Tuesday, August 25, 2015

Glass 3D Printer



I thought originally that this was a spoof or April Fool's Day hoax but it seems to be real! Very cool!!

"How hot does your 3D printer’s hot end get? Most low cost printers heat up to 240°C (464°F) at the most because they contain PEEK which starts to get soft if you go much higher. Even a metal hot end with active cooling usually won’t go much higher than 400°C (752°F). Pretty hot, right? MIT's new G3DP printer goes to 1900°F (over 1000°C) and prints optically clear glass.

By changing design and print parameters, G3DP can limit or control light transmission, reflection and refraction. The printer uses a dual heated chamber. The upper chamber acts as a 1900°F kiln while the lower chamber serves to anneal the structures. The print head is an alumina-zircon-silica nozzle.

There’s a patent filed on the process, apparently, and you can read the technical details in this thesis


and in some upcoming publications"

Apparently you could use Spectrum 96 or Bullseye 90 nuggets as the glass source so maybe one day....when the G3DP printer is less than $10,000!

Monday, August 24, 2015

Ted Sawyer

The Bullseye Resource Center (sic) recently published a video showing how Ted Sawyer produces his ethereal glass panels. I do like Sawyer’s work so thought I would see whether it was possible to reproduce.

Sawyer’s technique is essentially to sift layers of transparent glass powder onto clear sheets of glass and manipulate the powder with water, Glastac and clay modeling tools. He uses a lot of powder, a lot of layers and works on both sides of large 1m square panels so they need to be fused twice.

My first attempts were more modest – four colours on one side of 18cm square glass. My thinking was that if they did not work as panels I could slump them to make sushi plates. Two panels were disappointing and the other two (beach and nebula below) I framed in box frames with two cut mounts rather than a backing board. This means they can sit with a window or light source behind to show off the layers and texture.

The idea behind the technique is to create abstract patterns not only of colour but also of texture and transparency. There is nothing particularly hard about the techniques but it is the visualization of the finished effect that sets Sawyer apart.

The most fun was dropping water from a height onto the powder to produce craters that were then filled with another colour. I have to say that if that was the highlight then I wont be producing many more!

The other ‘problem’ is the long fusing schedule – almost 24 hours. Admittedly the schedule is recommended for a 1m square sheet but with a highest temperature of 693°C it is somewhat short of a full fuse. This means that some of the texture is preserved but because the powder does not fully fuse some of the transparency itself is lost.

I know that I am not as gifted as Ted Sawyer but I would rather run a kiln full of pattern bars or work 6 layers deep if it is going to take 24 hours.

Vitrigraph - Fun with Molten Glass

I added a Skutt Firebox kiln to my studio a while ago for hot combing and vitrigraphy but have only recently found a suitable stand for the latter. I had thought of using two tables and some concrete blocks to raise the kiln up but it was never going to work in my studio (ie the laundry!!)

Finally I bought a set of stainless steel shelves from Brayco. The uprights are 1.8m and the kiln sits on a shelf 1m above the ground. The central section of the shelf is cut out to allow the glass to fall onto a second shelf holding a stainless steel bowl.

The kiln base is removed and placed on a piece of 2.5cm fibre board with a 2cm hole cut in the middle. The scrap glass is cut into 2cm squares and put in a 15cm terracotta pot (the expensive Italian one) and the pot is put on two mullite strips to raise it off the fibre board. For the first run I did not enlarge the (drainage) hole in the pot but it might be worthwhile for the future.

I chose to use an ultra conservative firing schedule – 

1 hour to 320°C

4 hours to 740°C

1 hour to 1040°C at which point glass began to flow.

The Firebox doesn’t have a programmable controller and the ‘heat’ switch is described as ‘infinite’. That means at setting 1 ½ the element heats at about 180°C per hour and 300°C at setting 4. The switch design means a lot of trial and error and I figured I would rather go slow and steady to avoid stressing the terracotta pot more so than the glass.

Recommended schedule is 250°C per hour to 940°C (about 3 ¾ hours). The thermocouple pyrometer though is reading from close to an element and the glass in the terracotta pot is insulated. Next time I will try to try 250°C per hour for 4 hours and see what happens.

When the temperature reaches 940°C the glass is molten and starts to flow through the pot’s hole. The temperature has to be raised and lowered to get the glass streamers to thicken and thin. I used some steel salad servers to manipulate the streamers and scissors to cut the flow. The streamers fall into the steel bowl filled half full with vermiculite. The streamers don’t need to anneal but the vermiculite gives some insulation to slow the cooling somewhat.

The great things about a vitrigraph kiln are that you can make customized elements for use in other work and use up scrap glass in any colour combination you like. I used Spectrum 96 white, cream, grey and pink as I wanted to produce elements that resemble ghost gum bark. It is also a way of using a kiln to replicate what is usually done in a hot glass studio so you can produce rods, stringers and murrini rods.

So, all in all a great trial run and I will definitely be doing it again.

One technique for the future would be to let the molten glass to flow straight into a steel bucket of cool water. The glass should fracture from heat shock and create customized colour combination frits.