Second Approach to Kiln Casting

I have created slabs with cut out shapes for another method of kiln casting.

This is a second approach to kiln-casting with molds. Instead of making plaster molds, the slabs will serve as a mold for the glass to slump through.

Here, I will use the slabs as molds to slump glass on top of. Once I have bisqued the slabs, I applied kiln wash to two of the slabs to test if it prevents the glass from sticking to the ceramic mold.






Setting up the molds: Here, I have cut the glass to the proper size of the mold. The glass is placed on top of the mold.




(white pieces have been applied with kiln wash)

The molds are set up in the kiln on stilts so that the glass has enough room to slump down

Result of Molds

Once the plaster molds have set up, I dry them out in a heat box, so that all the moisture is removed from the plaster. These molds are now ready to be kiln-casted.

Measuring the cut out shape's volume in cubic inches, I am able to determine  how much glass to use.

I have stilted a terracotta flower pot above the mold to drip or pour the glass into the mold. Once the glass reaches temperature, it will melt out of the hole at the bottom of the flower pot and drip into the mold. 

Making Molds

The cut out pieces from the ceramic vessel are embedding into a block of clay at the leather hard stage. Leather hard is a specific stage where the clay is visibly damp (dark gray in color) but hard enough to work with without damaging the piece. I have made sure that there are no undercuts where the plaster will seep into, preventing the piece from becoming trapped in the mold. I am using cottle boards to block of the diameter of the mold so that when I pour the plaster inside, it will contain its shape. Before pouring plaster in, I have to make sure there are no cracks for the plaster to escape by filling every corner with a little coil of clay. I then apply mold soap to the entire piece, including the cottle boards in order to prevent the plaster from sticking to the piece.









After the kiln cast plaster is poured in, I leave it over night to set up.

The plaster I am using is a very specific plaster used for kiln casting and slumping glass. These molds will be able to withstand the temperature of the glass once it begins slumping in the kiln.

Kiln-fired glass can be done in a ceramic electric kiln between 1300-1500 degrees F, which is lower than ceramic temperatures. 

Starting Fall Semester: Kiln Casting

Design: Glass sliver in the middle of the ceramic bottle so you're able to see through it

Sketches of bottles meant for olive oil. My plan is to throw the ceramic bottle and cut out shapes for the glass to fit into. The glass will serve as a "window" to see the liquid inside the bottle.

Thrown vessels with cut outs.

Glass will replace the cut outs

I will make molds of each of the cut out pieces, in order to cast glass into. Then, I will fit the glass into the ceramic vessel.

The vessels have been bisqued and glazed to cone 6.

I have created and tested several cone 6 glazes in order to get a cone 10 atmospheric effect, without having to use a fuel burning kiln, in order to preserve elements and electricity.

"Cone" is a measurement of temperature over time or "heat-work". A cone is placed in the kiln during any type of firing, bisque or glaze, in order to regulate the proper amount of heat and energy. Instead of using a gas kiln and firing to cone 10 at a temperature of 2381 degrees F, I am trying to achieve the same cone 10 effects while firing to cone 6 in an electric kiln, at a temperature of 2232 degrees F. 

Working With Color

This week I have been focusing on form and color. So far, I have been using clear glass, however, now I am starting to add color to my work. Silica, or sand, is the main ingredient in glass and it is able to move with a flux and soda ash added to it. Glass coloring can be obtained by adding different colorants such as iron, chromium, cobalt, and manganese. Color is manufactured into rod, frit and powdered forms and can be applied in several different ways. Each color is made up of different properties. Blue, green and purple colors are considered “soft” glass, as they are easily manipulated and heat quickly in the furnace. The clear glass that I have used so far melts fairly quickly and drips easily. Red, orange and yellow colors are considered “stiff” because they take longer to heat up and hardens quickly while out of the flame. Working with color is a challenge, especially when you are mixing soft and stiff colors together in a piece. I have experimented with using an aqua glass and a red glass which gave me more of an understanding of how to work with colored glass. I have also started to combine the two colors. This has been a challenge as the blue melts a lot quicker than the red, which is hard to control and heat evenly. I have tried picking up color on the marver as well as in the furnace. Working with color has taught me a lot about control and heat. I am playing around with shapes and experimenting how much I can manipulate the glass, such as swinging the glass, letting it hang, pulling on it, and using wood to shape it. I have learned a lot this week through using color and want to experiment using more colors. The color aspect of glassblowing teaches me how technical this material really is. I am interested in making functional pieces, such as planters, combining both glass and clay. This next week, I will attempt to blow glass into ceramic vessels.

