Northstar Glass User's Manuel & Tips
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Northstar Glass User’s Manuel & Tips Frantz Art Glass & Supply 130 West Corporate Road Shelton, WA 98584 USA Toll free 1-800-839-6712 Fax 360-427-5866 [email protected] www.FrantzArtGlass.com Page 1 of 19 Northstar Use Info.docx NOTES ON THE COMPATIBILITY AND USE OF NORTHSTAR BRAND BOROSILICATE GLASS by Robert A. Mickelsen 4/29/94 This document contains some of my personal observations and experiences with Northstar Borocolour colored glass. These are strictly my feelings and opinions and do not necessarily reflect the opinions of the manufacturer or anyone else for that matter. Northstar colors can be roughly divided into two categories: colors that strike and colors that do not strike. They can be further categorized into several color groups: reds, oranges, and yellows; the cobalt family; transparent and multi greens; opacified colors; exotics; and what I call 'pastel' colors. These categories are somewhat arbitrary and but I list them here because it demonstrates how many of the Northstar colors are derivative of each other. I will discuss them within the context of these categories. REDS, ORANGES, AND YELLOWS Northstar Ruby was the first Northstar color I tried. It is a striking color that turns an intense transparent red when re-heated. This color used to have a lot of seeds and bubbles in it, but has gotten much cleaner in recent years. Just recently, Paul Trautman has sent me samples of a 'new improved' Ruby that is cleaner and less seedy than ever before. Furthermore, this new Ruby does not 'overstrike' (turn opaque brick-red) as easily as the old Ruby did, so you can work it more. Paul says he is changing all the Ruby and Orange colors over to this new technology. Ruby (NS07) can be heated back to clear and re-struck many times without damaging or devitrifying the glass. For best results, Ruby should be worked in a neutral to slightly oxidizing flame and, if possible, placed in the annealing oven while still clear. This will result in a very transparent red. Ruby goes very well with Cobalt Blue, Black, Turbo Cobalt, White, Green, and Aqua. It makes excellent casing material, but is only fair for frit and trailing. I generally use Dark Ruby (NS08) for those types of applications. Dark Ruby strikes almost black if applied thicker than 1/8" and annealed while still clear. It's intensity makes it great for very thin trailing and fine frit and it makes very nice twisted lip wraps. I also use it for shards because it can be blown very thin and will still strike deep red. I simulate black on larger pieces of glass by casing Dark Ruby over clear with a layer of Cobalt Blue (NS01) over that. Northstar Orange (NS05) is one of my favorite colors, but it can be aggravating to use because there seems to be a broad variation in intensity from batch to batch. You have to be careful not to use two different rods on the same piece because, as often as not, they will not strike the same, and could ruin the piece. This variation is due primarily to continuing attempts by Northstarþ to improve their formulas. Still, the color is one of the best Northstarþ makes. The intensity ranges from a pale transparent orange to a deep almost opaque coral color. This color is clearly a mixture of Ruby (NS07) and Yellow (NS09). Orange tends to strike with a slight opalescence that increases the more you work the rod. This opalescence will appear first with the orange highlights taking longer to strike. The opalescence can be eliminated by reheating the color clear and then striking the piece in the oven, which will result in a transparent orange. Like Ruby, it Page 2 of 19 Northstar Use Info.docx can be heated back to clear and re-struck many times without any ill effects on the glass. Dark Orange (NS06) is a more consistent color. Like Dark Ruby (NS08), it is very good for trailing, shards, frit, and other applications that are very thin. Also like the ruby, the oranges have had a problem with seeds and bubbles in the past, but Paul tells me that the new technology will apply to them as well and should clear the problem up. Both oranges go well with any of the green colors and look wonderful with Black. Northstar Yellow (NS09) is similar to Orange in its behavior. I do not use much Yellow, but I have heard that very interesting effects can be achieved by layering Yellow over other striking colors like multi-green (NS03). Yellow tends to stay pretty clear, but if it is re-heated in a reducing flame it will take on the swirly opalescence that is characteristic of yellows and oranges. This