Borosilicate Glass Color Buying Guide: Which Colors to Buy (and Which to Avoid)

Who makes borosilicate glass color?

Here's who each maker is and what they're actually known for:

• Northstar Glassworks (Tigard, Oregon) — The largest and most comprehensive boro color catalog in the US. Makes Borocolour rod, frit, powder, tube, and cane across the Cobalt, Ruby, Amber Purple, Exotic, and Intense Opaque families. Their heat-sensitive color guide, reduction guide, and flame settings guide are the industry reference documents for boro colorwork. Their quick-guide lists every color code with working notes.
• Glass Alchemy — Family-owned maker credited with creating most of the color families now standard in boro. Developed the Neo-Cad Crayon series, the silver-striking Silver Strike line, Dragon's Blood and Half Blood self-striking copper rubies, and the Cobalt series. Quality is excellent; documentation is less standardized than Northstar's.
• Trautman Art Glass (TAG) — Paul Trautman built the world's first commercial colored borosilicate rod factory in the Portland, Oregon area in the mid-1980s and invented the machines and recipes to make boro color rod. TAG is among the finest glass on the market for torch artists, with stringent small-batch quality control. COE 33, annealing temperature 1050°F. Premium priced but consistently excellent.
• Momka's Glass — Founded in 2004 in Seattle by Momka Peeva, a glass chemist who graduated from the Chemistry and Technology University in Sofia, Bulgaria. A founding member of Glass Alchemy, she later co-founded Pacific Borosilicate before launching her own factory. Well-regarded transparents and opaques, available through Nortel and Mountain Glass.
• Origin Glass (BoroStix) — Makes dry-pressed glass powder bars in COE 33 for sampling unusual colors without buying a full rod pound. A useful specialty source, not a primary catalog maker.

Which borosilicate colors are easiest for beginners to work with?

These are the colors beginners reliably succeed with on their first attempts:

• NS-54 Star White (Northstar) — The single most recommended beginner boro color. Atmospherically stable in any flame. Fully opaque creamy white, indispensable as a backing for transparent colors, for sculpture, and stringer work. Heat slowly on initial warm-up to prevent boiling; once glowing it tolerates significant heat. Has been reformulated specifically to make it easier to work.
• NS-76 Onyx (Northstar) — The smoothest, most saturated black in the Northstar palette. Green-based black, not sensitive to reduction. Can be worked hot and long without boiling. Excellent sculptural workhorse — very forgiving for beginners learning heat control.
• NS-001 Cobalt (Northstar) — One of the most forgiving colored rods in the Northstar catalog. Can take a lot of heat and be worked across a wide range of flame settings. Note that cobalt as a family prefers oxidizing flame, but NS-001 is specifically documented as heat-tolerant and workable across broad conditions.
• NS-126 Opaque Aqua (Northstar) — Not susceptible to reduction and not flame-sensitive. A forgiving opal blue-green suited for stringer work and blown work. Keep in a neutral flame for best results.
• NS-023 Pink / NS-031 Lavender / NS-032 Violet (Northstar) — All three are documented as not sensitive to flame atmosphere. Light transparent colors that work simply and predictably — good for learning basic encasement and layering without worrying about flame setting.
• Cobalt-1, 511 (Glass Alchemy) — Smooth and melts with ease, described as very similar to working a clear rod. Retains and soaks heat well. Work in a neutral flame to avoid gray streaks from reduction. One of the most beginner-friendly Glass Alchemy colors.
• Beryl, 833 (Glass Alchemy) — A brownish olive-green transparent. Documented as beginner-friendly WYSIWYG (what you see is what you get). Avoid reduction (causes red streaks). Good for solid-color sculpting.

Which borosilicate colors are hardest to work with, and why?

Cadmium opaques — boil if you rush them

The Northstar Intense Opaque family (NS-63 Canary, NS-65 Cherry, NS-84 Goldenrod, NS-85 Poppy, NS-64 Lava) are the most challenging category in the Northstar catalog. The cadmium compounds in the yellow, red, orange, and gold ranges have extremely low boiling points even in the glassy state. Aggressive or rapid heating causes them to volatilize and boil, destroying the surface. Northstar specifically recommends beginners avoid Intense Opaques entirely until proper flame control is developed.

The Glass Alchemy Crayon series (Neo-Cads: Acid Yellow Crayon, Orange Crayon, Dark Orange Crayon, Chartreuse Crayon, Olive Green Crayon, and others) deliver the highest color saturation for their hue range and remain the standard for bright boro opaques — but they share the same low-boiling-point problem. All Crayon colors contain cadmium and require slow, careful heating in a cool oxidizing flame.

