April 25, 2010
Almost recovered from my most hectic spring schedule ever, and way behind in blogging.
I want to share my article published in Glass Craftsman Magazine, about organizing glass powder colors for those of you that missed it. It’s my way of keeping powder colors organized and readily available for choosing which colors to work with in any given project.
Without further ado:
How to Make Powder Color Charts for Glass Fusing
I would like to introduce you to a method I’ve developed to organize all your powdered glass into easy-to-use fused bars of color that make up samples for each color “family”. This method will give you color charts that are economical, quick-to-update and will give you a great amount of information in a small amount of space. Having these useful Color Bars in your studio will make it easier for you to select which colors of powder to use and how much powder to apply in any future kilnformed project.
In my work, I use powders extensively and have developed this quick method that I call “Color Bars”, an at-a-glance method that has shortened the amount of time I spend making up color samples for each of my fused glass projects. I knew that the amount of powder I applied before fusing made a big difference in color saturation of the finished piece, and that the fired color could be different from the catalog image. I needed an all-encompassing set of color samples that was economical as well as space-saving for my small studio. I decided to make narrow one-inch-wide bands of color that would have all the colors I use in each color family on one bar. You might choose to organize your bars in a slightly different way, depending upon the palette you use and the available space in your studio.
What you’ll need:
-Powdered glass: all the colors in your collection of powders. It is helpful to arrange them ahead of time in the order you’ll be applying the colors. You will probably want to separate the transparent powders from the opals.
-Sheet glass: Fusible glass in clear, white, black, and if desired, French Vanilla (to test for color reactions that can happen in kiln work), all cut into 1” wide strips.
-Glass cutter and pliers
-Paper template marked into a grid of 1” squares that is as wide as your longest bar and as long as the number of color bars you want to make at one time.
-Respirator or disposable particulate respirator (N95)
-Small enamel sifter
-Stabilo or Sharpie pen
Organize your colors:
If you don’t have every color of glass powder available you can simply make your color bars with what you have on hand. As your collection of powder grows you can update and expand your color bars. Arrange all the colors in your powder collection from light to dark and separate them into color families. This will show you how long you will need to make your strips of base glass for the sample bars.
You may find it helpful to make a paper mock-up of the color bars as a visual cue for where you want the individual colors to go before you don your respirator. Using the manufacturer’s catalog, simply select images of all the colors in your powder collection, then cut out the images and paste them in the correct order onto a strip of heavy paper that is cut to the length you will make that sample bar. I use Bullseye Glass but you can do the same with glass from any manufacturer.
Tip: I made color bars on top of white, black (opaque powders only), French Vanilla and clear sheet glass. The clear base allows me to “audition” each color of powder over any color of sheet glass without having to make a sample of that particular combination. The French Vanilla base gives me a good color reaction chart for each color. Remember, transparent colors will show vividly on white, French Vanilla and clear base glass, but they will not show at all on black or dark colors. For that reason I don’t use transparent powders on the black bases.
Tip: I combine color families to make a longer strip when necessary to keep my color bars as uniform in size as possible, and to avoid numerous small lengths that could potentially get lost on my work surface.
Preparing the base glass for a Full Fuse set of Color Bars
Cut your one-inch strips of sheet glass into lengths according to how many colors there are in each of your color “families”.
These color bars will be taken to a full fuse, so your sheet glass base must be two layers thick to avoid distortion of the shape. Cut, clean, and glue all the strips of base colors in the lengths you have determined you will need. To evenly distribute the powder in one-inch segments of color, place your glued two-layer glass bases on top of a one-inch grid, or mark off lines spaced one inch apart with a Stabilo® or Sharpie pen®. Align each of the separate base colors for each color family, long sides touching so that you can sift one color of powder across all the base strips at one time. Sifting the powder over your aligned strips in this fashion is quick and gives you a more accurate layering of powder on each base.
In order to give yourself as much information as possible in a one-inch space, it is important to use the powders in a variety of thicknesses on your base strips. Start by sifting as thin a line of powder (one pass) as you can across the widths of the set of strips using the line sifter. At the opposite side of the one-inch section, again using the line sifter, sift a line as thick as possible, usually 1/8 inch high. In between those two lines of sifted powder, using a small enamel sifter, distribute the powder creating a graduated application of powder (thicker on one end than on the other). This graduation will give you a quick reference at how varying thicknesses of powder will appear when fired. Be consistent in your applications, moving from thin to thick layers across all the colors.
For the blue family, I made up two sets of bars. One set for translucent colors had three bars – white, clear and French Vanilla; and one set for opaque colors had four bars – white, clear, French Vanilla, and black.
I cut my 1-inch strips eleven inches long for my translucent colors to accommodate the eleven different blues I currently have in that collection. I arranged the turquoise blues separately from the other blues, and applied each of them from light to dark. For the opal colors I only have seven blues in my collection, so my strips were cut into seven-inch lengths.
Tip: To render a wider range of saturation within each color you can lengthen the color bars to allow a 2-inch long section for each color. Note however, that this will double the total length of each color bar.
Continue making your color bars in the same way until you have made color bars representing all the colors of powdered glass you have in your collection. Carefully pick up each sample bar and put it on a freshly-washed kiln shelf with adequate space around each piece. Load your kiln in your usual manner and fire according to your usual firing schedule for a full fuse.
Suggested Firing Schedule:
400°F per hour to 1100°F, hold for 20 minutes
400°F per hour to 1485°F (or the full fuse temperature of your kiln), hold for 10 minutes
AFAP (as fast as possible) to 900°F, hold for 60 minutes
100°F per hour to 700°F, turn the kiln off
Process Temperature Color Bars:
A second set of color bars can be made to show you how process temperatures affect each color of powder. For this set, apply the powder in the same style of graduated thicknesses as the Full Fuse sample set, using the same color placement.
You can use a single layer of clear glass for your base because we won’t be firing to a full fuse, therefore we have no volume control issues.
I cut 9 bars from my one-inch strips of clear in the length I need for the colors of powder I have. After lining them up, long sides together on top of my gridded paper, I apply the powder in graduated thickness. Next I fire each strip at a different process temperature, holding for 10 minutes at each temperature; then anneal the glass as usual. These tests tell me how the powder colors differ at each process temperature with the same holding time. It can be painstakingly tedious to make and fire these sample bars, but I find it is well worth the effort.
Firing schedules are the same as the previously suggested schedule for each of these bars, but with a different process temperature for each. I made sample bars with the following nine process temperatures, and held each of them at that temperature for 10 minutes:
1250°F, 1275°F, 1300°F, 1325°F, 1350°F, 1375°F, 1400°F, 1425°F, and 1450 °F
(note, in my photo I included 1225 as a process, but in my kiln that wasn’t hot enough for the glass to fuse.)
Why the Color Bars Work:
I used to fire each powder color onto two one-inch pieces of sheet glass and glue one to its jar while the other would ‘float’ around in my studio so I could “audition” it next to other colors. When it was time to open a new jar of powder, I’d have to pry my color chip off the empty jar and re-glue the sample to the new jar. My little one inch chips of ‘floating’ glass would become lost in my work area. These Color Bars are substantial enough that they don’t get lost and I can still audition colors next to each other. I keep my color bars near my powdered glass (which is also arranged in color families) making it easier to select colors for any given project.
Edited by Judith Conway for Glass Craftsman Magazine, Issue # 216 – 4th quarter 2009