Practicing Basic Fundamentals of Shape and Form

Bottle

This week I am focusing on practicing the basic fundamentals of glassblowing. I have been blowing marbles, bubbles, and cups. Emphasizing learning and practicing the fundamentals of glass is essential in knowing how to develop any artwork. Understanding how the glass reacts to heat, pressure and control is extremely important. I have learnt through ceramics that repetition will allow you to perfect certain skill sets and achieve the work you envision. Shaping marbles, blowing spheres, and practicing punty’s has helped me in understanding the fundamentals of glassblowing and will improve my work as I start to go on to making functional pieces. I have learned how to gather sufficiently and maximize my time while being in the hot shop. Timing, temperature and control are all extremely important factors of glassblowing. Knowing how to efficiently maximize your time working with the glass will allow you to be able to achieve the shape and form you intend. I am learning how to work the glass with the right amount of heat which helps me shape it properly and resourcefully. I have been practicing punty’s, which is when you gather a small amount of glass from the furnace and shape it on the marver, in preparation for attaching it to the end of the glass piece. You have to be aware of how the temperature affects what you do. If, for example, you are making a small, delicate and thin cup you will need to make the punty with a very small gather of glass on a small rod. I have repeatedly practiced puntys and blown spheres this week and have improved each time. This allows me to understand what to do in order to make a cup or bowl. All of these steps will allow me to go forward in making more complex pieces. While practicing the fundamentals of glassblowing, as well as understanding how the glass reacts under different circumstances, I have found a lot of similarities between glass and clay. Both glassblowing and throwing on the wheel are extremely alike in that they both require keeping the piece on center, keeping an even wall thickness, understanding how to shape the piece and how to control timing. I believe my background in pottery has helped me understand more about how I should work with the glass. This week has been a lot of repetition and practice but it will help me improve quicker and more efficiently for the future. 

Coldworking

Lap Grinder

Before the surface is coldworked

After the surface is coldworked     

This week we have been working on coldworking techniques. Coldworking is what you do after hotwork, or glassblowing, in order to improve your work. Coldworking describes a great variety of processes in which glass is removed from the surface of an object with a scratching, grinding or chipping procedure. Using electrical equipment, such as grinders, laps, and wet belt sanders which are specifically made to work wet to avoid the glass catching on fire. For our coldworking process I used the Rotary Lap Grinder. These machines use Silicon Carbide coated or diamond discs to grind and polish glass. This machine also sprays a jet of water to the center of the disc so it spread all the way out as the disc rotates. Most machines use either a Velcro or magnetic hold to attach the diamond discs to make it easy to change from one grit to another. As I grinded the chandelier pieces we had made, I had to make sure the piece was evenly balanced the whole time on the wheel to ensure it was level  and flush, occasionally turning the piece 180 degrees so the disc hits all sides of the piece. I grind the glass in one direction, so all the scratches created by the grit are in the same direction. I then move on to the next stage while using another disc with a finer coarse grit, grinding the glass across the scratches. Here, the finer grit has removed the coarser grit grind. After we’ve achieved the smoothness we want, we go on to polish. We move to a softer pad and pour some Cerox mixture, a rare earth based powder, onto the disc. Cerox is suited for high production polishing where extremely bright finishes are required. Although you work only in one direction to grind, it is important to move the glass around as you polish. I also learned about beveling sharp edges, although this process wasn’t necessary for what needed to be done for the chandelier pieces. Being a ceramics major, I had a little understanding of how to bevel and what it did for the piece.  A sharp 90 degree edge is very fragile and prone to chipping. The bevel prevents chipping from trivial trauma and the bevel actually makes the edge look more finished and smoother. You’re not completely finished after you blow glass and place it in the annealer to cool down. Coldworking is essential for giving your piece a smooth touch and finished look before assembling.

