nylon bristle brush and forced air are also 
great tools for cleaning areas of residual investment. Most of the investment should be removed 
from the glass before submerging it in or scrubbing it with water. While water can be 
used to rinse away residual investment, we have found that scrubbing the glass with 
vinegar and/or CLR* breaks down the investment material.  Remember that you can create
a very different effect if you decide to coldwork and/or polish your piece. The optical 
qualities can change substantially, especially with coldworking on the edges.

How to use glass casting molds, tutorial

This tutorial came from GlassCampus.com and is full of excellent information.   Check out their website for many more informative tutorials!


Using Casting Molds

PREPARING THE MOLD
Carefully clean the mold to remove any dust and
scrub out any remaining kiln wash from previous
firings.  Single-use kilnwash like “Hotline” is
preferable to multiple-use kilnwash like “Bullseye”
because it’s easier to scrub out.  An old used
toothbrush is an effective tool for removing kilnwash
or a bristle brush on a Dremel will speed up the job.
Prepare the mold with 3 or more coats of thin kiln
wash.  More thin applications are better then few
thick coatings.  Be careful to not apply so much kiln
wash that you fill in all the detail in the mold.  Don’t
just coat the inside part of the mold that will be filled
with glass, but also coat the top upper surface.  Any
small pieces of glass that are left on that surface
will become permanently embedded into the mold if
you don’t.

FILLING THE MOLD
The glass level will drop as it melts into the mold.
Take care to be sure you  have enough to fully fill
the mold.  The smaller the pieces of glass you use,
the less it will sink.  On average, the finished
casting will be about half the depth of the loose
filled mold.  Because the glass level drops, you may
prefer to fill part of the mold with a pieces of glass
stood vertically to provide the extra glass needed to
fully fill your mold.

FRIT & POWDER
Glass powder and very fine frit doesn’t stay
transparent but will turn slightly opaque making the
finished casting looking more like alabaster then
glass.  Some attractive special effects can be
achieved by putting small amount of glass powder
in the details of the casting and filling with larger
pieces of a different colour.

FIRING SCHEDULE FOR CASTING (COE 96)
1. 800 dph to 1475°F hold 20 min
2. FAP to 960°F hold 30 min
3. 600 dph to 300°F OFF

FINISHING THE CASTING
Your casting will have some spikes along the
edges.  You can cold finish to remove them – either
by hand or with a grinder or wet belt sander.  The
casting will also have some texture from the mold.
You can remove the texture and smooth off the
scratches from cold finishing by turning the casting
over and returning it to the kiln to fire polish.

FIRING SCHEDULE for FIRE POLISH
      1    500 dph to 1000°F hold 20 min
     2  1500 dph to 1300°F hold 5 min
     3    FAP to 960°F hold 60 min
     4    500 dph to 200°F OFF min

The above firing schedules are for COE 96 glass.
For COE 90 add 20°F to all top temperatures.
For float glass add 50°F.

Video showing how to apply Boron Nitride Spray to a mold

This is a great video made by Colour de Verre Molds showing how to use MR-97 Boron Nitride Spray on one of their molds.  The spray is a great way to prime molds for firing without having to use kiln wash.  It is easy to use on steel molds, too!

Watch the video here!

Primo Primer video

We just happened to see this video today for Primo Primer.  If anyone is having trouble with either their glass sticking to their molds or if they are losing mold detail because of thick shelf primer, they should check this video out!  We use the pink colored Primo Primer so this new purple color is different!

View Primo Primer video here.

Another glass clay tutorial

Hi glass friends, we really liked this tutorial on glass clay so much that we thought we'd share it with more people! 

