Dean's Blog: 2006

Wednesday, December 20, 2006

Fusing Glass

Introduction

Let's face it, I'm obsessed with glass. I've made stained glass for years, and I built miniature studio in my garage so I can make torch-worked sculptors.

Fusing, and slumping is one of the few glass art forms I haven't yet tried.

Having no previous experience in fusing, I decided to take a class at the Bay Area Glass Institute (BAGI):

What is Glass Fusing?

Fusing is the process of heating multiple pieces of glass in a kiln to form one unified piece. Heating the glass just enough to join, but while still retaining the original shape of the individual pieces is called a tack fuse. Heating the glass enough to form one seamless piece is called a full fuse

What is Glass Slumping?

Slumping describes the processing of reshaping a piece of glass by heating it, and allowing it to fall into a mold (form).

Instructor

My instructor, Janett, has an amazing knowledge of not only glass fusing, but also torch working, glass blowing, and stained glass:

Tools

Here's the tools of the trade:

Not all glass is appropriate for fusing. Glasses which expand, and contract at different rates will indeed fuse, but then crack as they cool. Bulseye glass is the most popular as it comes in a wide variety of colors, and styles.

Kilns are basically big ovens which can reach about 1600^o

Glass cutters are used to create scores, and direct glass to crack along certain lines.

Fusing glue hold the glass in place before it is fired.

Kiln shelf

Kiln wash

Applying kiln wash

Fusing is typically done on a large flat unfinished ceramic kiln shelf.

Kiln wash is basically glass Teflon. It keeps the glass from sticking to the shelf.

First Project

Glass fusing is deceptively simple: Cut out pieces of glass, arrange them, and pop them into the kiln. Here's my first project:

Red circle of glass	Cut-up circle of glass	Into the kiln
Fused circle

But there are any number of things that can go wrong. Molten glass flows -- sometimes in unpredictable ways. Fire too long, and the glass will spread out, and then contracts back leaving uneven borders. Fire too short, and you'll get lumpy glass. Some glasses melt faster, and spread out when fired; others tend to stay put. And many types of glass don't fire true -- i.e. change color when fired. To help out us neophytes, Janett created this pallet of pre- and post-fired glass:

Second Project

Here's my second project. On the bottom is a layer of clear glass. The second layer has red on the edges, stripes of black, and more clear in the center. On top of that is amber squares, and sparkling green stringers (thin rods of glass).

Before fusing

Fused, and slumped

Julie's Projects

Here's a few projects made by my classmate Julie. The piece below is made of three layers of glass, giving it great depth. Some of the squares almost appear to float.

Here's very simple, but elegant design:

Big Tools

One of the cool things about BAGI is their equipment. I grew up with a garage full of lathes, acetylene welder, and drill presses, so I found BAGI's collection of over-sized glass grinders fascinating:

Belt grinder

Bench grinder

Disk grinder

Holiday Sale Items

BAGI is a nonprofit organization, and every year they have a Holiday Sale. Artists donate pieces, and the proceeds go to BAGI. These are amazing. I guess it's always good to have something to work up to ...

Holiday Sale

Conclusion

I've seen a lot of fused glass at art shows -- much of it monumentally bad. From this I assumed any yo-yo could fuse. But it's more complex than I expected. There's a lot of technical gobbly guck: coefficient of expansion, annealing/fusing/tacking temperatures, devitrification. There are four types of clear glaze that melts at different temperatures. There's dozens of types of glass: transparent, opaque, streaky, iridecent, textured, dichroic, two types of black, and 19 types of clear!

But it's not that hard either, and it is great fun.

Thursday, October 19, 2006

LED Christmas Lights

Recently I bought a set of LED Christmas lights from All Electronics:

These lights are sold as-is because the controlling units overheats. So why buy a known-defective set of Christmas lights? To fix them, of course! These lights are controlled by a programmable chip called a PIC. Careful programming can significantly reduce the power consumption, and fix the heat problem.

What is a PIC?

A PIC is essentially a one-chip computer designed for embedded systems. You can't play video games on it, or even run Windows. It's made to run very simple tasks. A typical PIC only has a few hundred bytes of RAM.

Replacement PIC

The PIC that comes with the LED lights is a write-once device. It can't be modified. Fortunately there are a number of programmable replacements. I choose the PIC16F627a, mostly because I already had several on hand. They're available at mouser.com. for about $1.75.

Original: PIC16C54 (CF745)

New: PIC16F627a

Tools

Writing code into a PIC requires a programmer. Removing the original PIC part requires a soldering iron, and a solder sucker (remover).

Warp 13 PIC Programmer

Soldering Iron

Solder Sucker

Adding a Socket

The LED controller comes with a 18-pin DIP (through-hole) PIC soldered directly into the PC board:

To ease development it is best to remove the original part, and install a socket:

Desolder PIC

PIC chip removed

Socket

Hardware Programming Model

Eight bits (signals) are used to control LED illumination. Four bits are used to select each LED color (red, yellow, orange, and green). Four bits are used to select a bar or arm of the star (e.g. all LEDs on the horizontal axis correspond to bar 3):

An LED will illuminate if both of its bar and, color are selected. Thus, selecting red, and bar 1 will light the two LEDs on the vertical axis:

The following diagram shows the control signal to PIC mappings:

Software

Originally I had hoped to read the software from the original PIC, and then modify it for my purposes. But the PIC16C54 is an unusual part, and my programmer can't read it. So I decided to write everything from scratch.

Pulse Width Modulation

This code uses one of the PICs timers to create pulse width modulated signals. To prevent the unit from overheating the power consumption must significantly reduced. A common trick to reduce the brightness of an LED is pulse width modulation (PWM). Basically this means turning the LED on and off very rapidly -- so quickly it is undetectible to the naked eye.

The brightness, and power consumption are adjusted by changing the duty cycle (percentage of time spent on).

Algorithm

Here's a highly simplified version of the code, written in 'C':

pseudo_code.c

Source Code

Here's the real assembly code:

xmas.asm

Conclusions

The power reduction was a success. The lights used to draw a maximum of about 1.8 amps; now it's down to about 430 milliamps. It doesn't get warm even after hours of operation.

Writting display patterns is pretty easy. But because of the limitations in the hardware, there just aren't that many interesting designs you can create.

Here's a video of the lights in action (4MB):

xmas.avi

Thursday, September 28, 2006

Making Sushi

Sushi Chef Neophyte

Making good sushi is no trivial matter. People study for years to become master sushi chefs. And my particular style can best be described as survival cooking. However, making sushi is 50% arts, and crafts. And for some sick reason I enjoy doing meticulous, detailed work. Still, I expected my sushi to look like it was " hacked to death by a blind woodsman."

Tools

Making sushi doesn't require too many exotic tools:

Bamboo mat (makisu)

Sharp knife

Rice cooker

The one key item is the bamboo mat (makisu); it helps keep the rolls even.

Real sushi chefs use special knives, which are only sharpened on one side. My personal opinion is that any sharp knife will work.

Ingredients

California rolls are usually made with avocado, and fake crab. I use smoked salmon mostly because it keeps for weeks in the refrigerator.

Smoked salmon

Avocado

Nori (seaweed)

Sushi vinegar

Black sesame

The salmon, and the avocado need to be sliced into thin strips:

Sliced ingredients

Rice

The preparation of sushi rice is more complex than most people imagine. Traditionally the rice is soaked in water to soften it, then cooked with a piece of seaweed (for flavor). A mixture of vinegar, salt, and sugar is poured over the hot cooked rice, and then fanned until shinny and cool. Experts use a bowl made of bamboo. I use an 13x9 baking pan and an electric fan.