Interning at Zen Glass, St. Petersburg, FL

I have started interning for Zen Glass in St. Petersburg, FL and so far I have been observing several glassblowing techniques from assisting Christian Zvonik in the hot shop. For the first few weeks we focused on production skills. So far, I have helped Christian in making chandelier parts, wall plates and bird sculptures. I have learned how to be quick and efficient in working with a material that requires constant heat and conforms to the laws of gravity. Each chandelier and wall plate were made one after another, and placed in the annealer (oven designed to cool glass) to cool slowly overnight. I have also learned glass mold-making skills for production purposes as well. We have made well over 700 glass pucks for mason jars. These pucks are used to keep foods and liquids in the mason jars air tight. I was also responsible for packaging them into boxes and shipping them out the following day.

Every second Saturday in St. Petersburg is an Art Walk for the local art community. This previous second Saturday, June 14^th, I assisted Christian in providing demonstrations in the hot shop. We made several chandelier parts and a few owls for the audience. In assisting Christian, I am responsible for gathering the molten glass with a hollow steel tube, or blowpipe, from the furnace. The molten glass in the furnace is about 2,025 to 2,125 degrees. Gathering glass requires continuous rotation of the blowpipe in the furnace, in order to gather the glass steadily and evenly. I then take the glass to a steel table, called the marver, to begin shaping it. Even once I’ve achieved a cylinder, constant rotation of the blowpipe is extremely necessary to prevent the glass from dripping off. We have to create an even-walled bubble as we blow the first bubble to keep everything centered. Constant rotation and heating of the glass in the glory hole (oven that reheats the glass to keep it malleable) is extremely important. I set up frit (crushed up glass) on the marver for Christian to roll the glass on to achieve color. After Christian shapes the piece on the bench, I blow air through the pipe and into the glass. As Christian starts to shape the piece, I use a wooden panel to square up the shape of the lip and block his arm from the heat. I am responsible for opening the glory hole doors as Christian heats up the piece. Once the shape is achieved, we transfer the piece to another rod called the punty. After the final shaping and gathering of heat, we crack the piece off the pipe, using a wet tool to etch a line across the neck. This weakens the glass and we are able to tap the pipe, releasing the piece. Wearing special heat resistant gloves, I catch the piece and run it over to the annealer to cool down. Now that the pieces are finished, they are ready to be coldworked. I will be introduced to the basics of coldworking which is the grinding and polishing of the glass in preparation for assembling work. I have learnt a lot this previous month about how to keep the glass centered and the steady consistency this material requires. 

Blowing Glass Inside Ceramic Pot: Second Attempt

Ceramic forms before blowing glass inside
Pot on the left is coated on the inside with kiln wash

The first two cracked like I had suspected. So, for the next two, I set the annealing temperature to 1285 degrees. This would give the ceramic a chance to draw out even more moisture and get to a closer temperature of the glass that was being blown into it.

The second time was more successful. Only one piece cracked and the other one survived. I continued this once more and had the same results. I am researching the difference of coefficient of expansion between the glass and ceramic as they shrink and cool and different rates. I want the glass to stick to the ceramic without it becoming loose. I am thinking about mixing my own clay body in order to get better results with the annealing of the glass. I will make my pots thinner next time so that it heats quicker and is able to adhere to the glass more efficiently. This experiment was a great learning experience. I was aware that the pots would probably crack and knew that this would be a long process of experimentation and research. I am interested in making functional and sustainable planters. I will continue to experiment blowing glass into ceramic vessels without focusing too much on the form or shape at first but more on the technical aspect of getting the two materials to amalgamate together into one, coefficient piece. Once I am able to make the two materials work together, I can then focus on the design aspect. I will continue to experiment with this process while trying out several different techniques.