Glass Clay, a Step by Step Tutorial using 

Steider Studios Glass Medium

May 28, 2010

I’ve been asked often lately about making Glass Clay, so thought I’d give you a quick review:  what it is and how I make it.   I’m heading to Olympia next week to teach the Machine Embroiderers of Oregon and Washington how to make their own glass buttons with it.  I’ve taught this technique nationally since 2004, at the Art Glass Association Conference in Portland Oregon.  This is the first year in the last six that I did not teach Glass Clay (or Pate de Verre Without Molds) at the Las VegasGlass Craft & Bead Expo; I chose to offer a new class this year instead, while waiting to launch my new Medium.  By ‘launch’ I mean all that a new product entails, including packaging, labeling and marketing.  And after two years of research, it’s almost ready…almost!

Essentially Glass Clay is glass paste, another form of Pâte de Verre, but without having to make molds.  Certainly not a traditional technique, but a fun, easy, fast way to make small glass sculptures, buttons, beads, and more!

I make a clay-like substance, glass paste, by mixing powdered glass with a liquid binder or medium.  I prefer to use my new Glass Medium, which you will soon find on my website.  After testing many different materials my new Medium burns out cleaner than anything I’ve ever tried, while still being able to carve more detail into it after it’s dry and before firing.  Most people use CMC, and I’ve heard of and tested many other concoctions that may or may not work for you, but rather than go into them all I’m going to just tell you how I make it, using the best Medium I’ve ever tried.

I mix my Glass Medium with room temperature or warm tap water (if your water contains heavy mineral deposits, you can use distilled water, but it takes longer to set up…as long as a couple of days!):  Fill a clean jar with a cup of water.  Sprinkle in one teaspoon of Medium for a very thick paste.

Use a whisk or fork to stir until dissolved, then let stand 30 to 60 minutes to thicken, stirring occasionally.    I like it to be the consistency of jelly.  I have stored this new Medium in my studio for over two years after mixing, but typically it’s used up within a week.  I have used other binders that developed mold and just so you know, the mold adds an interesting patina.  If you prefer a less gelatinous mix, by all means thin it with a little more water.  Also, if you’re planning to use it for liquid lines, you’ll want to dilute it.

Wearing a respirator or N95 disposable particulate mask, place your glass powderinto a mixing bowl.  I prefer to use a small glass bowl, but often use a 4 or 8 ounce plastic food storage bowl.  Ratios of glass powder to Medium vary, depending on the powder.  Straight out of the jar glass powder can be as grainy as sand or as powdery as talc.

As a starting point I use 2:1, glass to Medium.  I’ll place 2 heaping spoonfuls of glass powder into my bowl, then drizzle 1 heaping spoonful of Steider Studios Glass Medium over the powder.

Using a palette knife or spoon mix well, mashing the Medium into the glass powder until it’s glossy.  It should be the consistency of cookie dough, or a wet pie crust, holding together when pinched or rolled into a ball.  If it’s too dry, your project will crack; add more Medium a couple drops at a time.  If it’s too wet, your project will sink down into itself; sprinkle more powder into the mix, a little at a time, mixing well after each addition.

Once it’s mixed to a consistency that feels like clay or cookie dough you’re ready to play.  You have about 30 minutes working time to sculpt it, make pattern bars or press it into candy molds to freeze, then it begins to dry out.

I mix all my colors  before beginning to sculpt, and wrap each with plastic wrap to keep it wet until I’m ready to work.  I can store glass clay like this for weeks and have left it for up to a year.  It can be a bit sticky, so I work on top of waxed paper to stay as mess-free as possible.

For sculpting I use dental tools, plastic and metal sculpting tools, plastic make-up applicators, toothpicks, kitchen implements and whatever happens to be close at hand.

I’ve made faces, flowers, animals, and small open vessels and bowls.  These small sculptures can be used for door pulls, plant and garden decor, adornment for lidded boxes and much more.

You can press glass clay into candy molds, freeze for an hour or two, then pop it out of the molds.  The advantage to using my Medium for this application (known as ‘freeze and fuse’), is you can ‘cold work’ the edges and carve in additional detail before firing, after the piece is completely dry.

One of my favorite ways of working with glass clay is making paste pattern bars.  Have you played with polymer clay?  Play dough?  I use the same principles.