opalescence can be avoided by heating the color back to clear before placing the piece in the annealing oven. If annealed clear, the result will be very transparent yellow. The extra Light Yellow (NS34) is even lighter than Yellow. It was designed primarily for overlaying other colors. These rods are so light I have gotten them confused with my clear pyrex stock from time to time. Layering Yellow or light Yellow over Ruby will yield very pretty violet and vermillon highlights. Amber-Purple (NS13) really needs its own classification, but I am putting it with the reds, oranges, and yellows because it is most closely related to Yellow. But Yellow it is not. Amber- Purple is one of the most unique and difficult to learn of the Northstar colors. Like Orange, this color tends to vary from batch to batch, so you don't want to use two different rods on one piece. The rods look deep yellow when you buy them, but when they are re-heated, they take on a beautiful opalescent violet color. This color is more easily viewed in direct light. If back lit, the glass will look more amber in color... thus its unlikely name. I have had difficulty in getting consistent results with Amber-Purple, but I still use it extensively. The Northstar catalogue says to work the color in an oxidizing flame and then reduce to get the purple highlights, but it is not that simple. Amber-Purple is a color that changes its characteristics the longer you work it. If used in a procedure that only involves heating it one time, it is quite easy to strike it purple. But, more often than not, you must repeatedly heat and re-heat the glass and then Amber-Purple seems to get overpowered by the opalescence in the glass. It becomes more and more opaque until it is actually a deep custard color. When it reaches this stage, it is much more difficult to strike it with purple highlights. If you encase Amber-Purple in clear glass, it is impossible to get purple highlights. Instead the glass becomes an opaque custard color, which is not bad actually, so I case it all the time! Amber Purple goes very well with Orange, Black, and Jade Green. It is intense enough to make good frit and trailing, but makes only fair shards. It is excellent for sculpting, especially if you can achieve final shape with only one or two heatings so you can strike it deep purple. THE COBALT FAMILY The cobalt family is the largest group of colors. No less than nine Northstarþ colors are in this family: Cobalt Blue (NS01), Irrid Blue (NS14), Turquesa (NS15), Black (NS16), Light Cobalt Blue (NS19), Dark Cobalt Blue (NS20), Turbo Cobalt (NS33), Black Hole (NS35), and Intense Blue-Green (NS38). Page 3 of 19 Northstar Use Info.docx There are four different intensities of Northstar Cobalt Blue: Regular Cobalt (NS01), Light Cobalt (NS19), Dark Cobalt (NS20), and Turbo-Cobalt (NS33). But they all share the same general characteristics. The cobalt colors tend to be very clean and devoid of any bubbles or seeds or even striations from uneven mixing. The lighter cobalts are extremely clear and retain that clarity even when heated and re-heated extensively. The darker cobalts are somewhat prone to reducing and should therefore be heated in an oxidizing flame. The darker the cobalt, the more pronounced this problem becomes and therefore, the more oxidizing your flame should be. I use Regular Cobalt for casing and combining with other colors. It is lovely for sculpture and any decorations over 1/8" thick. Light Cobalt is also a beautiful color, very transparent, and is great for casing and sculptures, but should be used no less that 1/4" thick. Dark Cobalt is better for thinner decorations like shards and thick trailing, but is still too light for trailing or frit. It makes very good lip wraps. The darkest cobalt, Turbo-Cobalt, is a terrific substitute for black. It will not look blue until it is drawn thinner than 1/32", but has none of the drawbacks of black and black hole like bubbles and a tendency to bloom. Turbo Cobalt must be worked in a highly oxidizing flame however, or it will reduce and show grey streaks that, once they appear, are difficult to heat out. Three colors of the cobalt family are striking colors. They are Irrid Blue (NS14), Turquesa (NS15), and Intense Blue-Green (NS38). They are all essentially variations of one another with Irrid being the lightest and Blue-Green being the darkest. They are all a combination of Cobalt and Yellow in varying intensities. Like the cobalts, they tend to be very clean colors, without any bubbles or seeds. These colors are wonderful for casing because of the beautiful way they strike.