Northstar Glass Frit
A note from Northstar!
As with any new glass, please test all glass colors for compatibility in your specific application before making an extensive piece or production run.
Northstar Glassworks, Inc. strives to make all of our colors compatible and easy to use. However, it is not possible to make all colors exactly the same C.O.E. Some colors may check if used in combination with other colors under under certain applications.
USING NORTHSTAR BOROCOLOUR COLORED BOROSILICATE FRITS & POWDERS
The term "Frit" refers to granular crushed glass. Soft glass frits have been available to glass for a long time in many colors and several different mesh sizes. Furnace working glassblowers and European style Lampworkers use frit regularly as a means of adding color to their work. Frit can also be used in such techniques as Pate De Verre and Fusing. It is possible to crush and screen your own frit from rod. However, this is a difficult, messy and time consuming task. We offer many of our borosilicate colors in frit (course grit) and powder form. These frits and powders have been formulated for use with Pyrex, Duran, Kimax, Northstar or any other glass with a similar coefficient of thermal expansion (32 +/- 2). Using frits and powders provides the hot glass artist with a means of adding color and/or texture to artwork quickly and easily.
As with most other materials, there is no "right way" or "wrong way " to utilize frit. Experimentation will lead you discover your own unique effects and subtle refinements of technique. Here are some suggestions.
The basic idea is to get frit to stick to a target object. In order for this to occur the temperature of the object must be hot enough to be soft (at least on the surface of the glass).The hotter\softer the target object is, the more readily the frit will stick to it. If the object has already been formed and slumping is not desirable it is better to heat the object just enough for the frit to begin sticking (by preheating the frit in your oven, the target object can be slightly cooler and therefore less likely to slump). Successive layers can then be built up if a heavy coating is desired. A light sprinkling of frit may be used as a subtle highlight of brightly colored dots or a substantial layer of color can be built up giving a more uniform look.
Frit can be coated on the outside of solid or hollow objects. It can also be coated on the inside of hollow forms. Frit may be fused in completely or left partially raised for a surface texture. Different colors may be mixed for a custom look. Clear frit (NS-100) may be added over a colored object for effect. A sprinkling of frit may also be mixed into the body of a solid glob of glass, giving the entire glob color.
After first heating the "target object" hot enough so that frit or powder will stick to it, here are some possibilities:
1) SPRINKLE METHOD. Frit or may be sprinkled over your object either with a spoon or with the fingers. When using this method it is wise to place some kind of clean plate or container under the work area to collect any frit that does not stick (invariably, some frit will not adhere the first time). Remove the object from the flame before sprinkling frit. Sprinkling directly through the flame is not recommended since the flame will blow some of the frit away. This is not only a waste of good frit but cause a dust problem in your shop (see health precautions below).
2) DIP METHOD. Another method is to put frit in a bowl and then dip the targeted object into the frit. The piece may be rotated so as to be coated evenly. Repeat as many times as necessary for the desired effect.
3) TUBE METHOD. Frit can be fused to the inside of a hollow object by sprinkling it into a rotating tube. Using this method the frit may be added either before or after the object has been heated. This method can also be used when applying frit to tubing in a glassblowing lathe.
4) ROD METHOD. A clear or colored rod may be heated (usually the tip) , coated with frit (dip method), and then applied in a usual manner. This is a very quick and easy method of adding color.
WORKING FRIT OR POWDER IN: Once the desired amount of frit has been deposited onto the object, use a relatively cool flame to fuse the frit in. Use a cool flame because the small particles of frit, until they are mostly fused in, are little bumps on the surface of the glass, easily caught by the flame and super heated to a boil, which could cause a rough texture. A hot flame may be used but the object should be passed quickly through the flame so as to heat the frit more gradually.
EXOTIC FRIT OR POWDER CAN BE USED FOR A METALLIC FUMED EFFECT!
If a particular size particle of frit is desired for a specific project it is possible to screen the frit. Simply find a piece of screen (any kind of screen will do, stainless is the best) of the desired mesh and filter the frit through.
CAUTION: AVOID EXPOSURE TO GLASS DUST. ALWAYS USE APPROPRIATE HEALTH AND SAFETY PRECAUTION
USING NORTHSTAR BOROCOLOUR BOROSILICATE COLORGLASS rev 97-A
Northstar is a colored borosilicate-type glass rod. It is compatible with, and may be combined with Pyrex, Kimax, Duran and any other glass with a similar coefficient of thermal expansion (32 +/- 2). Glassblowers and Lampworkers will be able to achieve satisfactory results with Northstar glass upon the first try. However, Northstar glass upon the first try. However, Northstar glass has some of these characteristics with which the glassblower may not be familiar. It is our purpose to explain some of these characteristics so that the glass artist may attain the most exciting effects possible. Also, some of the following notes will be of more interest to the advanced artist trying to achieve a particular effect.