Copper rubies — wrong flame turns them milky

NS-007 Ruby, NS-007L Light Ruby, NS-008 Dark Ruby and Glass Alchemy's Dragon's Blood (1939) and Half Blood (1933) are copper-based striking colors. In a reducing flame, the copper robs oxygen from the surface, changes valence, and deposits as elemental copper — turning the color milky rather than the desired saturated ruby. They also require kiln striking at approximately 1050°F or careful flame striking. Dragon's Blood is self-striking (it develops ruby as it cools), which means beginners can accidentally over-work it before the strike develops.

Atmosphere-reactive colors — dramatic but demanding

The Northstar Exotic family (NS-027 Green Exotic, NS-028 Blue Exotic, NS-029 Red Exotic, NS-047 Aurora) shifts dramatically between oxidizing and reducing flames. Green Exotic is the teaching tool Northstar uses to demonstrate flame chemistry — a metallic sheen develops rapidly in reducing flame, while oxidizing gives a completely different result. These are interesting and visually exciting, but their atmospheric sensitivity makes them unpredictable until you understand flame control well.

The Amber Purple family (NS-013 Amber Purple, NS-026 Double Amber/Purple, NS-048 Light Blue Amber Purple, NS-049 Dark Blue Amber Purple, NS-069 Green Amber Purple) are beloved for their dramatic color range but are notoriously challenging. In oxidizing flame they produce purples; in reducing flame they produce amber or opaque amber — completely different results from the same rod. Understanding precise flame control is a prerequisite before buying any of these.

The silver-base striking colors — Northstar NS-105 Silver Creek, NS-102 Silver Bullet, NS-132 Lokis Lipstick; Glass Alchemy Silver Strike-4 and Silver Strike-5 — react to reduction by turning a foggy cream color as the silver deposits on the glass surface in elemental form. Achieving the desired metallic purples, vermilions, and smoky silvers requires understanding both flame chemistry and the striking temperature window (1075–1125°F for crystal growth). These are multi-step heat-cool-reheat techniques, not beginner colors. See our dedicated color flashing guide for the full process.

What is "striking" a color, and what does "flashing" mean?

There are two main striking mechanisms and two delivery methods:

• Copper ruby striking — Copper rubies (NS Ruby, Dragon's Blood, Half Blood) develop their red through a chemical rearrangement of copper oxide molecules under heat. These colors often ship as pale brownish or gray and only develop their ruby after heat work. The kiln is the standard method: ramp to approximately 1050°F and hold. Flame striking is possible but requires careful control. Reduction turns them milky — keep strictly oxidizing.
• Silver crystal growth — Silver-bearing colors (Northstar Amber Purple family, Silver Creek, Silver Bullet; Glass Alchemy Silver Strike-4 and Silver Strike-5) develop color through actual crystal growth inside the glass. When worked hot, silver crystals dissolve and the glass appears clear. As it cools, silver re-precipitates as crystals. As those crystals grow larger, they interact with different wavelengths of light, producing a predictable color sequence: clear → yellow → orange → ruby red → red-purple → purple → blue → green. The first ambient cooling after working usually only reaches yellow-orange-amber. Achieving purple, blue, and green requires multiple deliberate heat-cool-reheat cycles.
• Flame strike vs kiln strike — Flame striking means cycling the piece between working temperature and the striking zone at the torch. Kiln striking means putting a finished piece in an annealing kiln and ramping it to striking temperature after the piece is shaped. Glass Alchemy recommends flame striking for silver-based colors and kiln striking for copper ruby colors.

The mechanics of this process connect directly to how color-changing glass works — the fumed-silver surface layer on a finished pipe undergoes a related light-interference phenomenon when smoke residue builds up inside.

Why do some colors only appear after the right kiln temperature?

Striking temperatures for silver crystal growth sit just above the annealing point. Borosilicate anneals at approximately 1050°F. Silver crystals grow at approximately 1075–1125°F. To nucleate crystals (create seed sites), cool the piece to approximately 950°F — a slight orange glow — and hold for 20–30 seconds, then gently reheat to 1075–1125°F to grow them.

For kiln striking silver colors, some artists ramp to 1150–1175°F, hold for 10–20 minutes, then ramp down to annealing. Multiple kiln-strike cycles can push the color further along the spectrum — but each re-strike produces increasingly dark and less saturated results. The purple window is very tight and difficult to hold. Our full color flashing guide walks through the practical technique, and the millefiori guide covers related advanced colorwork.

What is the difference between an oxidizing and a reducing flame for boro color?