Roll it out (or roll it through a pasta machine) between sheets of waxed paper & stack layers of different colors, then slice, re-stack and slice again.

It’s easiest if you roll between two pieces of waxed paper because it can be sticky.

Make what I fondly call ‘Pig in a Blanket’ by making a rope, then wrapping it with a different colored ‘blanket’ that’s been rolled out flat.  Or roll your pigs into many blankets for ‘rings’ of color when you slice.

Pattern bars are sliced with a tissue slicing blade, rolling the bar one quarter turn after each slice so you don’t end up with one flat side.  Use these slices for buttons, beads, cabochons, or as decor for other glass projects just to give you a few ideas.

Make coils or ropes of clay, place different colored ropes next to each other for millefiore.
More food for thought:  add mica! A little mica goes a long way.   Adorn with Dicro Slide! Use a cute scrap-booking punch to cut shapes from Dicro Slide that enhance your design and apply just before firing.

To get a spiral effect, stack rolled out sections on top of each other.

Carefully peel off the wax paper, keeping it close to your work surface.

Then roll it up, smooth out and slice.  The ends will be uneven unless you roll out rectangular shapes instead of ovals.  I slice off the ends, roll them into balls, pushing the colors into a marbled pattern, then flatten them for buttons and cabs.

The next step is to let your projects dry on paper towels.  Use a food dehydrator, or just set them aside for a few days.  In a one day workshop we use hair dryers to speed the drying process.  Once dry, glass clay is very fragile, like a meringue cookie so use care in handling it.  Gently peel off the paper towel from the bottom.  Using an emery board and wearing your respirator, file off any rough edges along the bottom.  Use a wooden skewer to sand off any rough spots in your details.  You can use a skewer or a dental tool to carve in additional lines if desired.  Just remember to take care as it’s fragile.  Did I already say it’s fragile?  It’s very fragile!

When you’re ready to fire, try to fire like sizes and like colors together.  For larger projects or light colors, your soak time will be slightly longer.  I strongly recommend using a kiln that you can watch the progress so you’ll know when to stop and anneal, and you can note the process temperature in your kiln.  Your pieces are going to shrink approximately 25 to 30%, depending on your process temperature.  The longer you soak at process temperature, the glossier they’ll get and the more they’ll shrink.  Vent your kiln until it reaches 1000º while the binder is burning out.  You can ramp up AFAP, but I think it’s better to control the ramp up; and do start peeking around 1200º to 1250º.  Be sure to wear your safety glasses when looking inside the heated kiln.  In my kiln, depending on the size and color, my process temperature is 1300º with a 30 minute soak for small two to three-inch sculptures; or 1350º with a 13 minute soak for beads and buttons.  I anneal at 900º, using Bullseye’s annealing_thick_slabs chart for thickness.

I love introducing people to working with glass powders, whether wet or dry.  I hope you found this post useful and I hope you’ll try my new Medium.  I have testers working with it now across the US and Canada, and am holding off my launch until all results are in.  An instruction sheet, including complete firing schedules are included with each jar of Steider Studios Glass Medium.  Available soon!  Very soon, I hope!

If you’d like to be among the first to know the release date, you can subscribe to this blog by clicking the ‘e-mail subscribe button’ at the top right of this page; or click on my Facebook Business Page (then click on the ‘like’ button to receive updates), where the announcement will be made.

Have Fun!  Be safe, wear that respirator and don’t forget your safety glasses!!  Oh, and I’d be ever so grateful if you’ll tell your friends about Steider Studios Glass Medium!

EDIT:  You can now purchase Steider Studios Glass Medium™ via Artfire……

Click here to purchase Steider Studios Glass Medium™ Economy Size on Artfire.
Click here to purchase Steider Studios Glass Medium™ Regular Size on Artfire.
Click here to purchase Steider Studios Glass Medium ™ Sample Size on Artfire.