Northstar is currently available in 54 colors in rod and 24 colors in frit and 22 colors in powder form. Some of these colors are affected by heat. We call these "striking" or "re-heat" colors for they change color when reheated (i.e. Yellow is in clear glass rods when you receive them from the factory. But when heated to the annealing temperature [about 1050 degrees Fahrenheit or 550 degrees Celsius], they change or "strike" to their new color). Other colors may appear blue, green or amber before striking. (ALL RUBIES are now shipped pre-struck to insure color quality.) The longer you strike a color, the darker the color becomes until the saturation point is reached . If, after striking, the glassblower heats the glass to the working temperature again, Northstar returns to it's original un-struck condition. This process of striking and reworking may be repeated many times. The transparent colors are obtained more easily if struck in an electric kiln.
Work your piece as hot as possible (but do not boil) and place it in your annealing oven while it is in the un-struck condition. Striking may be performed in your torch flame as well, preferably in a neutral to slightly oxidizing atmosphere. Avoid striking the glass at too high a of a temperature. Using either method observe the glass while it is being struck. It is possible to control how dark your pieces become by carefully controlling the striking time. The striking process may be performed simultaneously with the annealing process.
Please note: Some colors will strike at slightly different rates. For example: Orange will take longer to strike than Ruby. If you have many different colors in the same kiln this can cause the Ruby to become darker than you want while waiting for the Orange to strike. If this is a problem, you can strike differently colored pieces in separate firings of the kiln, or if you are using many different colors in a single piece, keep watching during the striking process and begin to cool the piece when you are satisfied with the effect.
Another important consideration when using Northstar is the oxidation/reduction balance of your flame. This is the ratio of oxygen to propane gas in your flame. Some colors turn out better in an oxidizing flame, while others turn out better in a more reducing or neutral flame. Most colors look great using either flame. Basically a "hissing" flame with the oxygen turned way up, almost blowing the flame out, would be considered a very oxidizing flame. On the other hand, a soft bushy flam low in oxygen, is a reducing flame. A neutral flame is somewhere in between. Only practice and experimentation can teach a glassblower the subtlety of this concept. In general, if in doubt use a neutral flame. Too much reduction can cause the color to become cloudy. Example: Black; use a very oxidizing flame to achieve black, a reducing flame for gray
Again it is suggested that the glassblower experiment with the colors!
Many of the color rods change colors when encased. Encasing a rod is simply covering all the exposed surfaces of the rod with a layer of clear glass. This can be done through three different methods:
1.) Draw lines of clear glass down the rod, being careful not to trap air as you travel around the circumference of the rod
2.) Shrink down a tube of clear glass around the rod; the tube should be just slightly larger than the rod and you should start backwards from the end that is closed, so as not to create high-pressurized hot air pockets. To avoid this altogether, start with both ends open.
3.) Draw a line of color halfway down a clear glass rod and then heat the rod right at the end of the color, as the rod begins to bend, use pliers and fold the clear over the color so it is sandwiched between, creating a line of color between the top layer of clear glass and the bottom layer of clear glass.
In regards to all methods, the last step is to condense the encased portion and then pull out stringers or the size of the rod that you want.
There are numerous Northstar colors that produce different exciting effects when encased are:
NS-03 Multi, NS-04 Dark Multi, NS-14 Irrid, NS-15 Turquesa, NS-24 Transparent Green, NS-27 Green Exotic, NS-28 Blue Exotic, NS-29 Red Exotic, NS-38 Intense Blue Green, NS-41 Butterscotch, NS-44 Caramel, NS-45 Blue Moon, NS-47 Aurora, NS-48 Light Blue Amber Purple, and NS-49 Dark Blue Amber Purple
Northstar's opaque's (ie NS-53 Forest Green, NS-54 Star White, NS-53 Periwinkle, NS-63 Canary, NS-64 Lava) are atmospherically stable colors. When worked properly these colors will not dull, lose intensity, reduce or strike when worked for long durations of time. Opaques must be worked properly in order to prevent overheating and boiling. Working the colors in a soft reducing flame or a cool oxidizing flame is suggested. Encasement of the color is recommended if it is to be used in a larger piece of work, where it will be exposed to greater variances of temperature and diverse flame settings. This is suggested to prevent boiling from occurring and allow the color to be worked longer and faster.
HEAT SENSITIVE COLORS
The opaque colors (White, Jade, Black, Sky Blue, Green Exotic, Blue Exotic and Red Exotic, and to some extent Aqua) are heat sensitive. This means the glass must be treated with more care when heating to avoid boiling. Use either a cooler flame or put the rod in a cooler part of the flame (the edge, or as far away from the torch head as possible). The lampworker must watch the rod and if the glass begins to boil, remove it from the flame immediately. Otherwise, the rod can be "bounced" in and out of the flame to prevent overheating. Also, some Lampworkers report success by inserting the color into a clear tube, then collapsing the tube around the color. The color is the said to be "clad" with the clear glass. This insulates the glass from boiling so easily.