A flame is characterized by the ratio of fuel (propane or natural gas) to oxygen. There are three types:

• Reducing flame — Insufficient oxygen for complete combustion. The unburned gas particles actively seek oxygen from the glass surface, robbing metal oxide colorants of their bonded oxygen atoms and depositing elemental metal. Visually identified by long wispy candles and a soft bushy flame shape. Deliberately used for specific atmospheric effects on Exotic and Amber Purple colors, but generally destructive to most boro colors.
• Oxidizing flame — Excess oxygen beyond what is needed for combustion. Burns cooler. Identified by a hissing noise, sharp flame candles, and a paler blue color. Maintains the oxygen bond in metal oxide colorants. The default recommended flame for most colored boro work.
• Neutral flame — Equal fuel and oxygen. The hottest flame the torch can produce. Sharp candles and a bright blue glow. Used for working clear boro and for specific colors like Glass Alchemy's copper transparents where neither adding nor removing oxygen is desired.

Flame chemistry also drives the fuming process — understanding the difference between oxidizing and reducing is foundational to silver and gold fuming as well as to other fuming metals.

What colors should a beginner buy first?

Here is the recommended starter palette in priority order:

1. NS-54 Star White (Northstar) — Buy this first, no matter what. Stable in any flame, works as a backing for transparent colors, and teaches you heat management on a forgiving medium.
2. NS-76 Onyx (Northstar) — Essential for line work, contrast, and sculpture. Reduction-insensitive, works hot and long without issue.
3. NS-001 Cobalt (Northstar) — The most beginner-friendly transparent blue. Teaches you how a normal boro transparent behaves. Prefers oxidizing but is documented as heat-tolerant across a wide range.
4. NS-126 Opaque Aqua (Northstar) — Stable opal blue-green. Not reduction-sensitive. Adds color variety without adding technique requirements.
5. NS-023 Pink or NS-031 Lavender (Northstar) — Not flame-sensitive. Easy light transparents that teach layering and encasement without complexity.
6. Glass Alchemy Cobalt-1, 511 (optional first addition) — Smooth like clear glass. Introduces you to Glass Alchemy's feel and quality without any of their reactive or striking colors.
7. Glass Alchemy Half Blood, 1933 (optional, after 20–30 hours) — The lighter copper ruby, teaches the heat-cool-observe cycle for striking. Only when you are comfortable with flame control.

Once your spoon pipes are clean and your flame control is reliable, the natural progression into color is to learn fuming first — silver and gold fuming teach you flame chemistry and atmospheric control at low cost, and the results are visually dramatic. See the fuming guide for where to start and the boro glass sizes guide for the right tubing and rod diameter for each technique.

How do you buy borosilicate color rod without wasting money?

The practical buying details that save beginners the most money:

• Rod diameter — Color rods typically come in 5–7 mm diameter (sometimes 8 mm for heavier blown work). Larger diameter rods hold more color per inch and are easier to gather from for blown work. Most beginners buy standard 6–7 mm first-quality rods.
• Buy by weight, not piece — Color rod is sold by the pound or fraction. Most suppliers sell in 1/4 lb or 1/2 lb increments. Start at 1/2 lb per color. Buying 1 lb or more typically reduces the per-ounce price significantly once you know a color works for you.
• Quality grades — Northstar sells First Quality, Odd Quality (slight color variation but usable), and Second Quality (more significant deviation). Beginners can save money on Second Quality for practice colors but should buy First Quality for colors where hue accuracy matters.
• Sample packs — Mountain Glass Arts sells boro color sample packs in half-length rods. This is the best way to try a wide range of colors cheaply before committing to full pounds. Delphi Glass also sells a Boro Batch Half Length Sample Pack.
• Avoid Amazon for named colors — Generic COE 33 rods sold on Amazon are not from Northstar, Glass Alchemy, TAG, or Momka's. Their color stability, COE accuracy, and working characteristics are unknown. Buy direct from Northstar or Glass Alchemy, or from established retailers: Mountain Glass Arts, Frantz Art Glass, Glass House Supply, or Delphi Glass.
• Storage — Store rods horizontally or in vertical tubes away from direct sunlight. Some UV-reactive boro colors can shift with prolonged UV exposure. Keep heat-sensitive colors (Intense Opaques, Crayon series) cool and dry. Do not store rods where they can roll and chip — chips create seeds and bubbles in your work. Many artists use PVC tubes capped at both ends.
• Plan for waste — Heat-sensitive colors (cadmium opaques especially) have a higher rate of boiling or bubbling when learning. Build in at least 20–30% extra when buying your first pound of Intense Opaques or Crayons — you will lose material to technique until flame control is solid.

Borosilicate color comparison table