Northstar can be striped, layered, swirled, combed, hobnailed or encased. For interesting effects, try covering one color with another (like Yellow over Ruby) or encase with clear. Frits can be used over other colors for exciting variations.
Direct sunlight is the best light in order to observe the colors. Different types of lighting will produce slightly different effects. Also notice the difference between reflected and transmitted light. In general, Northstar colors are better viewed in reflected light.
THE EXOTIC COLORS
The Exotic colors may be used in the following manner: while working the glass in the flame, use a VERY oxidizing flame. The, just before annealing, while the work is still hot, reduce heavily for several seconds. A metallic, fumed effect will result. The use of a reducing flame during the working stage will produce other interesting effects. All dirt and grease should be removed from exotic colors before use. Even grease from hands can interfere with the metallic fume effect. Exotic colors have a slightly higher COE when used in thick pieces and may cause cracking or checking. Anneal thoroughly.
NS-13 Amber/Purple, NS-26 Double Amber/Purple, NS-48 Light Blue Amber/Purple and NS-49 Dark Blue Amber/Purple continue to be some of the most popular Northstar colors. A "striking" color that also reduces, the effects can range from light yellow to a deep red-amber to various shades of crimson, purple and vermillion.
To get the most exciting effects some reduction is necessary either during or at the end of making your artwork. The trick is to burn off as much of the "haze" as possible when you are finished forming your piece and do the striking and annealing in the kiln. The color should go into the kiln with the oxide "haze" burned off completely.
"Burning off the haze" is a term that means using a hot "pushing", somewhat oxidizing flame to remove the faint layer of reduced oxide on the outer surface of the glass. This layer will form when reduction occurs, which usually does to some extent. If the glass has been worked in a reducing environment and the haze is burned off, more vermillion and crimson will be seen. A more oxidizing environment during the working process will result in ambers and yellows if the haze is not burned off.
When burning off the haze, be aware that this should be done as quickly as possible in order to avoid boiling the glass or slumping the artwork. Some practice may be necessary to train the eye to see this haze and to learn the proper torch settings. This can be subtle. You can actually see the oxide vaporize in the "sweet spot" of the flame. You will also need to experiment with the flame settings to learn the best gas-oxy ratio and best location of the flame for haze burning.
NS-07 Ruby can be flame or kiln struck. It can become over struck and too dark (livery) if struck too hot or too long as sometimes happens when working a piece in the flame for a long period of time.
NS-07L Light Ruby is designed for kiln striking and it may be difficult to get a good strike in the flame. It can be worked a long time in the flame, then kiln annealed for a great Ruby Red.
NS-08 Dark Ruby will retain its color even if thinned or pulled into a stringer. Can be flame struck, but be careful not to overstrike.
It is very important to test all glass colors in your specific application before making an expensive piece or production run. Northstar Glass Inc. strives to make of of their colors compatible and easy to use. However, it is not possible to make all of the colors exactly the same COE. Some colors may check if used in combination with other colors under certain applications.
Certain colors (NS-11 Jade, NS-53 Forest Green, NS-61 Blackberry, and the Exotic Colors in particular) may give the glass worker cracking problems if worked incorrectly. Those colors are best used on the outside of your artwork. If encased with a thick layer of clear, as would be the case in a marble for example, some checking or cracking could occur. Again, please test the color for your application. If you do encase these colors, use as little color as necessary and anneal very carefully.
USING BOILY COLORS
It's a fact that some glass coloring chemicals have a lower boiling point than others. This can cause the color to boil and become bubbly if proper care is not taken to control heating. NS-54 Star White, NS-61 Blackberry, NS-63 Canary, NS-64 Lava and the Exotic Colors are some examples.
Here are some techniques that will help avoid overheating and boiling the glass:
1.) Use a cooler flame, ie less oxygen, but note that this is a reducing flame and if your color is sensitive to atmosphere may be affected. NS-64 Lava will develop gray streaks if reduced heavily. Also turning the oxygen WAY UP, making a very oxidizing, hissing flame has the effect of making the flame cooler.
2.) A flame is usually cooler at the tip and edges of the flame. Work your piece in these areas.
3.) Pass the color through the flame, back and forth. This keeps the glass from being overheated by staying in a hot part of the flame for too long.
4.) When laying down a bead of color, rotate the rod as you lay it down. This presents a cooler side of the rod to the flame continually. This prevents one section of the rod from becoming overheated.
5.) Clad your color with clear glass, which insulates the color from the flame. You can shrink a tube over the color or heat a clear rod and smear an even coat over the color. This can be done on the colored rod before application or you can encase your artwork with clear after the color has been laid down.
6.) In general, if you are using a "boily" color, it is best to gradually heat the color up. This will minimize boiling.